Astronomers find bounty of failed stars: One youngster only six times heftier than Jupiter

ScienceDaily (Oct. 11, 2011) — A University of Toronto-led team of astronomers has discovered over two dozen new free-floating brown dwarfs, including a lightweight youngster only about six times heftier than Jupiter, that reside in two young star clusters. What's more, one cluster contains a surprising surplus of them, harbouring half as many of these astronomical oddballs as normal stars.

"Our findings suggest once again that objects not much bigger than Jupiter could form the same way as stars do. In other words, nature appears to have more than one trick up its sleeve for producing planetary mass objects," says Professor Ray Jayawardhana, Canada Research Chair in Observational Astrophysics at the University of Toronto and leader of the international team that made the discovery.

Brown dwarfs straddle the boundary between stars and planets. Sometimes described as failed stars, they glow brightly when young, from the heat of formation, but cool down over time and end up with atmospheres that exhibit planet-like characteristics. Scientists think that most brown dwarfs may have formed like stars, in isolation from contracting gas clouds, but some of the puniest free-floaters may have formed like planets around a star and later ejected.

The findings come from observations using the Subaru Telescope in Hawaii and the Very Large Telescope (VLT) in Chile during the Substellar Objects in Nearby Young Clusters (SONYC) survey. Astronomers took extremely deep images of the NGC 1333 and rho Ophiuchi star clusters with Subaru at both optical and infrared wavelengths. Once they identified candidate brown dwarfs from the very red colors, the research team confirmed them with spectra taken at Subaru and the VLT. The team's findings will be reported in two upcoming papers in the Astrophysical Journal and presented this week at a scientific conference in Garching, Germany.

The six-Jupiter-mass brown dwarf found in the NGC 1333 cluster is one of the least massive free-floating objects known. "Its mass is comparable to those of giant planets, yet it doesn't circle a star. How it formed is a mystery," said Aleks Scholz of the Dublin Institute of Advanced Studies in Ireland, lead author of one paper and a former postdoctoral fellow at the University of Toronto.

Several other newly identified brown dwarfs in both NGC 1333 and rho Ophiuchi clusters have masses below 20 times that of Jupiter.

"Brown dwarfs seem to be more common in NGC 1333 than in other young star clusters. That difference may be hinting at how different environmental conditions affect their formation," says University of Toronto's Koraljka Muzic, lead author of the second paper.

"We could not have made these exciting discoveries if not for the remarkable capabilities of Subaru and the VLT. Instruments that can image large patches of the sky and take hundreds of spectra at once are key to our success," said co-author Motohide Tamura of the National Astronomical Observatory of Japan.

Other co-authors of the two papers are Vincent Geers of ETH Zurich in Switzerland, also a former UofT postdoc, and Mariangela Bonavita of the University of Toronto.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Toronto.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astrophysicists find evidence of black holes' destruction of stars

ScienceDaily (Oct. 12, 2011) — Astrophysicists have found evidence of black holes destroying stars, a long-sought phenomenon that provides a new window into general relativity. The research, reported in the latest issue of the Astrophysical Journal, also opens up a method to search for the possible existence of a large population of presently undetectable "intermediate mass" black holes which are hypothesized to be precursors to the super-massive black holes at the centers of most large galaxies.

The study was carried out primarily by Glennys Farrar and Sjoert van Velzen at New York University's Center for Cosmology and Particle Physics, and also included the following researchers: Suvi Gezari of Johns Hopkins University's Department of Physics and Astronomy; Linda Ostman of Spain's Universitat Autònoma de Barcelona; Nidia Morrell of the Las Campanas Observatory in Chile; Dennis Zaritsky of the University of Arizona; Matthew Smith of South Africa's University of Cape Town; Joseph Gelfand of NYU-Abu Dhabi; and Andrew Drake of Caltech. Van Velzen is currently a doctoral candidate at Radboud University in the Netherlands.

Cosmologists have calculated that, on occasion, a star's orbit will be disturbed in such a way that it passes very near the super-massive black hole at the center of its galaxy -- but not so close that it is captured whole. Such a star will be torn apart by the extreme tidal forces it experiences: the force of gravity on the near side of the star is so much stronger than that on the far side that the gravitational force holding the star together is overwhelmed, causing the star to simply come apart. While some of the star's matter falls into the black hole, much of it continues in chaotic orbits, crashing into itself and producing intense radiation lasting days to months. These phenomena are called stellar tidal disruption flares, or TDFs.

Although discovering evidence of TDFs has been a high priority of astrophysicists for many years, and several possible examples have been found using X-ray and UV satellites, discovering TDFs in a large-scale, systematic survey using ground-based optical telescopes as has now been achieved, is critical to controlling bias and avoiding misidentifications.

The difficulty in detecting TDFs is largely due to the challenge of distinguishing them from more common types of flares such as supernovae. (For every TDF there are about 1000 supernovae.) In addition, some super-massive black holes have an "accretion disk" surrounding them -- gas and dust, often left from an earlier merger with another galaxy -- which is continuously feeding the hole. Such accreting black holes are usually evident from the bright emission they produce and are known as quasars or Active Galactic Nuclei (AGN). However, a hiccup in the accretion of an undetected active black hole could produce a flare that might be mistakenly identified as a TDF.

The researchers on the Astrophysical Journal study uncovered sound evidence for the presence of two TDFs through a rigorous analysis of archival data from the Sloan Digital Sky Survey (SDSS).

To do so, they sifted through voluminous SDSS data, in which more than 2 million galaxies were repeatedly observed over 10 years. By very carefully registering the images and looking at differences between consecutive images, they obtained a sample of 342 intense and well-measured flares.

Of these, almost all could be classified into supernovae and AGN flares. However, two cases were left that did not fit either classification. By relying on multi-year observations, the researchers could see that the two flares' host galaxies showed no other flaring activity, as would be the case if the flares came from a hidden variable AGN. This means the possibility these two flares were produced by undetected AGNs is extremely small.

In addition, the researchers located these flares at the nucleus of their galaxy with high precision, which reduces the likelihood that they are supernovae to less than 1 percent since supernovae are randomly distributed through galaxies.

Finally, the properties of these flares are very different from flares of AGNs and supernovae -- and their spectra are unlike any supernovae observed to date. Supernovae flares are characteristically very blue at first but become red as they cool and rapidly decay, whereas the TDF flares are very blue throughout -- slowly decaying without changing color. This behavior is consistent with expectations for a TDF -- the debris from the star should rapidly form an accretion disk and look like a short-lived AGN.

Sjoert van Velzen, the study's lead author, was a Dutch first-year graduate student who came to NYU to work under the direction of Glennys Farrar, a Professor of Physics at NYU and senior scientist of the project. Van Velzen is now completing his Ph. D. in Holland.

About his first encounter with real scientific work, van Velzen says, "Searching through 2.6 million galaxies was actually a lot of fun -- there is so much to discover! Based on our search criteria and observing two TDFs that met those criteria, the rate of TDFs is about once per 100,000 years, per galaxy. It's quite thrilling to have been able to make such a measurement."

"The next step is to develop models to explain in detail the flares' properties and duration, and address the question of whether TDFs could be responsible for producing Ultrahigh Energy Cosmic Rays, whose sources have been elusive up to now," says Farrar. "It is very exciting that we are on the verge of obtaining a large and better-observed sample of TDFs to study -- though a more sensitive search of SDSS archival data and the new generation of transient surveys which will observe more flares in real-time and with multi-wavelength follow-up. A large sample will be invaluable to understanding many outstanding questions in astrophysics."

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Sjoert van Velzen, Glennys R. Farrar, Suvi Gezari, Nidia Morrell, Dennis Zaritsky, Linda Ostman, Mathew Smith, Joseph Gelfand, Andrew J. Drake. Optical discovery of probable stellar tidal disruption flares. Astrophysical Journal, 2011 (in press) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astronomers explain blue stragglers: How do mysterious stars stay so young?

ScienceDaily (Oct. 20, 2011) — Mysterious "blue stragglers" are old stars that appear younger than they should be: they burn hot and blue. Several theories have attempted to explain why they don't show their age, but, until now, scientists have lacked the crucial observations with which to test each hypothesis.

Armed with such observational data, two astronomers from Northwestern University and the University of Wisconsin-Madison report that a mechanism known as mass transfer explains the origins of the blue stragglers. Essentially, a blue straggler eats up the mass, or outer envelope, of its giant-star companion. This extra fuel allows the straggler to continue to burn and live longer while the companion star is stripped bare, leaving only its white dwarf core.

The scientists report their evidence in a study to be published Oct. 20 by the journal Nature.

The majority of blue stragglers in their study are in binaries: they have a companion star. "It's really the companion star that helped us determine where the blue straggler comes from," said Northwestern astronomer Aaron M. Geller, first author of the study. "The companion stars orbit at periods of about 1,000 days, and we have evidence that the companions are white dwarfs. Both point directly to an origin from mass transfer."

Geller is the Lindheimer Postdoctoral Fellow in the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the department of physics and astronomy in Northwestern's Weinberg College of Arts and Sciences. Robert Mathieu, professor of astronomy and chair of the astronomy department at UW-Madison, is co-author of the study.

The astronomers studied the NGC 188 open cluster, which is in the constellation Cepheus, situated in the sky near Polaris, the North Star. This cluster is one of the most ancient open star clusters, but it features these mysterious young blue stragglers.

The cluster has around 3,000 stars, all about the same age, and has 21 blue stragglers. Geller and Mathieu are the first to use detailed observational data from the WIYN Observatory in Tucson, Ariz., of the blue stragglers in NGC 188.

They used the information to analyze and compare the three main theories of blue straggler formation: collisions between stars, mergers of stars and mass transfer from one star to another. The only one left standing was the theory of mass transfer.

The light from the blue stragglers' companion stars is not actually visible in Geller and Mathieu's observations. While the companions haven't been seen directly, their effect on the blue stragglers is evident: each companion pulls gravitationally on its blue straggler and creates a "wobble" as it orbits, and this allows astronomers to measure the mass of the companion stars. The WIYN data show that each companion star is about half the mass of the sun, which is consistent with a white dwarf.

The other two origin theories -- collisions and mergers -- require the companion stars to be more massive than what is observed. In fact, in both scenarios, some of the companion stars could be bright enough to be visible in the WIYN data, which is not the case.

"We think we have a good understanding of stellar evolution, but it doesn't predict blue stragglers," Geller said. "People have been trying to explain the origin of blue stragglers since their discovery in 1953, and now we have the detailed observations needed to identify how they were created. I've always enjoyed trying to get to the bottom of a mystery."

"As so often happens in astronomy, it is the objects that you don't see that provide the critical clues," said Mathieu, an expert on binary stars. "Now we will use the Hubble Space Telescope to search for the ultraviolet light in which white dwarf secondary stars shine."

Geller, Mathieu and their colleagues will have, in about a year's time, observations from Hubble that will tell them if the blue stragglers' companions are indeed white dwarfs.

The NGC 188 data set was collected during the last decade by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz., as part of the WIYN Open Cluster Study led by Mathieu. The observatory is operated by UW-Madison, Indiana University, Yale University and the National Optical Astronomical Observatory (NOAO).

NOAO is operated by the Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

The National Science Foundation, the Wisconsin Space Grant Consortium and the Lindheimer Fellowship at Northwestern University supported the research.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Northwestern University. The original article was written by Megan Fellman.

Note: ScienceDaily reserves the right to edit materials for content and length. For further information, please contact the source cited above.

Journal Reference:

Aaron M. Geller, Robert D. Mathieu. A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions. Nature, 2011; 478 (7369): 356 DOI: 10.1038/nature10512

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astronomers explain blue stragglers: How do mysterious stars stay so young?

ScienceDaily (Oct. 20, 2011) — Mysterious "blue stragglers" are old stars that appear younger than they should be: they burn hot and blue. Several theories have attempted to explain why they don't show their age, but, until now, scientists have lacked the crucial observations with which to test each hypothesis.

Armed with such observational data, two astronomers from Northwestern University and the University of Wisconsin-Madison report that a mechanism known as mass transfer explains the origins of the blue stragglers. Essentially, a blue straggler eats up the mass, or outer envelope, of its giant-star companion. This extra fuel allows the straggler to continue to burn and live longer while the companion star is stripped bare, leaving only its white dwarf core.

The scientists report their evidence in a study to be published Oct. 20 by the journal Nature.

The majority of blue stragglers in their study are in binaries: they have a companion star. "It's really the companion star that helped us determine where the blue straggler comes from," said Northwestern astronomer Aaron M. Geller, first author of the study. "The companion stars orbit at periods of about 1,000 days, and we have evidence that the companions are white dwarfs. Both point directly to an origin from mass transfer."

Geller is the Lindheimer Postdoctoral Fellow in the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the department of physics and astronomy in Northwestern's Weinberg College of Arts and Sciences. Robert Mathieu, professor of astronomy and chair of the astronomy department at UW-Madison, is co-author of the study.

The astronomers studied the NGC 188 open cluster, which is in the constellation Cepheus, situated in the sky near Polaris, the North Star. This cluster is one of the most ancient open star clusters, but it features these mysterious young blue stragglers.

The cluster has around 3,000 stars, all about the same age, and has 21 blue stragglers. Geller and Mathieu are the first to use detailed observational data from the WIYN Observatory in Tucson, Ariz., of the blue stragglers in NGC 188.

They used the information to analyze and compare the three main theories of blue straggler formation: collisions between stars, mergers of stars and mass transfer from one star to another. The only one left standing was the theory of mass transfer.

The light from the blue stragglers' companion stars is not actually visible in Geller and Mathieu's observations. While the companions haven't been seen directly, their effect on the blue stragglers is evident: each companion pulls gravitationally on its blue straggler and creates a "wobble" as it orbits, and this allows astronomers to measure the mass of the companion stars. The WIYN data show that each companion star is about half the mass of the sun, which is consistent with a white dwarf.

The other two origin theories -- collisions and mergers -- require the companion stars to be more massive than what is observed. In fact, in both scenarios, some of the companion stars could be bright enough to be visible in the WIYN data, which is not the case.

"We think we have a good understanding of stellar evolution, but it doesn't predict blue stragglers," Geller said. "People have been trying to explain the origin of blue stragglers since their discovery in 1953, and now we have the detailed observations needed to identify how they were created. I've always enjoyed trying to get to the bottom of a mystery."

"As so often happens in astronomy, it is the objects that you don't see that provide the critical clues," said Mathieu, an expert on binary stars. "Now we will use the Hubble Space Telescope to search for the ultraviolet light in which white dwarf secondary stars shine."

Geller, Mathieu and their colleagues will have, in about a year's time, observations from Hubble that will tell them if the blue stragglers' companions are indeed white dwarfs.

The NGC 188 data set was collected during the last decade by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz., as part of the WIYN Open Cluster Study led by Mathieu. The observatory is operated by UW-Madison, Indiana University, Yale University and the National Optical Astronomical Observatory (NOAO).

NOAO is operated by the Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

The National Science Foundation, the Wisconsin Space Grant Consortium and the Lindheimer Fellowship at Northwestern University supported the research.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Northwestern University. The original article was written by Megan Fellman.

Note: ScienceDaily reserves the right to edit materials for content and length. For further information, please contact the source cited above.

Journal Reference:

Aaron M. Geller, Robert D. Mathieu. A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions. Nature, 2011; 478 (7369): 356 DOI: 10.1038/nature10512

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Ancient supernovas discovered: 10-billion-year-old exploding stars were a source of Earth's iron, researchers say

ScienceDaily (Oct. 7, 2011) — Supernovas -- stars in the process of exploding -- open a window onto the history of the elements of Earth's periodic table as well as the history of the universe. All of those heavier than oxygen were formed in nuclear reactions that occurred during these explosions.

The most ancient explosions, far enough away that their light is reaching us only now, can be difficult to spot. A project spearheaded by Tel Aviv University researchers has uncovered a record-breaking number of supernovas in the Subaru Deep Field, a patch of sky the size of a full moon. Out of the 150 supernovas observed, 12 were among the most distant and ancient ever seen.

The discovery sharpens our understanding of the nature of supernovas and their role in element formation, say study leaders Prof. Dan Maoz, Dr. Dovi Poznanski and Or Graur of TAU's Department of Astrophysics at the Raymond and Beverly Sackler School of Physics and Astronomy. These "thermonuclear" supernovas in particular are a major source of iron in the universe.

The research, which appears in the Monthly Notices of the Royal Astronomical Society this month, was done in collaboration with teams from a number of Japanese and American institutions, including the University of Tokyo, Kyoto University, the University of California Berkeley, and Lawrence Berkeley National Laboratory.

A key element of the universe

Supernovas are nature's "element factories." During these explosions, elements are both formed and flung into interstellar space, where they serve as raw materials for new generations of stars and planets. Closer to home, says Prof. Maoz, "these elements are the atoms that form the ground we stand on, our bodies, and the iron in the blood that flows through our veins." By tracking the frequency and types of supernova explosions back through cosmic time, astronomers can reconstruct the universe's history of element creation.

In order to observe the 150,000 galaxies of the Subaru Deep Field, the team used the Japanese Subaru Telescope in Hawaii, on the 14,000-foot summit of the extinct Mauna Kea volcano. The telescope's light-collecting power, sharp images, and wide field of view allowed the researchers to overcome the challenge of viewing such distant supernovas.

By "staring" with the telescope at the Subaru Deep Field, the faint light of the most distant galaxies and supernovas accumulated over several nights at a time, forming a long and deep exposure of the field. Over the course of observations, the team "caught" the supernovas in the act of exploding, identifying 150 supernovas in all.

Sourcing man's life-blood

According to the team's analysis, thermonuclear type supernovas, also called Type-la, were exploding about five times more frequently 10 billion years ago than they are today. These supernovas are a major source of iron in the universe, the main component of Earth's core and an essential ingredient of the blood in our bodies.

Scientists have long been aware of the "universal expansion," the fact that galaxies are receding from one another. Observations using Type-Ia supernovas as beacons have shown that the expansion is accelerating, apparently under the influence of a mysterious "dark energy" -- the 2011 Nobel Prize in Physics will be awarded to three astronomers for this work. However, the nature of the supernovas themselves is poorly understood. This study improves our understanding by revealing the range of the ages of the stars that explode as Type-Ia supernovas. Eventually, this will enhance their usefulness for studying dark energy and the universal expansion, the researchers explain.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Friends of Tel Aviv University.

Journal Reference:

K. Maguire, M. Sullivan, R. C. Thomas, P. Nugent, D. A. Howell, A. Gal-Yam, I. Arcavi, S. Ben-Ami, S. Blake, J. Botyanszki, C. Buton, J. Cooke, R. S. Ellis, I. M. Hook, M. M. Kasliwal, Y.-C. Pan, R. Pereira, P. Podsiadlowski, A. Sternberg, N. Suzuki, D. Xu, O. Yaron, J. S. Bloom, S. B. Cenko, S. R. Kulkarni, N. Law, E. O. Ofek, D. Poznanski, R. M. Quimby. PTF10ops - a subluminous, normal-width light curve Type Ia supernova in the middle of nowhere. Monthly Notices of the Royal Astronomical Society, 2011; DOI: 10.1111/j.1365-2966.2011.19526.x

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astrophysicists find evidence of black holes' destruction of stars

ScienceDaily (Oct. 12, 2011) — Astrophysicists have found evidence of black holes destroying stars, a long-sought phenomenon that provides a new window into general relativity. The research, reported in the latest issue of the Astrophysical Journal, also opens up a method to search for the possible existence of a large population of presently undetectable "intermediate mass" black holes which are hypothesized to be precursors to the super-massive black holes at the centers of most large galaxies.

The study was carried out primarily by Glennys Farrar and Sjoert van Velzen at New York University's Center for Cosmology and Particle Physics, and also included the following researchers: Suvi Gezari of Johns Hopkins University's Department of Physics and Astronomy; Linda Ostman of Spain's Universitat Autònoma de Barcelona; Nidia Morrell of the Las Campanas Observatory in Chile; Dennis Zaritsky of the University of Arizona; Matthew Smith of South Africa's University of Cape Town; Joseph Gelfand of NYU-Abu Dhabi; and Andrew Drake of Caltech. Van Velzen is currently a doctoral candidate at Radboud University in the Netherlands.

Cosmologists have calculated that, on occasion, a star's orbit will be disturbed in such a way that it passes very near the super-massive black hole at the center of its galaxy -- but not so close that it is captured whole. Such a star will be torn apart by the extreme tidal forces it experiences: the force of gravity on the near side of the star is so much stronger than that on the far side that the gravitational force holding the star together is overwhelmed, causing the star to simply come apart. While some of the star's matter falls into the black hole, much of it continues in chaotic orbits, crashing into itself and producing intense radiation lasting days to months. These phenomena are called stellar tidal disruption flares, or TDFs.

Although discovering evidence of TDFs has been a high priority of astrophysicists for many years, and several possible examples have been found using X-ray and UV satellites, discovering TDFs in a large-scale, systematic survey using ground-based optical telescopes as has now been achieved, is critical to controlling bias and avoiding misidentifications.

The difficulty in detecting TDFs is largely due to the challenge of distinguishing them from more common types of flares such as supernovae. (For every TDF there are about 1000 supernovae.) In addition, some super-massive black holes have an "accretion disk" surrounding them -- gas and dust, often left from an earlier merger with another galaxy -- which is continuously feeding the hole. Such accreting black holes are usually evident from the bright emission they produce and are known as quasars or Active Galactic Nuclei (AGN). However, a hiccup in the accretion of an undetected active black hole could produce a flare that might be mistakenly identified as a TDF.

The researchers on the Astrophysical Journal study uncovered sound evidence for the presence of two TDFs through a rigorous analysis of archival data from the Sloan Digital Sky Survey (SDSS).

To do so, they sifted through voluminous SDSS data, in which more than 2 million galaxies were repeatedly observed over 10 years. By very carefully registering the images and looking at differences between consecutive images, they obtained a sample of 342 intense and well-measured flares.

Of these, almost all could be classified into supernovae and AGN flares. However, two cases were left that did not fit either classification. By relying on multi-year observations, the researchers could see that the two flares' host galaxies showed no other flaring activity, as would be the case if the flares came from a hidden variable AGN. This means the possibility these two flares were produced by undetected AGNs is extremely small.

In addition, the researchers located these flares at the nucleus of their galaxy with high precision, which reduces the likelihood that they are supernovae to less than 1 percent since supernovae are randomly distributed through galaxies.

Finally, the properties of these flares are very different from flares of AGNs and supernovae -- and their spectra are unlike any supernovae observed to date. Supernovae flares are characteristically very blue at first but become red as they cool and rapidly decay, whereas the TDF flares are very blue throughout -- slowly decaying without changing color. This behavior is consistent with expectations for a TDF -- the debris from the star should rapidly form an accretion disk and look like a short-lived AGN.

Sjoert van Velzen, the study's lead author, was a Dutch first-year graduate student who came to NYU to work under the direction of Glennys Farrar, a Professor of Physics at NYU and senior scientist of the project. Van Velzen is now completing his Ph. D. in Holland.

About his first encounter with real scientific work, van Velzen says, "Searching through 2.6 million galaxies was actually a lot of fun -- there is so much to discover! Based on our search criteria and observing two TDFs that met those criteria, the rate of TDFs is about once per 100,000 years, per galaxy. It's quite thrilling to have been able to make such a measurement."

"The next step is to develop models to explain in detail the flares' properties and duration, and address the question of whether TDFs could be responsible for producing Ultrahigh Energy Cosmic Rays, whose sources have been elusive up to now," says Farrar. "It is very exciting that we are on the verge of obtaining a large and better-observed sample of TDFs to study -- though a more sensitive search of SDSS archival data and the new generation of transient surveys which will observe more flares in real-time and with multi-wavelength follow-up. A large sample will be invaluable to understanding many outstanding questions in astrophysics."

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by New York University.

Journal Reference:

Sjoert van Velzen, Glennys R. Farrar, Suvi Gezari, Nidia Morrell, Dennis Zaritsky, Linda Ostman, Mathew Smith, Joseph Gelfand, Andrew J. Drake. Optical discovery of probable stellar tidal disruption flares. Astrophysical Journal, 2011 (in press) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Clearing the 'cosmic fog' of the early universe: Massive stars may be responsible

ScienceDaily (Oct. 13, 2011) — The space between the galaxies wasn't always transparent. In the earliest times, it was an opaque, dense fog. How it cleared is an important question in astronomy. New observational evidence from the University of Michigan shows how high energy light from massive stars could have been responsible.

Astronomers believed that early star-forming galaxies could have provided enough of the right kind of radiation to evaporate the fog, or turn the neutral hydrogen intergalactic medium into the charged hydrogen plasma that remains today. But they couldn't figure out how that radiation could escape a galaxy. Until now.

Jordan Zastrow, a doctoral astronomy student, and Sally Oey, a U-M astronomy professor, observed and imaged the relatively nearby NGC 5253, a dwarf starburst galaxy in the southern constellation Centaurus. Starburst galaxies, as their name implies, are undergoing a burst of intense star formation. While rare today, scientists believe they were very common in the early universe.

The researchers used special filters to see where and how the galaxy's extreme ultraviolet radiation, or UV light, was interacting with nearby gas. They found that the UV light is, indeed, evaporating gas in the interstellar medium. And it is doing so along a narrow cone emanating from the galaxy.

A paper on their work is published Oct. 12 in Astrophysical Journal Letters.

"We are not directly seeing the ultraviolet light. We are seeing its signature in the gas around the galaxy," Zastrow said.

In starburst galaxies, a superwind from these massive stars can clear a passageway through the gas in the galaxy, allowing the radiation to escape, the researchers said.

The shape of the cone they observed could help explain why similar processes in other galaxies have been difficult to detect.

"This feature is relatively narrow. The opening that is letting the UV light out is small, which makes this light challenging to detect. We can think of it as a lighthouse. If the lamp is pointed toward you, you can see the light. If it's pointed away from you, you can't see it," Zastrow said. "We believe the orientation of the galaxy is important as to whether we can detect escaping UV radiation."

The findings could help astronomers understand how the earliest galaxies affected the universe around them.

Also contributing were researchers from the University of Maryland, MIT's Kavli Institute for Astrophysics and Space Research, and the University of California, Berkeley. The research is funded by the National Science Foundation. Observations were conducted with the Magellan Telescopes at Las Campanas Observatory in Chile.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Michigan.

Journal Reference:

Jordan Zastrow, M. S. Oey, Sylvain Veilleux, Michael McDonald, Crystal L. Martin. An ionization cone in the dwarf starburst galaxy NGC 5253. The Astrophysical Journal, 2011; 741 (1): L17 DOI: 10.1088/2041-8205/741/1/L17

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Kepler Analysis Projects One-Third of Sun-Like Stars Have an Earth-Like Planet Orbiting

Kepler Analysis Projects One-Third of Sun-Like Stars Have an Earth-Like Planet Orbiting | Popular Science@import "/files/css/1857af3413d9ad8bd2f9d3926af8ec39.css";@import "/files/css/33f6b7ecb4513ed2fe6c670880a27187.css"; home Login/Register Newsletter Subscribe RSS GadgetsComputersCamerasSmartphonesVideo GamesCarsConceptsHybridsElectric CarsScienceFuture of the EnvironmentEnergyHealthPopSci Eco TourTechnologyMilitaryAviationSpaceRobotsEngineeringDIYProjectsHacksToolsAuto DIYMore From Our Partner: Toolmonger GalleriesVideosColumnsThe GrouseSex FilesGreen Dream Innovation ChallengesHow It WorksFeatures Tweet Digg Kepler Analysis Projects One-Third of Sun-Like Stars Have an Earth-Like Planet Orbiting By Clay Dillow Posted 09.28.2011 at 2:57 pm 27 Comments
Exoplanets Around HD 10180 An artist's rendering. ESO

One of the fun things about astronomy is that we can only know so much through empirical observation, yet we can “know” so much more through enlightened, mathematical guesswork. Such is the nature of the most interesting new science paper I’ve come across on the Internet today. In it, Wesley Traub of CalTech crunches some Kepler data and makes a tantalizing mathematical prediction: one-third of sun-like stars have at least one earth-like terrestrial planet orbiting in their habitable zones.

If that turns out to be the case, that’s big news of course. The habitable zone, or the “goldilocks zone” as it’s often known (not to close to the star, not too far away), is the orbital range where it’s possible for liquid water to exist. Thus, it’s the range where life as we know it could feasibly take root.

Related ArticlesAstronomers Capture First Images of an Exoplanet Orbiting Its Star Largest Known Exoplanet DiscoveredKepler Sightings of New 'Earth-Like' Exoplanets Are Not ConfirmedTagsTechnology, Clay Dillow, exoplanets, goldilocks zone, habitable zone, kepler space telescope, SpaceThe planet-hunting Kepler observatory is designed specifically to seek out planets orbiting distant stars, and thus far its been a boon for exoplanetary science. In 136 days it has scanned some 150,000 target stars looking for the signature wobble exerted on those stars by orbiting satellites. In doing so, it has found 1,235 potential planets.

It’s from that data that Traub has extracted his conclusion. He looked particularly at the stars that are most like our sun--those classified F, G, or K. He then looked at the kinds of planets that are most often found orbiting them and at what ranges they orbit. In his analysis, he notes many interesting (and somewhat expected) things, like the fact that nearly a third of the planets Kepler has found orbit their stars in less than 42 days, putting them too close to be in the habitable zone (this is also because planets closer to their stars are easier for Kepler to see).

Larger terrestrial planets out there in the habitable zone are harder for Kepler to spot, but that doesn’t mean they’re not there. And Traub says his number crunching allows us to get a pretty good idea of how many there should be. Using some math we don’t pretend to understand, he plugged in the numbers for longer orbits--orbits in the habitable zone--into his analysis. The finding: "About one-third of FGK stars are predicted to have at least one terrestrial, habitable-zone planet."

That’s not to say they are inhabited, or that they do have liquid water, or that they even exist. But Traub’s math suggests that they should exist, at least until more data changes the equation. And for now, that spells a lot of potential goldilocks planets. Read the full paper via arXiv.

[Technology Review]

Previous Article: NASA's Falling UARS Satellite Found in Remote South PacificNext Article: Army Developing Drones That Can Recognize Your Face From a Distance 27 Comments Link to this comment eregorn8 09/28/11 at 3:39 pm

Interstellar colonization, anyone?

Link to this comment Lord Elliot the... 09/28/11 at 3:41 pm

I'm going to apply these numbers to the drake equation...
-Spouting a fountain of nonsense since 1995-

Link to this comment mp 09/28/11 at 4:07 pm

I just want them to find the mythical Planet X. And its not the recently found 10th dwarf planet Eris. Once we find planet X, we will found our 2nd earth home, YEA!

Link to this comment pheonix1012 09/28/11 at 4:30 pm

I'm not surprised. three decades ago most astronomers would agree that our existence in the universe was fairly unique. With better scientific equipment and more accurate empirical data, we find that we are not unique, but we (like the multitude of atoms in the universe) are only one of many.

I think most stars have planets around them and a good deal of them (regardless of whether they are FGK category stars) with the potential of harboring life. Thus proving the lack of random order to the universe. We are simply the byproduct of a logical design. Therefore, there must be other worlds like ours. We are seeing living proof through the discovery of terrestrial and jovian worlds.

The most random and/or rare things tend to be extremely improbable to impossible to find.

@mp

Planet X was a concept developed following the discovery of Neptune in 1846. It was born from the possibility that there was in fact another planet outside of its orbit. The search for Planet X did not start until the turn of the 20th Century leading to Pluto's discover in 1930.

Since then Planet X has been the title for any unknown planet beyond the common knowledge of the initial nine. During the previous two decades three plutonian objects were discovered and named within this solar system; two outside of Pluto's orbit in the Kuiper Belt, and one in the Prime Belt between Mars and Jupiter. In succession, there names are Eris, Haumea, and Makemake.

There are possibly several dwarf planets/plutonian objects/planetoids that rest within the Prime and the Kuiper Belt. They are probably not subjected to be named unless used as they possibly range in the thousands. Every planetary discovery following has been extrasolar (i.e. planetary discovery in a foreign star system).

Planet X is a tagline for a sci-fi character that has no clue what planet they're on (i.e. Kurt Russell portraying Col. Jack O'Neil in the 1994 film Stargate).

Link to this comment cholin3947 09/28/11 at 5:49 pm

I'd like to know how broadly "earth-like" is defined. Would Venus and Mars qualify as earth like? Would a planet like Gliese 581 d with a mass of 5.6 to 7.7 times that of Earth qualify as earth like?

Link to this comment mp 09/28/11 at 5:49 pm

pheonix1012,
Ok, ok, there you go being all factual and informative and everything.

Second, I want our science community to find the mythical planet X that is earth sister planet of which earth was seeded with human DNA. You know the science fiction planet X. I adore the Stargate series, don't you? It's real right, planet X?

I do appreciate the extra information you just provided. ;)

Link to this comment aarontco 09/28/11 at 6:28 pm

These planets are far too far away to colonize any time soon. It would be far easier to build on the moon, mars, the moons of mars, or to situate orbital colonies in LaGrange regions and in the asteroid belt(s). Of course, before we do that, there are still plenty of places on Earth too. But off-world colonies have the advantage of spreading humanity's eggs into other baskets, so we can not be so easily wiped out by a single mega-catastrophe. Orbital colonies also have great access to energy and transportation, so long as we can solve major problems, such as adequate radiation shielding, and life support system self-sufficiency.

Link to this comment mp 09/28/11 at 7:16 pm

As we clearly identify these goldilocks, perhaps we could point our satellite dishes at each of them for a while and try to hear some good chatter...

Link to this comment Toran 09/28/11 at 11:19 pm

It's sad that we proceed with presumptions and limit our search to our definition of a habital zone. Even if we want to assume that liquid water is required for life, we cannot be sure of temperatures at these distant locals. Other elements and forces we have yet to experience may be on effect.

Link to this comment inaka_rob 09/28/11 at 11:32 pm

"Ok, ok, there you go being all factual and informative and everything. "
well its is called popular science, not popular science fiction.
but yes thank you phoenix for the info. That is why I thought eris was planet X. it was only "planet X" in the fact that for a brief period they thought it was the 10th planet, hence the X, but not THE mythical planet X. thank you for the explanation.

Link to this comment inaka_rob 09/28/11 at 11:36 pm

@Toran that is a good point. Time and time agian here on Earth the definition of life has surprised us and grown (just look at the taxonmy of "life" it has grown from a 3 kingdom system to a 5 or 6 kingdom system depending on if you study in the USA or the UK. plus it was only a couple decades ago they they realized archea evolved from a totally separate track than other prokaryotes). We have found life in the most improbably places thought for thousands of years to be 100% void of life.
but I suppose they figure these goldilocks zones have a higher probability of life. So far the only life we have found is on a Goldilocks planet. Earth.

Link to this comment pheonix1012 09/29/11 at 8:47 am

@mp

Of course I like science fiction. It logically stands to motivate imaginative youth into academic interest in science.

It's just that by definition Pluto is Planet X, and Planet X is just a traditional verification of the unknown. The term is more common place for candid or satirical statements regarding unspecified worlds. For that matter their are several thousand Planet Xs.

Link to this comment boka 09/29/11 at 11:08 am

It makes more sense to develop high speed space travel to other solar systems that have earth planets than trying to build on any of the planets in our system.

Link to this comment marcoreid 09/29/11 at 11:30 am

I love science and space travel as much as the next guy, and I sure do enjoy daydreaming about what we might be able to do one day.

However... I have to question whether or not this mission's life-cycle cost of US$600 million (including funding for 3.5 years of operation) really is really justified by what we're getting out of it. Great, we get to add a bunch of planets to our long list of known exoplanets. But what does that really do for us anytime in the next few hundred years?

We take that money away from people who work very hard, many of them to make sure they have the essentials of life from day to day. Then we dump it into a project that has no hope of ever doing anything remotely useful for these people. I would think there are some serious ethical issues with that, I know there are in my mind.

That $600 million could provide enough immunizations and basic supplies in 3rd world countries to save hundreds of thousands of children from early and painful deaths. Or it could be used in the US to build thousands of homes for homeless families. Or to provide educations to tens of thousands of kids who then have the potential of becoming scientists themselves, etc.

As fun and exciting as it is to "discover" these planets that we have absolutely no means of getting to for hundreds of years, I'd rather turn more kids into scientists now so that we can more quickly develop the technology to actually visit some of these exoplanets one day.

Link to this comment Nonapod 09/29/11 at 12:05 pm

I wish they'd get a little more specific by what the term "Sun-Like". Do they generally mean all G-Type main-sequence yellow dwarf stars, or a more broader solar analogue? It's significant since something like 90% of the stars out there are cooler red or orange dwarf stars and stars like our Sun are probably more like 5-7% of the total population of stars out there.

Link to this comment JediMindset 09/29/11 at 1:39 pm

@mp
planet x is very real.
youtube.com/watch?v=8S0bj76389U
youtube.com/watch?v=xpPP9Z9LOBU

_________________
The people of the world only divide into two kinds, One sort with brains who hold no religion, The other with religion and no brain.

- Abu-al-Ala al-Marri

Link to this comment dquad 09/29/11 at 2:07 pm

I guess it is time we start constructing neutrino space ships/yawn.

Link to this comment pheonix1012 09/29/11 at 3:18 pm

@Nonapod

The star types they mention in the article are F,G, and K. You gotta read the fine print. That's how they get ya.

@boka

We already know we can survive on a carbon copy of Earth. The real trick is trying to survive in "magnificent desolation."

Besides it's easier to get to these destinations now because they are closer. We still have to develop a relativistically quick means of journeying across stellar distances before we could ever consider mounting a mission outside of the solar system.

@marcoreid

Your sentiment is noble, but we are not going to solve all of the world's problem over night. Besides, there are already organizations that exists to try and solve these problems and they get sufficient government funding which is provided in part by yours truly (the taxpayer). Just be thankful to whatever deity you may pray to that you are fortunate enough to be surrounded by luxuries such as a computer wired to the internet.

As for astronomical research, if you don't have the strategic vision to understand why we do this let me paint you a picture:

Humanity's knowledge in physics has evolved over time and it has achieved a level of mastery over the forces of the spacetime continuum. The once impossible has been proven possible and made into a reality, much as is with many instances in the history of the advancement of human civilization on Earth.

Humanity has achieved the ability to traverse interstellar distances within the blink of an eye. Following the first two successful missions to 581 Gliese d and g, a new mission is underway to HD85512 to verify the planet's potential for harboring life...

Moral of the short story: Making these discoveries now lays the foundation for exploration in the future. To cease such scientific research for lack of long term vision would prove ultimately detrimental to the future, setting us back several hundreds to thousands of years after we develop the means of instellar travel. By the time we develop these methods (especially after several hundreds of years) continued planet hunting will provide us with a library of known star systems that could range from the millions to the billions.

This would be better than the Louis and Clarke approach because space is otherwise featureless. Wondering aimlessly can trap you in a void indefinitely and send you on a trajectory clear of the galaxy without every reaching a star system. In order explore space, you gotta know where your going and the search for destinations starts here on solid ground.

Link to this comment Cookiees453 09/29/11 at 6:45 pm

In May of 2010 6.7 Billion U.S. dollars was being spent in Afghanistan a month.....1 month. This is 600 million dollars over a couple of years.....600 million is pocket change.

Link to this comment Cookiees453 09/29/11 at 6:46 pm

If the government wants to cut cost, cut the war in the middle east. (Yeah, yeah, it's not as simple as that...but whatever)

Link to this comment mp 09/29/11 at 10:37 pm

pheonix1012,
I wish to give you the award of long ranting and commentaries. First I like to say most WOA! YO DUDE, you write a lot of words and stuff! Followed how you write so much and not piss off inaka_rob. He is like such a jealous bandit for the lime light and all? Yo, friend, I am just playing. Be happy! ;)

But back to topic, I was looking at the picture in the article and I wondered why the sun is attacking the planet with these cosmic plasma balls of light and stuff. Does the sun have a beef with the planet?

I hope soon earth points our satellites towards these potentially life giving planets to hear some kind of chatter of communication. Now wouldn't that be cool to hear a new version of Star Wars from a different planet and all!

Seriously, I appreciate the extra information you provide, thanks!

Link to this comment rlb2 09/30/11 at 2:46 am

"About one-third of FGK stars are predicted to have at least one terrestrial, habitable-zone planet."

A total of 22.7 percent of all the stars in our galaxy are class FGK stars, F = 3%, G=7.6%, K=12.1%, it was suggested that 33 percent may be within the habitable-zone.
There are approximately 300 billion, 300,000,000,000, stars in our Milky Way galaxy, 150 billion in the average size Galaxy. There's approximately 200 billion galaxy's in our know universe. That would mean that there are about 22.70 billion, 22,700,000,000 planets, in our Milky Way's habitable-zone or approximately 2.27X10²¹, 2,270,000,000,000,000,000,000 planets in our universe within a class FGK stars rated habitable zone.

Ron Bennett

Link to this comment Oakspar77777 09/30/11 at 9:06 am

Of course, a "habitable zone" is a nebulous term, as things like atmospheric gas can greatly affect the surface temperature of a planet. As well, internal temperature can create a "crust" effect (as is hypothesized about Europa).

Still, 22.7 billion planets in the Milky is not going to give you a good shot at a planet where you can take off your helmet and breathe (we are very fragile in what we breathe).

As for the 600m being spent on vaccines - to what end? Save them from Malaria to insure their starvation of resource competition, or 100m for vaccines on some with 500m for food support? Of course, what about the antibiotic when their population density gives them cholera?

You cannot and will not alieviate human suffering.

Link to this comment pheonix1012 09/30/11 at 11:23 am

@mp

I'm a wealth of knowledge seeking to educate those without. I wouldn't call much of what I do ranting (though a lot of it is). I just legitimize my general platforms with details and evidence. That often takes a lot of words, but might be shorter when spoken.

Link to this comment barclay109 09/30/11 at 12:13 pm

i saw on "The Universe" that there are more than 3 suns, this is interesting, good thing I'm going to college to be an astrophysicist

Link to this comment mp 09/30/11 at 3:40 pm

I really do hope some science community finds intelligent life we earthlings can communicate in my life time!!!

.................................
pheonix1012,
If my wording sounded less complimentary, I like to rephrase myself and just say, I enjoy the additional input you provide and say thanks. ;)

Link to this comment Pasha582 10/02/11 at 2:25 pm

Marcoreid writes: We take that money away from people who work very hard, many of them to make sure they have the essentials of life from day to day.

Not really. Although the poor pay payroll taxes which CAN amount to as high a percent as hedge fund managers pay on their entire salary... The point I want to make is that science is boring, without cool projects like Kepler to stimulate the minds of budding scientists, who would want to get involved in it? What would be the point? We need research like Kepler to whet the appetites and fire the imaginations of children into pursuing careers in science. Without that, who would want to do it?

To comment, please Login. Popular TagsTechnology NASA International Space Station robots space DARPA computers UAVs drones global warming Boeing satellites All Tags All Photos All Videos Photo GalleriesRSS LinkTechnologyGallery: Inside a Knife FactoryGallery: The Biggest Satellites That Have Fallen to EarthGallery: The Soyuz Spacecraft Lands Safely in Kazakhstan+ More Photo Galleries

138 years of Popular Science at your fingertips.

Innovation Challenges Make your ideas part of the revolutionPopular Science / InnoCentive : Science Lesson Plan for Grades 6-8Award: $25,000 USDSmall Particle Dispensing TechnologyAward: $20,000 USDLearn morePowered by Innocentive

Popular Science+ For iPad

Each issue has been completely reimagined for your iPad. See our amazing new vision for magazines that goes far beyond the printed page

Download Our App

Stay up to date on the latest news of the future of science and technology from your iPhone or Android phone with full articles, images and offline viewing

Follow Us On Twitter

Featuring every article from the magazine and website, plus links from around the Web. Also see our PopSci DIY feed

October 2011: The Search for Alien Life

This month, we examine all the ways we're looking for extraterrestrial life, within our solar system and beyond.

Plus: Our annual Brilliant 10 list of young researchers, the story behind that "arsenic-based life form found" story, birth control for wildlife, and much more.

Read the issue here.

Enter here
Learn more

Popular on Popsci Most Viewed TechnologyGallery: Inside a Knife FactoryGallery: The Biggest Satellites That Have Fallen to EarthThe Incredible Shrinking Shot: Needles Get a Pain-Free MakeoverVideo: Watch BigDog, PopSci's Favorite Quadruped Bot, Romp and Grow Through the YearsToday in 3-D Printing: Musical Instruments and Instruments of WarSimulation Suggests There May Have Been a Fifth Gas Giant in Our Solar SystemGermans Manufacture Artificial Blood Vessels With a 3-D PrinterThe Military's Airship Renaissance Deflates Over Lack of Access to HeliumNetflix, Stop Floundering Around and Making Things More ComplicatedInside the Factory: How a Chef's Knife Is Made Most Commented TechnologyThe Military's Airship Renaissance Deflates Over Lack of Access to HeliumCongress Preserves James Webb Telescope For Now, But At What Cost?BullDog: A Bigger, Scarier Version of BigDog Gets Closer to the Battlefield Netflix, Stop Floundering Around and Making Things More ComplicatedThe Incredible Shrinking Shot: Needles Get a Pain-Free MakeoverChina Launches Its First Space Station Module Into OrbitKepler Analysis Projects One-Third of Sun-Like Stars Have an Earth-Like Planet OrbitingToday in 3-D Printing: Musical Instruments and Instruments of WarVideo: Watch BigDog, PopSci's Favorite Quadruped Bot, Romp and Grow Through the YearsSASSA, the Military's New Satellite Self-Defense System, is Ready to Go to Space Most Emailed TechnologyVideo: DARPA's AlphaDog Gets Up, Scrambles Over Rocks and RunsVideo: Da Vinci Surgical Robot Deftly Peels a GrapeFor the First Time, Researchers Use an Atom Interferometer to Measure Aircraft AccelerationChina Launches Its First Space Station Module Into OrbitArmy Developing Drones That Can Recognize Your Face From a DistanceGallery: Inside a Knife FactoryInside the Factory: How a Chef's Knife Is MadeKepler Analysis Projects One-Third of Sun-Like Stars Have an Earth-Like Planet OrbitingNASA's Falling UARS Satellite Found in Remote South PacificBullDog: A Bigger, Scarier Version of BigDog Gets Closer to the Battlefield Name Address 1   City State STATE Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware DC Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York N. Carolina N. Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island S. Carolina S. Dakota Tennessee Texas Utah Vermont Virginia Washington W. Virginia Wisconsin Wyoming Zip Code Email Today on PopSci.com Archive Gallery: Mail Order Kits, From the Back Pages of PopSci57197971Baffling CERN Results Show Neutrinos Moving Faster Than the Speed of Light57200972The Future of Skin56939973Dyson Hot Review: Now We're Innovating 57016974FYI: Can Anything Move Faster Than Light?56834975Archive Gallery: Offbeat Uses for Common Household Objects56998976Extremely Mobile Devices56109977Kepler Spots a Planet Orbiting Two Suns, Just Like Star Wars' Tatooine57041978Dear Nike: Here's How You Make a Self-Tying Shoe From the Future56911979The Goods: September 2011's Hottest Gadgets559319710High School Inventors 2011561269711Archive Gallery: Now You Can Watch Television in Color!568649712 Footer Menu Subscribe to the Print EditionSubscribe to the Digital EditionRenew SubscriptionCustomer ServiceSite MapAbout UsContact UsAdvertisingPrivacy PolicyTerms of UseAbuseRSS FeedsPS Showcase

 

Copyright © 2009 Popular Science

A Bonnier Corporation Company. All rights reserved. Reproduction in whole or in part without permission is prohibited.

View the original article here

Green ring fit for a superhero: Spitzer Space Telescope spies powerful light of giant 'O' stars

ScienceDaily (June 19, 2011) — This glowing emerald nebula seen by NASA's Spitzer Space Telescope is reminiscent of the glowing ring wielded by the superhero Green Lantern. In the comic books, the diminutive Guardians of the Planet "Oa" forged his power ring, but astronomers believe rings like this are actually sculpted by the powerful light of giant "O" stars. O stars are the most massive type of star known to exist.

Named RCW 120 by astronomers, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius. The green ring of dust is actually glowing in infrared colors that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors. At the center of this ring are a couple of giant stars whose intense ultraviolet light carved out the bubble, though they blend in with the other stars when viewed in infrared.

Rings like this are so common in Spitzer's observations that astronomers have even enlisted the help of the public to help find and catalog them all. Anyone interested in joining the search as a citizen scientist can visit "The Milky Way Project," part of the "Zooniverse" of public astronomy projects, at http://www.milkywayproject.org/ .

The flat plane of our galaxy is located toward the bottom of the picture, and the ring is slightly above the plane. The green haze seen at the bottom of the image is the diffuse glow of dust from the galactic plane.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA's Jet Propulsion Laboratory.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Number of stories in archives: 104,440
Post this page to your favorite social bookmarking site:Include this item in your blog or web site:Cite this article in your essay, paper, or report:Email this page's link to a friend or colleague: document.write(unescape("%3Cscript src='" + (document.location.protocol == "https:" ? "https://sb" : "http://b") + ".scorecardresearch.com/beacon.js' %3E%3C/script%3E")); COMSCORE.beacon({ c1:2, c2:1000004, c3:"", c4:"", c5:"", c6:"", c15:"" });

View the original article here

Green ring fit for a superhero: Spitzer Space Telescope spies powerful light of giant 'O' stars

ScienceDaily (June 19, 2011) — This glowing emerald nebula seen by NASA's Spitzer Space Telescope is reminiscent of the glowing ring wielded by the superhero Green Lantern. In the comic books, the diminutive Guardians of the Planet "Oa" forged his power ring, but astronomers believe rings like this are actually sculpted by the powerful light of giant "O" stars. O stars are the most massive type of star known to exist.

Named RCW 120 by astronomers, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius. The green ring of dust is actually glowing in infrared colors that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors. At the center of this ring are a couple of giant stars whose intense ultraviolet light carved out the bubble, though they blend in with the other stars when viewed in infrared.

Rings like this are so common in Spitzer's observations that astronomers have even enlisted the help of the public to help find and catalog them all. Anyone interested in joining the search as a citizen scientist can visit "The Milky Way Project," part of the "Zooniverse" of public astronomy projects, at http://www.milkywayproject.org/ .

The flat plane of our galaxy is located toward the bottom of the picture, and the ring is slightly above the plane. The green haze seen at the bottom of the image is the diffuse glow of dust from the galactic plane.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA's Jet Propulsion Laboratory.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Free-floating planets may be more common than stars

ScienceDaily (May 18, 2011) — Astronomers, including a NASA-funded team member, have discovered a new class of Jupiter-sized planets floating alone in the dark of space, away from the light of a star. The team believes these lone worlds were probably ejected from developing planetary systems.

The discovery is based on a joint Japan-New Zealand survey that scanned the center of the Milky Way galaxy during 2006 and 2007, revealing evidence for up to 10 free-floating planets roughly the mass of Jupiter. The isolated orbs, also known as orphan planets, are difficult to spot, and had gone undetected until now. The newfound planets are located at an average approximate distance of 10,000 to 20,000 light-years from Earth.

"Although free-floating planets have been predicted, they finally have been detected, holding major implications for planetary formation and evolution models," said Mario Perez, exoplanet program scientist at NASA Headquarters in Washington.

The discovery indicates there are many more free-floating Jupiter-mass planets that can't be seen. The team estimates there are about twice as many of them as stars. In addition, these worlds are thought to be at least as common as planets that orbit stars. This would add up to hundreds of billions of lone planets in our Milky Way galaxy alone.

"Our survey is like a population census," said David Bennett, a NASA and National Science Foundation-funded co-author of the study from the University of Notre Dame in South Bend, Ind. "We sampled a portion of the galaxy, and based on these data, can estimate overall numbers in the galaxy."

The study, led by Takahiro Sumi from Osaka University in Japan, appears in the May 19 issue of the journal Nature.

The survey is not sensitive to planets smaller than Jupiter and Saturn, but theories suggest lower-mass planets like Earth should be ejected from their stars more often. As a result, they are thought to be more common than free-floating Jupiters.

Previous observations spotted a handful of free-floating, planet-like objects within star-forming clusters, with masses three times that of Jupiter. But scientists suspect the gaseous bodies form more like stars than planets. These small, dim orbs, called brown dwarfs, grow from collapsing balls of gas and dust, but lack the mass to ignite their nuclear fuel and shine with starlight. It is thought the smallest brown dwarfs are approximately the size of large planets.

On the other hand, it is likely that some planets are ejected from their early, turbulent solar systems, due to close gravitational encounters with other planets or stars. Without a star to circle, these planets would move through the galaxy as our sun and other stars do, in stable orbits around the galaxy's center. The discovery of 10 free-floating Jupiters supports the ejection scenario, though it's possible both mechanisms are at play.

"If free-floating planets formed like stars, then we would have expected to see only one or two of them in our survey instead of 10," Bennett said. "Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth."

The observations cannot rule out the possibility that some of these planets may have very distant orbits around stars, but other research indicates Jupiter-mass planets in such distant orbits are rare.

The survey, the Microlensing Observations in Astrophysics (MOA), is named in part after a giant wingless, extinct bird family from New Zealand called the moa. A 5.9-foot (1.8-meter) telescope at Mount John University Observatory in New Zealand is used to regularly scan the copious stars at the center of our galaxy for gravitational microlensing events. These occur when something, such as a star or planet, passes in front of another, more distant star. The passing body's gravity warps the light of the background star, causing it to magnify and brighten. Heftier passing bodies, like massive stars, will warp the light of the background star to a greater extent, resulting in brightening events that can last weeks. Small planet-size bodies will cause less of a distortion, and brighten a star for only a few days or less.

A second microlensing survey group, the Optical Gravitational Lensing Experiment (OGLE), contributed to this discovery using a 4.2-foot (1.3 meter) telescope in Chile. The OGLE group also observed many of the same events, and their observations independently confirmed the analysis of the MOA group.

NASA's Jet Propulsion Laboratory, Pasadena,Calif., manages NASA's Exoplanet Exploration program office. JPL is a division of the California Institute of Technology in Pasadena.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Jet Propulsion Laboratory.

Journal Reference:

T. Sumi, K. Kamiya, D. P. Bennett, I. A. Bond, F. Abe, C. S. Botzler, A. Fukui, K. Furusawa, J. B. Hearnshaw, Y. Itow, P. M. Kilmartin, A. Korpela, W. Lin, C. H. Ling, K. Masuda, Y. Matsubara, N. Miyake, M. Motomura, Y. Muraki, M. Nagaya, S. Nakamura, K. Ohnishi, T. Okumura, Y. C. Perrott, N. Rattenbury, To. Saito, T. Sako, D. J. Sullivan, W. L. Sweatman, P. J. Tristram, P. C. M. Yock, A. Udalski, M. K. Szymanski, M. Kubiak, G. Pietrzynski, R. Poleski, I. Soszynski, L. Wyrzykowski, K. Ulaczyk. Unbound or distant planetary mass population detected by gravitational microlensing. Nature, 2011; 473 (7347): 349 DOI: 10.1038/nature10092

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Feuding helium dwarf stars exposed by eclipse

ScienceDaily (May 24, 2011) — Researchers at the University of Warwick have found a unique feuding double white dwarf star system where each star appears to have been stripped down to just its helium.

Astronomers know of just over 50 close double white dwarfs, but this was only the second ever eclipsing close white dwarf pair to be found. The University of Warwick astronomers Steven Parsons and Professor Tom Marsh were able to use the fact that the stars eclipse each other when seen from Earth to make particularly detailed observations of the system.

These observations revealed that uniquely both the white dwarf stars in this pairing are composed largely of helium. Most white dwarfs tend to have largely inert cores of carbon and oxygen that have formed over the star's long life when it has used up most of its hydrogen and helium. Helium white dwarfs are a sure sign that the star has undergone some extreme mass loss at some point. To find two such helium white dwarfs stars is a clear sign to astronomers that both stars have had an exotic and mutually destructive past.

What was originally the most massive star of the pair had once actually began to expand to become a red giant but its outer hydrogen envelope was ripped off by its companion. This meant the star never got an opportunity to start fusing its helium and it was left as a helium white dwarf. When the companion star then began expanded it also had its expanding layer torn off by the first star -- but as the first star was already reduced to a white dwarf it could not use that new material. That hydrogen was therefore simply lost to the star system leaving behind helium white dwarfs.

In just over 1 billion years, the two stars feud will end as they will spiral together and merge, finally igniting each other's helium to become an object known as a hot subdwarf which should last for 100 million years.

The University of Warwick researchers found this star system CSS 41177 (which is over 351 parsecs , or 1140 light years, away -- in the constellation Leo) using a combination of data from the robotic 2m Liverpool Telescope in the Canary Islands and the 8m Gemini Telescope on Hawaii.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Warwick.

Journal Reference:

S. G. Parsons, T. R. Marsh, B. T. Gänsicke, A. J. Drake, D. Koester. A deeply eclipsing detached double helium white dwarf binary. Astrophysical Journal Letters, 2011; (accepted) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

How to learn a star's true age

ScienceDaily (May 24, 2011) — For many movie stars, their age is a well-kept secret. In space, the same is true of the actual stars. Like our Sun, most stars look almost the same for most of their lives. So how can we tell if a star is one billion or 10 billion years old? Astronomers may have found a solution -- measuring the star's spin.

"A star's rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age," says astronomer Soren Meibom of the Harvard-Smithsonian Center for Astrophysics.

Meibom presented his findings May 24, 2011 in a press conference at the 218th meeting of the American Astronomical Society.

Knowing a star's age is important for many astronomical studies and in particular for planet hunters. With the bountiful harvest from NASA's Kepler spacecraft (launched in 2009) adding to previous discoveries, astronomers have found nearly 2,000 planets orbiting distant stars. Now, they want to use this new zoo of planets to understand how planetary systems form and evolve and why they are so different from each other.

"Ultimately, we need to know the ages of the stars and their planets to assess whether alien life might have evolved on these distant worlds," says Meibom. "The older the planet, the more time life has had to get started. Since stars and planets form together at the same time, if we know a star's age, we know the age of its planets too."

Learning a star's age is relatively easy when it's in a cluster of hundreds of stars that all formed at the same time. Astronomers have known for decades that if they plot the colors and brightnesses of the stars in a cluster, the pattern they see can be used to tell the cluster's age. But this technique only works on clusters. For stars not in clusters (including all stars known to have planets), determining the age is much more difficult.

Using the unique capabilities of the Kepler space telescope, Meibom and his collaborators measured the rotation rates for stars in a 1-billion-year-old cluster called NGC 6811. This new work nearly doubles the age covered by previous studies of younger clusters. It also significantly adds to our knowledge of how a star's spin rate and age are related.

If a relationship between stellar rotation and age can be established by studying stars in clusters, then measuring the rotation period of any star can be used to derive its age -- a technique called gyrochronology (pronounced ji-ro-kron-o-lo-gee). For gyrochronology to work, astronomers first must calibrate their new "clock."

They begin with stars in clusters with known ages. By measuring the spins of cluster stars, they can learn what spin rate to expect for that age. Measuring the rotation of stars in clusters with different ages tells them exactly how spin and age are related. Then by extension, they can measure the spin of a single isolated star and calculate its age.

To measure a star's spin, astronomers look for changes in its brightness caused by dark spots on its surface -- the stellar equivalent of sunspots. Any time a spot crosses the star's face, it dims slightly. Once the spot rotates out of view, the star's light brightens again. By watching how long it takes for a spot to rotate into view, across the star and out of view again, we learn how fast the star is spinning.

The changes in a star's brightness due to spots are very small, typically a few percent or less, and become smaller the older the star. Therefore, the rotation periods of stars older than about half a billion years can't be measured from the ground where Earth's atmosphere interferes. Fortunately, this is not a problem for the Kepler spacecraft. Kepler was designed specifically to measure stellar brightnesses very precisely in order to detect planets (which block a star's light ever so slightly if they cross the star's face from our point of view).

To extend the age-rotation relationship to NGC 6811, Meibom and his colleagues faced a herculean task. They spent four years painstakingly sorting out stars in the cluster from unrelated stars that just happened to be seen in the same direction. This preparatory work was done using a specially designed instrument (Hectochelle) mounted on the MMT telescope on Mt. Hopkins in southern Arizona. Hectochelle can observe 240 stars at the same time, allowing them to observe nearly 7000 stars over four years. Once they knew which stars were the real cluster stars, they used Kepler data to determine how fast those stars were spinning.

They found rotation periods ranging from 1 to 11 days (with hotter, more massive stars spinning faster), compared to the 30-day spin rate of our Sun. More importantly, they found a strong relationship between stellar mass and rotation rate, with little scatter. This result confirms that gyrochronology is a promising new method to learn the ages of isolated stars.

The team now plans to study other, older star clusters to continue calibrating their stellar "clocks." Those measurements will be more challenging because older stars spin slower and have fewer and smaller spots, meaning that the brightness changes will be even smaller and more drawn out. Nevertheless, they feel up to the challenge.

"This work is a leap in our understanding of how stars like our Sun work. It also may have an important impact on our understanding of planets found outside our solar system," said Meibom.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Harvard-Smithsonian Center for Astrophysics.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Feuding helium dwarf stars exposed by eclipse

ScienceDaily (May 24, 2011) — Researchers at the University of Warwick have found a unique feuding double white dwarf star system where each star appears to have been stripped down to just its helium.

Astronomers know of just over 50 close double white dwarfs, but this was only the second ever eclipsing close white dwarf pair to be found. The University of Warwick astronomers Steven Parsons and Professor Tom Marsh were able to use the fact that the stars eclipse each other when seen from Earth to make particularly detailed observations of the system.

These observations revealed that uniquely both the white dwarf stars in this pairing are composed largely of helium. Most white dwarfs tend to have largely inert cores of carbon and oxygen that have formed over the star's long life when it has used up most of its hydrogen and helium. Helium white dwarfs are a sure sign that the star has undergone some extreme mass loss at some point. To find two such helium white dwarfs stars is a clear sign to astronomers that both stars have had an exotic and mutually destructive past.

What was originally the most massive star of the pair had once actually began to expand to become a red giant but its outer hydrogen envelope was ripped off by its companion. This meant the star never got an opportunity to start fusing its helium and it was left as a helium white dwarf. When the companion star then began expanded it also had its expanding layer torn off by the first star -- but as the first star was already reduced to a white dwarf it could not use that new material. That hydrogen was therefore simply lost to the star system leaving behind helium white dwarfs.

In just over 1 billion years, the two stars feud will end as they will spiral together and merge, finally igniting each other's helium to become an object known as a hot subdwarf which should last for 100 million years.

The University of Warwick researchers found this star system CSS 41177 (which is over 351 parsecs , or 1140 light years, away -- in the constellation Leo) using a combination of data from the robotic 2m Liverpool Telescope in the Canary Islands and the 8m Gemini Telescope on Hawaii.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Warwick.

Journal Reference:

S. G. Parsons, T. R. Marsh, B. T. Gänsicke, A. J. Drake, D. Koester. A deeply eclipsing detached double helium white dwarf binary. Astrophysical Journal Letters, 2011; (accepted) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

How 'hot Jupiters' got so close to their stars: Extrasolar planet research sheds light on our solar system

ScienceDaily (May 12, 2011) — More than 500 extrasolar planets -- planets that orbit stars other than the sun -- have been discovered since 1995. But only in the last few years have astronomers observed that in some of these systems the star is spinning one way and the planet, a "hot Jupiter," is orbiting the star in the opposite direction.

"That's really weird, and it's even weirder because the planet is so close to the star," said Frederic A. Rasio, a theoretical astrophysicist at Northwestern University. "How can one be spinning one way and the other orbiting exactly the other way? It's crazy. It so obviously violates our most basic picture of planet and star formation."

Figuring out how these huge planets got so close to their stars led Rasio and his research team to also explain their flipped orbits. Using large-scale computer simulations, they are the first to model how a hot Jupiter's orbit can flip and go in the direction opposite to the star's spin. Gravitational perturbations by a much more distant planet result in the hot Jupiter having both a "wrong way" and a very close orbit. (A hot Jupiter is a huge Jupiter-like planet in very close proximity to the central star.)

"Once you get more than one planet, the planets perturb each other gravitationally," Rasio said. "This becomes interesting because that means whatever orbit they were formed on isn't necessarily the orbit they will stay on forever. These mutual perturbations can change the orbits, as we see in these extrasolar systems."

Details of the study will be published May 12 by the journal Nature.

In explaining the peculiar configuration of an extrasolar system, the researchers also have added to our general understanding of planetary system formation and evolution and reflected on what their findings mean for the solar system.

"We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems," Rasio said. "That makes us the odd ball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place."

Rasio, a professor of physics and astronomy in Northwestern's Weinberg College of Arts and Sciences is the senior author of the paper. The first author is Smadar Naoz, a postdoctoral fellow at Northwestern and a Gruber Fellow.

The physics the research team used to solve the problem is basically orbital mechanics, Rasio said, the same kind of physics NASA uses to send satellites around the solar system.

"It was a beautiful problem," said Naoz, "because the answer was there for us for so long. It's the same physics, but no one noticed it could explain hot Jupiters and flipped orbits."

"Doing the calculations was not obvious or easy," Rasio said, "Some of the approximations used by others in the past were really not quite right. We were doing it right for the first time in 50 years, thanks in large part to the persistence of Smadar."

"It takes a smart, young person who first can do the calculations on paper and develop a full mathematical model and then turn it into a computer program that solves the equations," Rasio added. "This is the only way we can produce real numbers to compare to the actual measurements taken by astronomers."

In their model, the researchers assume a star similar to the sun, and a system with two planets. The inner planet is a gas giant similar to Jupiter, and initially it is far from the star, where Jupiter-type planets are thought to form. The outer planet is also fairly large and is farther from the star than the first planet. It interacts with the inner planet, perturbing it and shaking up the system.

The effects on the inner planet are weak but build up over a very long period of time, resulting in two significant changes in the system: the inner gas giant orbits very close to the star and its orbit is in the opposite direction of the central star's spin. The changes occur, according to the model, because the two orbits are exchanging angular momentum, and the inner one loses energy via strong tides.

The gravitational coupling between the two planets causes the inner planet to go into an eccentric, needle-shaped orbit. It has to lose a lot of angular momentum, which it does by dumping it onto the outer planet. The inner planet's orbit gradually shrinks because energy is dissipated through tides, pulling in close to the star and producing a hot Jupiter. In the process, the orbit of the planet can flip.

Only about a quarter of astronomers' observations of these hot Jupiter systems show flipped orbits. The Northwestern model needs to be able to produce both flipped and non-flipped orbits, and it does, Rasio said.

The title of the paper is "Hot Jupiters From Secular Planet-Planet Interactions." In addition to Rasio and Naoz, other authors of the paper are Will M. Farr, a CIERA postdoctoral fellow; Yoram Lithwick, an assistant professor of physics and astronomy; and Jean Teyssandier, a visiting pre-doctoral fellow, all from Northwestern.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Smadar Naoz, Will M. Farr, Yoram Lithwick, Frederic A. Rasio, Jean Teyssandier. Hot Jupiters from secular planet–planet interactions. Nature, 2011; 473 (7346): 187 DOI: 10.1038/nature10076

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Free-floating planets may be more common than stars

ScienceDaily (May 18, 2011) — Astronomers, including a NASA-funded team member, have discovered a new class of Jupiter-sized planets floating alone in the dark of space, away from the light of a star. The team believes these lone worlds were probably ejected from developing planetary systems.

The discovery is based on a joint Japan-New Zealand survey that scanned the center of the Milky Way galaxy during 2006 and 2007, revealing evidence for up to 10 free-floating planets roughly the mass of Jupiter. The isolated orbs, also known as orphan planets, are difficult to spot, and had gone undetected until now. The newfound planets are located at an average approximate distance of 10,000 to 20,000 light-years from Earth.

"Although free-floating planets have been predicted, they finally have been detected, holding major implications for planetary formation and evolution models," said Mario Perez, exoplanet program scientist at NASA Headquarters in Washington.

The discovery indicates there are many more free-floating Jupiter-mass planets that can't be seen. The team estimates there are about twice as many of them as stars. In addition, these worlds are thought to be at least as common as planets that orbit stars. This would add up to hundreds of billions of lone planets in our Milky Way galaxy alone.

"Our survey is like a population census," said David Bennett, a NASA and National Science Foundation-funded co-author of the study from the University of Notre Dame in South Bend, Ind. "We sampled a portion of the galaxy, and based on these data, can estimate overall numbers in the galaxy."

The study, led by Takahiro Sumi from Osaka University in Japan, appears in the May 19 issue of the journal Nature.

The survey is not sensitive to planets smaller than Jupiter and Saturn, but theories suggest lower-mass planets like Earth should be ejected from their stars more often. As a result, they are thought to be more common than free-floating Jupiters.

Previous observations spotted a handful of free-floating, planet-like objects within star-forming clusters, with masses three times that of Jupiter. But scientists suspect the gaseous bodies form more like stars than planets. These small, dim orbs, called brown dwarfs, grow from collapsing balls of gas and dust, but lack the mass to ignite their nuclear fuel and shine with starlight. It is thought the smallest brown dwarfs are approximately the size of large planets.

On the other hand, it is likely that some planets are ejected from their early, turbulent solar systems, due to close gravitational encounters with other planets or stars. Without a star to circle, these planets would move through the galaxy as our sun and other stars do, in stable orbits around the galaxy's center. The discovery of 10 free-floating Jupiters supports the ejection scenario, though it's possible both mechanisms are at play.

"If free-floating planets formed like stars, then we would have expected to see only one or two of them in our survey instead of 10," Bennett said. "Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth."

The observations cannot rule out the possibility that some of these planets may have very distant orbits around stars, but other research indicates Jupiter-mass planets in such distant orbits are rare.

The survey, the Microlensing Observations in Astrophysics (MOA), is named in part after a giant wingless, extinct bird family from New Zealand called the moa. A 5.9-foot (1.8-meter) telescope at Mount John University Observatory in New Zealand is used to regularly scan the copious stars at the center of our galaxy for gravitational microlensing events. These occur when something, such as a star or planet, passes in front of another, more distant star. The passing body's gravity warps the light of the background star, causing it to magnify and brighten. Heftier passing bodies, like massive stars, will warp the light of the background star to a greater extent, resulting in brightening events that can last weeks. Small planet-size bodies will cause less of a distortion, and brighten a star for only a few days or less.

A second microlensing survey group, the Optical Gravitational Lensing Experiment (OGLE), contributed to this discovery using a 4.2-foot (1.3 meter) telescope in Chile. The OGLE group also observed many of the same events, and their observations independently confirmed the analysis of the MOA group.

NASA's Jet Propulsion Laboratory, Pasadena,Calif., manages NASA's Exoplanet Exploration program office. JPL is a division of the California Institute of Technology in Pasadena.

More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Jet Propulsion Laboratory.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here