Astronomers Solve Mystery of Vanishing Electrons in Earth's Outer Radiation Belt

UCLA researchers have explained the puzzling disappearing act of energetic electrons in Earth's outer radiation belt, using data collected from a fleet of orbiting spacecraft. (Credit: NASA Goddard Space Flight Center / Image by Reto Stöckli /Enhancements by Robert Simmon)

UCLA researchers have explained the puzzling disappearing act of energetic electrons in Earth's outer radiation belt, using data collected from a fleet of orbiting spacecraft.

In a paper published Jan. 29 in the advance online edition of the journalNature Physics, the team shows that the missing electrons are swept away from the planet by a tide of solar wind particles during periods of heightened solar activity.

"This is an important milestone in understanding Earth's space environment," said lead study author Drew Turner, an assistant researcher in the UCLA Department of Earth and Space Sciences and a member of UCLA's Institute for Geophysics and Planetary Physics (IGPP). "We are one step closer towards understanding and predicting space weather phenomena."

During powerful solar events such as coronal mass ejections, parts of the magnetized outer layers of sun's atmosphere crash onto Earth's magnetic field, triggering geomagnetic storms capable of damaging the electronics of orbiting spacecraft. These cosmic squalls have a peculiar effect on Earth's outer radiation belt, a doughnut-shaped region of space filled with electrons so energetic that they move at nearly the speed of light.

"During the onset of a geomagnetic storm, nearly all the electrons trapped within the radiation belt vanish, only to come back with a vengeance a few hours later," said Vassilis Angelopoulos, a UCLA professor of Earth and space sciences and IGPP researcher.

The missing electrons surprised scientists when the trend was first measured in the 1960s by instruments onboard the earliest spacecraft sent into orbit, said study co-author Yuri Shprits, a research geophysicist with the IGPP and the departments of Earth and space sciences, and atmospheric and oceanic sciences.

"It's a puzzling effect," he said. "Oceans on Earth do not suddenly lose most of their water, yet radiation belts filled with electrons can be rapidly depopulated."

Even stranger, the electrons go missing during the peak of a geomagnetic storm, a time when one might expect the radiation belt to be filled with energetic particles because of the extreme bombardment by the solar wind.

Where do the electrons go? This question has remained unresolved since the early 1960s. Some believed the electrons were lost to Earth's atmosphere, while others hypothesized that the electrons were not permanently lost at all but merely temporarily drained of energy so that they appeared absent.

"Our study in 2006 suggested that electrons may be, in fact, lost to the interplanetary medium and decelerated by moving outwards," Shprits said. "However, until recently, there was no definitive proof for this theory."

To resolve the mystery, Turner and his team used data from three networks of orbiting spacecraft positioned at different distances from Earth to catch the escaping electrons in the act. The data show that while a small amount of the missing energetic electrons did fall into the atmosphere, the vast majority were pushed away from the planet, stripped away from the radiation belt by the onslaught of solar wind particles during the heightened solar activity that generated the magnetic storm itself.

A greater understanding of Earth's radiation belts is vital for protecting the satellites we rely on for global positioning, communications and weather monitoring, Turner said. Earth's outer radiation belt is a harsh radiation environment for spacecraft and astronauts; the high-energy electrons can penetrate a spacecraft's shielding and wreak havoc on its delicate electronics. Geomagnetic storms triggered when the oncoming particles smash into Earth's magnetosphere can cause partial or total spacecraft failure.

"While most satellites are designed with some level of radiation protection in mind, spacecraft engineers must rely on approximations and statistics because they lack the data needed to model and predict the behavior of high-energy electrons in the outer radiation belt," Turner said.

During the 2003 "Halloween Storm," more than 30 satellites reported malfunctions, and one was a total loss, said Angelopoulos, a co-author of the current research. As the solar maximum approaches in 2013, marking the sun's peak activity over a roughly 11-year cycle, geomagnetic storms may occur as often as several times per month.

"High-energy electrons can cut down the lifetime of a spacecraft significantly," Turner said. "Satellites that spend a prolonged period within the active radiation belt might stop functioning years early."

While a mechanized spacecraft might include multiple redundant circuits to reduce the risk of total failure during a solar event, human explorers in orbit do not have the same luxury. High-energy electrons can punch through astronauts' spacesuits and pose serious health risks, Turner said.

"As a society, we've become incredibly dependent on space-based technology," he said. "Understanding this population of energetic electrons and their extreme variations will help create more accurate models to predict the effect of geomagnetic storms on the radiation belts."

Key observational data used in this study was collected by a network of NASA spacecraft known as THEMIS (Time History of Events and Macroscale Interactions during Substorms); Angelopoulos is the principal investigator of the THEMIS mission. Additional information was obtained from two groups of weather satellites called POES (Polar Operational Environmental Satellite) and GOES (Geostationary Operational Environmental Satellite).

A new collaboration between UCLA and Russia's Moscow State University promises to paint an even clearer picture of these vanishing electrons. Slated for launch in the spring of 2012, the Lomonosov spacecraft will fly in low Earth orbit to measure highly energetic particles with unprecedented accuracy, said Shprits, the principal investigator of the project. Several key instruments for the mission are being developed and assembled at UCLA.

Earth's radiation belts were discovered in 1958 by Explorer I, the first U.S. satellite that traveled to space.

"What we are studying was the first discovery of the space age," Shprits said. "People realized that launches of spacecraft didn't only make the news, they could also make scientific discoveries that were completely unexpected."

This project received federal funding from NASA and the National Science Foundation. Other co-authors include Michael Hartinger, a UCLA graduate student in Earth and space sciences.

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The above story is reprinted from materials provided by University of California - Los Angeles. The original article was written by Kim DeRose.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. Drew L. Turner, Yuri Shprits, Michael Hartinger, Vassilis Angelopoulos. Explaining sudden losses of outer radiation belt electrons during geomagnetic storms.Nature Physics, 2012; DOI: 10.1038/nphys2185

Lab Mimics Jupiter's Trojan Asteroids Inside a Single Atom

Rice University graduate student Shuzhen Ye used an ultraviolet laser to create a Rydberg atom in order to study the orbital mechanics of electrons. (Credit: Jeff Fitlow/Rice University)

ScienceDaily  — Rice University physicists have gone to extremes to prove that Isaac Newton's classical laws of motion can apply in the atomic world: They've built an accurate model of part of the solar system inside a single atom of potassium.

In a new paper published this week in Physical Review Letters, Rice's team and collaborators at the Oak Ridge National Laboratory and the Vienna University of Technology showed they could cause an electron in an atom to orbit the nucleus in precisely the same way that Jupiter's Trojan asteroids orbit the sun.

The findings uphold a prediction made in 1920 by famed Danish physicist Niels Bohr about the relationship between the then-new science of quantum mechanics and Newton's tried-and-true laws of motion.

"Bohr predicted that quantum mechanical descriptions of the physical world would, for systems of sufficient size, match the classical descriptions provided by Newtonian mechanics," said lead researcher Barry Dunning, Rice's Sam and Helen Worden Professor of Physics and chair of the Department of Physics and Astronomy. "Bohr also described the conditions under which this correspondence could be observed. In particular, he said it should be seen in atoms with very high principal quantum numbers, which are exactly what we study in our laboratory."

Bohr was a pioneer of quantum physics. His 1913 atomic model, which is still widely invoked today, postulated a small nucleus surrounded by electrons moving in well-defined orbits and shells. The word "quantum" in quantum mechanics derives from the fact that these orbits can have only certain well-defined energies. Jumps between these orbits lead to absorption or emission of specific amounts of energy termed quanta. As an electron gains energy, its quantum number increases, and it jumps to higher orbits that circle ever farther from the nucleus.

In the new experiments, Rice graduate students Brendan Wyker and Shuzhen Ye began by using an ultraviolet laser to create a Rydberg atom. Rydberg atoms contain a highly excited electron with a very large quantum number. In the Rice experiments, potassium atoms with quantum numbers between 300 and 600 were studied.

"In such excited states, the potassium atoms become hundreds of thousands of times larger than normal and approach the size of a period at the end of a sentence," Dunning said. "Thus, they are good candidates to test Bohr's prediction."

He said comparing the classical and quantum descriptions of the electron orbits is complicated, in part because electrons exist as both particles and waves. To "locate" an electron, physicists calculate the likelihood of finding the electron at different locations at a given time. These predictions are combined to create a "wave function" that describes all the places where the electron might be found. Normally, an electron's wave function looks like a diffuse cloud that surrounds the atomic nucleus, because the electron might be found on any side of the nucleus at a given time.

Dunning and co-workers previously used a tailored sequence of electric field pulses to collapse the wave function of an electron in a Rydberg atom; this limited where it might be found to a localized, comma-shaped area called a "wave packet." This localized wave packet orbited the nucleus of the atom much like a planet orbits the sun. But the effect lasted only for a brief period.

"We wanted to see if we could develop a way to use radio frequency waves to capture this localized electron and make it orbit the nucleus indefinitely without spreading out," Ye said.

They succeeded by applying a radio frequency field that rotated around the nucleus itself. This field ensnared the localized electron and forced it to rotate in lockstep around the nucleus.

A further electric field pulse was used to measure the final result by taking a snapshot of the wave packet and destroying the delicate Rydberg atom in the process. After the experiment had been run tens of thousands of times, all the snapshots were combined to show that Bohr's prediction was correct: The classical and quantum descriptions of the orbiting electron wave packets matched. In fact, the classical description of the wave packet trapped by the rotating field parallels the classical physics that explains the behavior of Jupiter's Trojan asteroids.

Jupiter's 4,000-plus Trojan asteroids -- so called because each is named for a hero of the Trojan wars -- have the same orbit as Jupiter and are contained in comma-shaped clouds that look remarkably similar to the localized wave packets created in the Rice experiments. And just as the wave packet in the atom is trapped by the combined electric field from the nucleus and the rotating wave, the Trojans are trapped by the combined gravitational field of the sun and orbiting Jupiter.

The researchers are now working on their next experiment: They're attempting to localize two electrons and have them orbit the nucleus like two planets in different orbits.

"The level of control that we're able to achieve in these atoms would have been unthinkable just a few years ago and has potential applications in, for example, quantum computing and in controlling chemical reactions using ultrafast lasers," Dunning said.

The research was funded by the National Science Foundation, the Robert A. Welch Foundation, the Austrian Science Fund and the Department of Energy. Paper co-authors include S. Yoshida of the Vienna University of Technology; C.O. Reinhold of Oak Ridge National Laboratory and the University of Tennessee; and J. Burgdörfer of Vienna University of Technology and the University of Tennessee.

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---

Journal Reference:

1. B. Wyker, S. Ye, F. Dunning, S. Yoshida, C. Reinhold, J. Burgdörfer. Creating and Transporting Trojan Wave Packets. Physical Review Letters, 2012; 108 (4) DOI:10.1103/PhysRevLett.108.043001

Astronomers discover complex organic matter exists throughout the universe

ScienceDaily (Oct. 26, 2011) — Astronomers report in the journal Nature that organic compounds of unexpected complexity exist throughout the Universe. The results suggest that complex organic compounds are not the sole domain of life but can be made naturally by stars.

Prof. Sun Kwok and Dr. Yong Zhang of The University of Hong Kong show that an organic substance commonly found throughout the Universe contains a mixture of aromatic (ring-like) and aliphatic (chain-like) components. The compounds are so complex that their chemical structures resemble those of coal and petroleum. Since coal and oil are remnants of ancient life, this type of organic matter was thought to arise only from living organisms. The team's discovery suggests that complex organic compounds can be synthesized in space even when no life forms are present.

The researchers investigated an unsolved phenomenon: a set of infrared emissions detected in stars, interstellar space, and galaxies. These spectral signatures are known as "Unidentified Infrared Emission features." For over two decades, the most commonly accepted theory on the origin of these signatures has been that they come from simple organic molecules made of carbon and hydrogen atoms, called polycyclic aromatic hydrocarbon (PAH) molecules. From observations taken by the Infrared Space Observatory and the Spitzer Space Telescope, Kwok and Zhang showed that the astronomical spectra have features that cannot be explained by PAH molecules. Instead, the team proposes that the substances generating these infrared emissions have chemical structures that are much more complex. By analyzing spectra of star dust formed in exploding stars called novae, they show that stars are making these complex organic compounds on extremely short time scales of weeks.

Not only are stars producing this complex organic matter, they are also ejecting it into the general interstellar space, the region between stars. The work supports an earlier idea proposed by Kwok that old stars are molecular factories capable of manufacturing organic compounds. "Our work has shown that stars have no problem making complex organic compounds under near-vacuum conditions," says Kwok. "Theoretically, this is impossible, but observationally we can see it happening."

Most interestingly, this organic star dust is similar in structure to complex organic compounds found in meteorites. Since meteorites are remnants of the early Solar System, the findings raise the possibility that stars enriched the early Solar System with organic compounds. The early Earth was subjected to severe bombardments by comets and asteroids, which potentially could have carried organic star dust. Whether these delivered organic compounds played any role in the development of life on Earth remains an open question.

Prof. Sun Kwok is the Dean of Science and Chair Professor of Physics of the University of Hong Kong. He serves as Vice President of Division VI (interstellar matter) of the International Astronomical Union, and is the incoming Vice President of Commission 51 (bioastronomy) of the International Astronomical Union. He has published many books, including the recent book "Organic Matter in the Universe" (Wiley, 2011). Dr. Yong Zhang is a Research Assistant Professor at the University of Hong Kong. This work was supported by the Research Grants Council of Hong Kong.

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Journal Reference:

Sun Kwok, Yong Zhang. Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features. Nature, 2011; DOI: 10.1038/nature10542

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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.

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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.

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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

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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.

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

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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

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Astronomers find elusive planets in decade-old Hubble data

ScienceDaily (Oct. 6, 2011) — In a painstaking re-analysis of Hubble Space Telescope images from 1998, astronomers have found visual evidence for two extrasolar planets that went undetected back then.

Finding these hidden gems in the Hubble archive gives astronomers an invaluable time machine for comparing much earlier planet orbital motion data to more recent observations. It also demonstrates a novel approach for planet hunting in archival Hubble data.

Four giant planets are known to orbit the young, massive star HR 8799, which is130 light-years away. In 2007 and 2008 the first three planets were discovered in near-infrared ground-based images taken with the W.M. Keck Observatory and the Gemini North telescope by Christian Marois of the National Research Council in Canada and his team. Marois and his colleagues then uncovered a fourth innermost planet in 2010. This is the only multiple exoplanetary system for which astronomers have obtained direct snapshots.

In 2009 David Lafreniere of the University of Montreal recovered hidden exoplanet data in Hubble images of HR 8799 taken in 1998 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). He identified the position of the outermost planet known to orbit the star. This first demonstrated the power of a new data-processing technique for retrieving faint planets buried in the glow of the central star.

A new analysis of the same archival NICMOS data by Remi Soummer of the Space Telescope Science Institute in Baltimore has recovered all three of the outer planets. The fourth, innermost planet is 1.5 billion miles from the star and cannot be seen because it is on the edge of the NICMOS coronagraphic spot that blocks the light from the central star.

By finding the planets in multiple images spaced over years of time, the orbits of the planets can be tracked. Knowing the orbits is critical to understanding the behavior of multiple-planet systems because massive planets can perturb each other's orbits. "From the Hubble images we can determine the shape of their orbits, which brings insight into the system stability, planet masses and eccentricities, and also the inclination of the system," says Soummer.

These results are to be published in the Astrophysical Journal.

The three outer gas-giant planets have approximately 100-, 200-, and 400-year orbits. This means that astronomers need to wait a very long time to see how the planets move along their paths. The added time span from the Hubble data helps enormously. "The archive got us 10 years of science right now," he says. "Without this data we would have had to wait another decade. It's 10 years of science for free."

Nevertheless, the slowest-moving, outermost planet has barely changed position in 10 years. "But if we go to the next inner planet we see a little bit of an orbit, and the third inner planet we actually see a lot of motion," says Soummer.

The planets weren't found in 1998 when the Hubble observations were first taken because the methods used to detect them were not available at that time. When astronomers subtracted the light from the central star to look for the residual glow of planets, the residual light scatter was still overwhelming the faint planets.

Lafreniere developed a way to improve this type of analysis by using a library of reference stars to more precisely remove the "fingerprint" glow of the central star. Soummer's team took Lafreniere's method a step further and used 466 images of reference stars taken from a library containing over 10 years of NICMOS observations assembled by Glenn Schneider of the University of Arizona.

Soummer's team further increased contrast and minimized residual starlight. They completely removed the diffraction spikes, which are artifacts common to telescope imaging systems. This allowed them to see two of the faint inner planets in the Hubble data. The planets recovered in the NICMOS data are about 1/100,000th the brightness of the parent star when viewed in near-infrared light.

Soummer next plans to analyze approximately 400 other stars in the NICMOS archive with the same technique, improving image quality by a factor of 10 over the imaging methods used when the data were obtained.

Soummer's work demonstrates the power of the Hubble Space Telescope data archive, which harbors images and spectral information from over twenty years of Hubble observations. Astronomers tap into this library to complement new observations with a wealth of invaluable data already gathered, yielding much more discovery potential than new observations alone.

From the NICMOS archive data Soummer's team will assemble a list of planetary candidates to be confirmed by ground-based telescopes. If new planets are discovered they will once again have several years' worth of orbital motion to measure.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

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Astronomers find elusive planets in decade-old Hubble data

ScienceDaily (Oct. 6, 2011) — In a painstaking re-analysis of Hubble Space Telescope images from 1998, astronomers have found visual evidence for two extrasolar planets that went undetected back then.

Finding these hidden gems in the Hubble archive gives astronomers an invaluable time machine for comparing much earlier planet orbital motion data to more recent observations. It also demonstrates a novel approach for planet hunting in archival Hubble data.

Four giant planets are known to orbit the young, massive star HR 8799, which is130 light-years away. In 2007 and 2008 the first three planets were discovered in near-infrared ground-based images taken with the W.M. Keck Observatory and the Gemini North telescope by Christian Marois of the National Research Council in Canada and his team. Marois and his colleagues then uncovered a fourth innermost planet in 2010. This is the only multiple exoplanetary system for which astronomers have obtained direct snapshots.

In 2009 David Lafreniere of the University of Montreal recovered hidden exoplanet data in Hubble images of HR 8799 taken in 1998 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). He identified the position of the outermost planet known to orbit the star. This first demonstrated the power of a new data-processing technique for retrieving faint planets buried in the glow of the central star.

A new analysis of the same archival NICMOS data by Remi Soummer of the Space Telescope Science Institute in Baltimore has recovered all three of the outer planets. The fourth, innermost planet is 1.5 billion miles from the star and cannot be seen because it is on the edge of the NICMOS coronagraphic spot that blocks the light from the central star.

By finding the planets in multiple images spaced over years of time, the orbits of the planets can be tracked. Knowing the orbits is critical to understanding the behavior of multiple-planet systems because massive planets can perturb each other's orbits. "From the Hubble images we can determine the shape of their orbits, which brings insight into the system stability, planet masses and eccentricities, and also the inclination of the system," says Soummer.

These results are to be published in the Astrophysical Journal.

The three outer gas-giant planets have approximately 100-, 200-, and 400-year orbits. This means that astronomers need to wait a very long time to see how the planets move along their paths. The added time span from the Hubble data helps enormously. "The archive got us 10 years of science right now," he says. "Without this data we would have had to wait another decade. It's 10 years of science for free."

Nevertheless, the slowest-moving, outermost planet has barely changed position in 10 years. "But if we go to the next inner planet we see a little bit of an orbit, and the third inner planet we actually see a lot of motion," says Soummer.

The planets weren't found in 1998 when the Hubble observations were first taken because the methods used to detect them were not available at that time. When astronomers subtracted the light from the central star to look for the residual glow of planets, the residual light scatter was still overwhelming the faint planets.

Lafreniere developed a way to improve this type of analysis by using a library of reference stars to more precisely remove the "fingerprint" glow of the central star. Soummer's team took Lafreniere's method a step further and used 466 images of reference stars taken from a library containing over 10 years of NICMOS observations assembled by Glenn Schneider of the University of Arizona.

Soummer's team further increased contrast and minimized residual starlight. They completely removed the diffraction spikes, which are artifacts common to telescope imaging systems. This allowed them to see two of the faint inner planets in the Hubble data. The planets recovered in the NICMOS data are about 1/100,000th the brightness of the parent star when viewed in near-infrared light.

Soummer next plans to analyze approximately 400 other stars in the NICMOS archive with the same technique, improving image quality by a factor of 10 over the imaging methods used when the data were obtained.

Soummer's work demonstrates the power of the Hubble Space Telescope data archive, which harbors images and spectral information from over twenty years of Hubble observations. Astronomers tap into this library to complement new observations with a wealth of invaluable data already gathered, yielding much more discovery potential than new observations alone.

From the NICMOS archive data Soummer's team will assemble a list of planetary candidates to be confirmed by ground-based telescopes. If new planets are discovered they will once again have several years' worth of orbital motion to measure.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

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Giant star expels multiple dust shells, astronomers find

ScienceDaily (Sep. 27, 2011) — An international team led by KU Leuven astronomer Leen Decin discovered not less than a dozen cold dust arcs around the giant star CW Leo. The team used the sensitive PACS instrument on board the Herschel Space Observatory to detect for the first time arcs of dust far away from the star. CW Leo has expelled these shells of dust in different epochs in its life. The faintest shell we can see now was, according to the team, expelled about 16,000 years ago. In the mean time it has drifted away from the star over more than 7,000 billion kilometers.

Episodes

"Until recently, the environment of giant stars seemed homogeneous, but more and more observations indicate that this is not true," says Leen Decin. "These new Herschel images confirm that in a stunning way. We have detected a dozen arcs, puffed out by the star in the course of its life. The faintest shell we found is already at a distance of 7,000 billion kilometers from the star."

The different shells were ejected by the star with intervals of 500 to 1,700 years. The astronomers in the team believe such shells, even fainter, are also present further out, up to the violent bow shock where the expelled material of the star collides with the interstellar medium. The oldest shells have probably disappeared in the bow shock already.

Our own Sun too will turn into a red giant star, about five billion years from now, when it will inflate and condensate dust in the outer, cooling layers of its atmosphere. The episodes in CW Leo's history help astronomers understand the future of our own Sun.

Cold

Since the different shells have been travelling far away from the star by now, they are also very cold, about -248°C. The PACS instrument onboard the Herschel Space Telescope was especially designed to make images of the far-infrared light emitted by dust that cold. Thanks to the Belgian participation in the building of the PACS instrument, the team got priority access to the space telescope. Christoffel Waelkens, Co-principal investigator of the PACS instrument consortium is proud of yet another discovery by Herschel: "We had a lot of ideas for science with Herschel, but we also hoped that Herschel would surprise us with unexpected results. It has been a continuous delight since the first observations: at every opportunity nature proves to have more imagination than we have, but still presents us the phenomena so that we can understand them."

Digging in the data

Making the rings visible in the Herschel images was not trivial. Pierre Royer, instrument expert in the PACS team of the Institute of Astronomy at KU Leuven, clarifies: "The work of constantly refining the instrumental calibration and improving the data-analysis techniques really becomes rewarding when it comes to push the instrument to its limits, allowing for cutting-edge science." Also after the Herschel Launch in 2009 the PACS instrument team, including 7 scientists and engineers at KU Leuven, continued to refine the initial calibration and data analysis software.

Publication

The team published the results in the October 2011 issue of the journal Astronomy & Astrophysics.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Katholieke Universiteit Leuven.

Journal Reference:

L. Decin, P. Royer, N. L. J. Cox, B. Vandenbussche, R. Ottensamer, J. A. D. L. Blommaert, M. A. T. Groenewegen, M. J. Barlow, T. Lim, F. Kerschbaum, T. Posch, C. Waelkens. Discovery of multiple dust shells beyond 1?arcmin in the circumstellar envelope of IRC +10216 usingHerschel/PACS. Astronomy & Astrophysics, 2011; 534: A1 DOI: 10.1051/0004-6361/201117360

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Astronomers reveal supernova factory

ScienceDaily (Oct. 2, 2011) — A team led by astronomers at Chalmers and Onsala Space Observatory has detected seven previously unknown supernovae in a galaxy 250 million light years away. Never before have so many supernovae been discovered at the same time in the same galaxy. The discovery proves what astronomers have long believed: that the galaxies which are the universe's most efficient star-factories are also supernova factories.

The astronomers used a worldwide network of radio telescopes in five countries, including Sweden, to be able to create extremely sharp images of the galaxy Arp 220. The scientists observed around 40 radio sources in the center of the galaxy Arp 220. These radio sources are hidden behind thick layers of dust and gas and invisible in ordinary telescopes. To discover the nature of these radio sources, they made measurements at different radio wavelengths and watched how they changed over several years.

"With all the data in place, we can now be certain that all seven of these sources are supernovae: stars that exploded in the last 60 years," says Fabien Batejat, main author of the article about the discovery.

So many supernovae have never before been detected in the same galaxy. The number is nevertheless consistent with how fast stars are forming in Arp 220.

"In Arp 220, we see far more supernovae than in our galaxy. We estimate that a star explodes in Arp 220 once every quarter. In the Milky Way, there is only one supernova per century," says Rodrigo Parra, astronomer at the European Southern Observatory in Chile and member of the team.

John Conway is professor of observational radio astronomy at Chalmers and deputy director of Onsala Space Observatory.

"Arp 220 is well-known as a place where star formation is very efficient. Now we have been able to show that star factories like this are also supernova factories," he says.

The radio measurements have also given researchers insight into how radio waves are generated in supernovae and their remnants.

"Our measurements show that a supernova's own magnetic field is what gives rise to its radio emission, not the magnetic fields in the galaxy around it," says Fabien Batejat.

The results will be published in the October 20 issue of the journal Astrophysical Journal.

The team is composed of Fabien Batejat, John Conway and Rossa Hurley from Onsala Space Observatory at Chalmers, Rodrigo Parra (European Southern Observatory, ESO, Santiago, Chile), Philip Diamond (CSIRO, Sydney, Australia), Colin J. Lonsdale (MIT Haystack Observatory, USA) and Carol J. Lonsdale (North American Alma Science Center, NRAO, Charlottesville, USA).

The observations were carried out using telescopes which belong to the European VLBI Network (EVN) together with the Very Long Baseline Array (VLBA). The VLBA is a set of ten radio telescopes located from Hawaii to St. Croix in the U.S. Virgin Islands and operated by the National Radio Astronomy Observatory.

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

Journal Reference:

Fabien Batejat, John E. Conway, Rossa Hurley, Rodrigo Parra, Philip J. Diamond, Colin J. Lonsdale, Carol J. Lonsdale. Resolution of the Compact Radio Continuum Sources in Arp220. Astrophysical Journal, 2011; (in press) [link]

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

View the original article here

Astronomers reveal supernova factory

ScienceDaily (Oct. 2, 2011) — A team led by astronomers at Chalmers and Onsala Space Observatory has detected seven previously unknown supernovae in a galaxy 250 million light years away. Never before have so many supernovae been discovered at the same time in the same galaxy. The discovery proves what astronomers have long believed: that the galaxies which are the universe's most efficient star-factories are also supernova factories.

The astronomers used a worldwide network of radio telescopes in five countries, including Sweden, to be able to create extremely sharp images of the galaxy Arp 220. The scientists observed around 40 radio sources in the center of the galaxy Arp 220. These radio sources are hidden behind thick layers of dust and gas and invisible in ordinary telescopes. To discover the nature of these radio sources, they made measurements at different radio wavelengths and watched how they changed over several years.

"With all the data in place, we can now be certain that all seven of these sources are supernovae: stars that exploded in the last 60 years," says Fabien Batejat, main author of the article about the discovery.

So many supernovae have never before been detected in the same galaxy. The number is nevertheless consistent with how fast stars are forming in Arp 220.

"In Arp 220, we see far more supernovae than in our galaxy. We estimate that a star explodes in Arp 220 once every quarter. In the Milky Way, there is only one supernova per century," says Rodrigo Parra, astronomer at the European Southern Observatory in Chile and member of the team.

John Conway is professor of observational radio astronomy at Chalmers and deputy director of Onsala Space Observatory.

"Arp 220 is well-known as a place where star formation is very efficient. Now we have been able to show that star factories like this are also supernova factories," he says.

The radio measurements have also given researchers insight into how radio waves are generated in supernovae and their remnants.

"Our measurements show that a supernova's own magnetic field is what gives rise to its radio emission, not the magnetic fields in the galaxy around it," says Fabien Batejat.

The results will be published in the October 20 issue of the journal Astrophysical Journal.

The team is composed of Fabien Batejat, John Conway and Rossa Hurley from Onsala Space Observatory at Chalmers, Rodrigo Parra (European Southern Observatory, ESO, Santiago, Chile), Philip Diamond (CSIRO, Sydney, Australia), Colin J. Lonsdale (MIT Haystack Observatory, USA) and Carol J. Lonsdale (North American Alma Science Center, NRAO, Charlottesville, USA).

The observations were carried out using telescopes which belong to the European VLBI Network (EVN) together with the Very Long Baseline Array (VLBA). The VLBA is a set of ten radio telescopes located from Hawaii to St. Croix in the U.S. Virgin Islands and operated by the National Radio Astronomy Observatory.

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

Journal Reference:

Fabien Batejat, John E. Conway, Rossa Hurley, Rodrigo Parra, Philip J. Diamond, Colin J. Lonsdale, Carol J. Lonsdale. Resolution of the Compact Radio Continuum Sources in Arp220. Astrophysical Journal, 2011; (in press) [link]

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View the original article here

Astronomers reveal a cosmic 'axis of evil'

ScienceDaily (June 30, 2011) — Astronomers are puzzled by the announcement that the masses of the largest objects in the universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on 'Scaling Relations of Galaxy Clusters' organised by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.

Clusters of galaxies are the largest gravitationally bound objects in the universe containing thousands of galaxies like the Milky Way and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum: X-ray, optical and millimetre wavelengths, give rise to significantly different results.

Eduardo Rozo, from the University of Chicago, explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the 'Axis of Evil', it is as if the universe is being difficult by keeping back one or two pieces of the jigsaw and so deliberately preventing us from calibrating our weighing scales properly.

More than 40 of the leading cluster astronomers from UK, Europe and the US attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimetre wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitised Sky Survey and new X-ray observations from the XMM-Newton satellite.

ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.

One possible resolution to the 'Axis of Evil' problem discussed at the meeting is a new population of clusters which is optically bright but also X-ray faint. Dr Jim Bartlett (Univ. Paris), who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population which responds differently was a 'frightening prospect' because it overturns age old ideas about the gravitational physics being the same from cluster to cluster.

Chris Collins, LJMU Professor of Cosmology, who organised the meeting said: 'I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don't always talk to their colleagues working at other wavelengths. The results presented are unexpected and all three communities (optical, X-ray and millimetre) will need to work together in the future to figure out what is going on.'

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Royal Astronomical Society (RAS).

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View the original article here

Astronomers find a new class of stellar explosions

ScienceDaily (June 8, 2011) — They're bright and blue-and a bit strange. They're a new type of stellar explosion that was recently discovered by a team of astronomers led by the California Institute of Technology (Caltech). Among the most luminous in the cosmos, these new kinds of supernovae could help researchers better understand star formation, distant galaxies, and what the early universe might have been like.

"We're learning about a whole new class of supernovae that wasn't known before," says Robert Quimby, a Caltech postdoctoral scholar and the lead author on a paper to be published in the June 9 issue of the journal Nature. In addition to finding four explosions of this type, the team also discovered that two previously known supernovae, whose identities had baffled astronomers, also belonged to this new class.

Quimby first made headlines in 2007 when-as a graduate student at the University of Texas, Austin-he discovered what was then the brightest supernova ever found: 100 billion times brighter than the sun and 10 times brighter than most other supernovae. Dubbed 2005ap, it was also a little odd. For one thing, its spectrum-the chemical fingerprint that tells astronomers what the supernova is made of, how far away it is, and what happened when it blew up-was unlike any seen before. It also showed no signs of hydrogen, which is commonly found in most supernovae.

At around the same time, astronomers using the Hubble Space Telescope discovered a mysterious supernova called SCP 06F6. This supernova also had an odd spectrum, though there was nothing that indicated this cosmic blast was similar to 2005ap.

Shri Kulkarni, Caltech's John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science and a coauthor on the paper, recruited Quimby to become a founding member of the Palomar Transient Factory (PTF). The PTF is a project that scans the skies for flashes of light that weren't there before-flashes that signal objects called transients, many of which are supernovae. As part of the PTF, Quimby and his colleagues used the 1.2-meter Samuel Oschin Telescope at Palomar Observatory to discover four new supernovae. After taking spectra with the 10-meter Keck telescopes in Hawaii, the 5.1-meter telescope at Palomar, and the 4.2-meter William Herschel Telescope in the Canary Islands, the astronomers discovered that all four objects had an unusual spectral signature.

Quimby then realized that if you slightly shifted the spectrum of 2005ap-the supernova he had found a couple of years earlier-it looked a lot like these four new objects. The team then plotted all the spectra together. "Boom-it was a perfect match," he recalls.

The astronomers soon determined that shifting the spectrum of SCP 06F6 similarly aligned it with the others. In the end, it turned out that all six supernovae are siblings, and that they all have spectra that are very blue-with the brightest wavelengths shining in the ultraviolet.

According to Quimby, the two mysterious supernovae-2005ap and SCP 06F6-had looked different from one another because 2005ap was 3 billion light-years away while SCP 06F6 was 8 billion light-years away. More distant supernovae have a stronger cosmological redshift, a phenomenon in which the expanding universe stretches the wavelength of the emitted light, shifting supernovae spectra toward the red end.

The four new discoveries, which had features similar to 2005ap and SCP 06F6, were at an intermediate distance, providing the missing link that connected the two previously unexplained supernovae. "That's what was most striking about this-that this was all one unified class," says Mansi Kasliwal, a Caltech graduate student and coauthor on the Nature paper.

Even though astronomers now know these supernovae are related, no one knows much else. "We have a whole new class of objects that can't be explained by any of the models we've seen before," Quimby says. What we do know about them is that they are bright and hot-10,000 to 20,000 degrees Kelvin; that they are expanding rapidly at 10,000 kilometers per second; that they lack hydrogen; and that they take about 50 days to fade away-much longer than most supernovae, whose luminosity is often powered by radioactive decay. So there must be some other mechanism that's making them so bright.

One possible model that would create an explosion with these properties involves a pulsating star about 90 to 130 times the mass of the sun. The pulsations blow off hydrogen-free shells, and when the star exhausts its fuel and explodes as a supernova, the blast heats up those shells to the observed temperatures and luminosities.

A second model requires a star that explodes as a supernova but leaves behind what's called a magnetar, a rapidly spinning dense object with a strong magnetic field. The rotating magnetic field slows the magnetar down as it interacts with the sea of charged particles that fills space, releasing energy. The energy heats the material that was previously blown off during the supernova explosion and can naturally explain the brightness of these events.

The newly discovered supernovae live in dim, small collections of a few billion stars called dwarf galaxies. (Our own Milky Way has 200-400 billion stars.) The supernovae, which are almost a hundred times brighter than their host galaxies, illuminate their environments like distant street lamps lighting up dark roads. They work as a kind of backlight, enabling astronomers to measure the spectrum of the interstellar gas that fills the dwarf galaxies in which the supernovae reside, and revealing each galaxy's composition. Once an observed supernova fades a couple of months later, astronomers can directly study the dwarf galaxy-which would have remained undetected if it weren't for the supernova.

These supernovae could also reveal what ancient stars might have been like, since they most likely originate from stars around a hundred times more massive than the sun-stars that would have been very similar to the first stars in the universe.

"It is really amazing how rich the night sky continues to be," Kulkarni says. "In addition to supernovae, the Palomar Transient Factory is making great advances in stellar astronomy as well."

This research was supported by the National Science Foundation, the United States-Israel Binational Science Foundations, the Israeli Science Foundation, the Department of Energy, the Gordon & Betty Moore foundation, Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, and the Royal Society.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by California Institute of Technology, via EurekAlert!, a service of AAAS. The original article was written by Marcus Woo.

Journal Reference:

R. M. Quimby, S. R. Kulkarni, M. M. Kasliwal, A. Gal-Yam, I. Arcavi, M. Sullivan, P. Nugent, R. Thomas, D. A. Howell, E. Nakar, L. Bildsten, C. Theissen, N. M. Law, R. Dekany, G. Rahmer, D. Hale, R. Smith, E. O. Ofek, J. Zolkower, V. Velur, R. Walters, J. Henning, K. Bui, D. McKenna, D. Poznanski, S. B. Cenko, D. Levitan. Hydrogen-poor superluminous stellar explosions. Nature, 2011; DOI: 10.1038/nature10095

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Crab Nebula Emits Largest Gamma Ray Burst Ever Seen, Puzzles Astronomers

Crab Nebula Emits Largest Gamma Ray Burst Ever Seen, Puzzles Astronomers | Popular Science@import "/files/css/d6aad7f7d1d1484a4d015f8ad6128167.css";@import "/files/css/33f6b7ecb4513ed2fe6c670880a27187.css"; home Login/Register Newsletter Subscribe RSS GadgetsComputersCamerasSmartphonesSmart TVsVideo GamesMore From Our Partner: CEAGCarsConceptsHybridsElectric CarsAuto DIYMore From Our Partner: DriversideScienceFuture of the EnvironmentEnergyHealthPopSci Eco TourTechnologyMilitaryAviationSpaceRobotsDIYProjectsHacksToolsAuto DIYMore From Our Partner: Toolmonger GalleriesVideosColumnsThe GrouseSex FilesGreen Dream How It WorksAuto DIYFeatures Facebook Digg Stumbleupon Reddit Print Email Crab Nebula Emits Largest Gamma Ray Burst Ever Seen, Puzzles Astronomers By Clay Dillow Posted 05.12.2011 at 2:43 pm 5 Comments
The Crab Nebula (And Its Enigmatic Eruption) The nebula set against a full-sky gamma ray map, showing the Crab Nebula's location in the crosshairs. NASA

Something strange is afoot in the Crab Nebula. Famous for beaming a steady dose of radiation at Earth at regular intervals thanks to the spinning neutron star at its center, the nebula has long been of interest to astronomers. So one can imagine their interest when an enormous gamma-ray flare five times more powerful than any previously detected burst from the region, making these "the highest-energy electrons known to be associated with any cosmic source," according to NASA.

The Crab Nebula is basically the remnants of a supernova located about 6,500 light years away (in Taurus, for those of you keeping tabs on the heavens at home). What was once the star’s core is now an expanding gas cloud anchored by a superdense neutron star that rotates 30 times per second, each time swinging a beam of intense radiation toward the Earth.

Related ArticlesAstronomers Find Massive, Previously Undetected Gamma Radiation Bubbles Adorning the Milky WayShedding Some Light on Gamma Ray BurstsStrongest X-Ray Burst Ever Seen Bombards NASA's Swift Observatory, Temporarily Blinding ItTagsTechnology, Clay Dillow, crab nebula, Fermi space telescope, gamma-ray bursts, gamma-rays, SpaceThat’s been going on, from our perspective here, for thousands of years. And it’s been doing so with regularity, 30 times per second, ceaselessly. A handful of short-lived gamma-ray flares have been detected over the years, but nothing that fell outside the range of what’s considered normal cosmic violence.

Then, on April 12, the Fermi Gamma-ray Space Telescope--and later Italy’s AGILE satellite--picked up this monster of a flare 30 times more intense than the nebula’s normal energy output and five times more powerful than any previous uptick in energy. Four days later an even brighter flare erupted. Then, two days after that, the strange activity ceased without explanation.

Astronomers theorize that the flares must be coming from somewhere within a one-third of-a-light-year radius of that central neutron star, and that the area doing the emitting must be close to the size of our own solar system. And to offer some perspective on the energy unleashed, the electrons in these emissions must have energies some 100 times greater than the highest achievable energies in the LHC.

But what caused them is still unknown. The prevailing theory seems to be that the magnetic field around the neutron star suddenly rearranged itself, accelerating particles quickly to nearly the speed of light. As high speed electrons interact with the shifting magnetic field, gamma-rays are produced. Observations are ongoing. In the meantime, it gives us an excuse to post brilliantly pretty images of the Crab Nebula, like the one above.

[NASA]

Previous Article: Video: New ZeroTouch Interface is a Touchscreen Without the ScreenNext Article: Financial Trading Algorithms Aren't Just Making Deals, They're Making War 5 Comments Link to this comment diogogmiranda 05/12/11 at 7:25 pm

Wait, let me understand something here. If the Crab Nebula is 6,500 light years away from here, it means that the light traveling from there takes 6,500 years to get here.
So that happened 6,500 years ago, tight?
If so, how come they're talking in the present? And how long does it take for the radiation to travel compared to the light?

Thanks

Link to this comment yeahilikescience 05/13/11 at 12:28 am

Radiation and light travel at the same speed because visible light is just a form of radiation, the only part of the electromagnetic spectrum that our eyes can detect due to our photoreceptors.

Could it possibly be that something with considerable mass collided with the neutron star, causing a great release of energy because of the star's immense gravity? After all, something approximate to a marshmallow colliding with a neutron star releases about the equivalent energy to an atomic bomb.

Link to this comment yeahilikescience 05/13/11 at 12:30 am

And they're talking in the present because technically speaking, due to space time relativity, all time is now. And because although it happened 6500 years ago 6500 light years away, it is occurring for us to observe now.

Link to this comment OtakuElite 05/14/11 at 1:48 am

What I'm confused about is that the increase in energy means that the rotation of the gas cloud temporarily increased, and "... the magnetic field around the neutron star suddenly rearranged itself, accelerating particles quickly to nearly the speed of light."

So my question is, wouldn't those bursts of increased energy be moving faster than the other pulses, moving out of sequence with the other 30 times per second bursts we can witness here? The statement about nearly the speed of light just leads me to believe it is moving faster then the previous pulses.

Link to this comment JediMindset 05/14/11 at 11:59 am

wow. maybe this has something to do with 2012. its all falling into place. and real science is proving it.

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May 2011: How to Save The Oceans

In this issue, seven bold plans to rescue 71 percent of the planet.

Plus: Blimps are back; a blind race-car driver; the most expensive Internet cable ever; and much more.

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