Scientists study 'galaxy zoo' using Google Maps and thousands of volunteers

ScienceDaily (Nov. 3, 2011) — The reddest galaxies with the largest central bulb show the largest bars -- gigantic central columns of stars and dark matter -- according to a scientific study that used Google Maps to observe the sky. A group of volunteers of more than 200,000 participants of the galaxy classification project Galaxy Zoo contributed to this research.

More than two thirds of spiral galaxies, including our own Milky Way, display a central bar that can extend for thousands of light years. These colossal elongated structures are made up of collections of stars and dark matter which are held together by gravity.

Now a team of researchers from Europe and the USA have measured the bar length of some 5000 galaxies with the help of amateur astronomers. The most precise results (those obtained for 3150 galaxies) have been published in the Monthly Notices of the Royal Astronomical Society.

The study comes under the Galaxy Zoo project, a citizen science initiative in which more than 200,000 volunteers assisted in classifying a million galaxies through images provided by the Sloan Digital Sky Survey astronomical catalogue. As for the bars, 150 amateur astronomers have recorded their observations on a webpage specifically created for this purpose. The page is currently still active despite being closed to any further data entry.

Ben Hoyle, researcher at the Institute of Cosmos Sciences (University of Barcelona, Spain) and coordinator of the study, stresses that "this webpage combines Galaxy Zoo classifications with Google Maps technology." More precisely, the team has used the Google Maps Sky interface which allows to see the sky, especially the galaxies, as seen from Earth's surface.

The redness of bars

"In this way we have compiled some 16,000 measurements of the bars of 5000 galaxies, which is a sample a hundred times greater than previous ones. We have also come to many different conclusions, such as the fact that redder galaxies, which are stopping star formation, have longer bars," says Hoyle.

In the electromagnetic spectrum, the colour red comes from older, cooler stars whereas the colour blue is linked to hotter and younger stars. The study also reveals that the bars tend to be redder than the rest of the galaxy, which indicates that they have an older stellar population.

Other conclusions indicate that those galaxies with a larger bulb (a central agglomeration of stars) have longer bars. In addition, barred galaxies are more likely to display spiral arms than unbarred galaxies.

The images provide examples of barred galaxies with spiral arms. In the first row, the arms are connected to the ring around the bar. In the second row, the arms are connected at the end of the bar and the third row shows a mixture of the two. Image: Ben Hoyle et al./Galaxy Zoo.

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The above story is reprinted from materials provided by Plataforma SINC, via AlphaGalileo.

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Journal Reference:

Ben Hoyle, Karen. L. Masters, Robert C. Nichol, Edward M. Edmondson, Arfon M. Smith, Chris Lintott, Ryan Scranton, Steven Bamford, Kevin Schawinski, Daniel Thomas. Galaxy Zoo: bar lengths in local disc galaxies. Monthly Notices of the Royal Astronomical Society, 2011; 415 (4): 3627 DOI: 10.1111/j.1365-2966.2011.18979.x

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View the original article here

Starburst captured: Students photograph exploding star in pinwheel galaxy

ScienceDaily (Oct. 18, 2011) — In the Pinwheel Galaxy some 21 million light years from Earth, a supernova beams brightly, out-shining its cosmic neighbors and causing a stir among starwatchers.

Students in University of Delaware Prof. Judi Provencal's Observational Astronomy class (PHYS 469) photographed the exploding star last week using the telescope at Mt. Cuba Astronomical Observatory in Greenville, Del., which has a lens spanning 24 inches in diameter.

"The supernova, a star that is blowing itself to bits, is the brightest object in the lower center of the image," Provencal notes. "It is the brightest supernova in the last 20 years and might be visible with binoculars."

The bursting star, known as PTF 11kly, will eventually fade over the next year or so and then turn into a neutron star or a black hole. The material ejected when it exploded may form new stars.

According to Provencal, PTF 11kly is a "Type 1a" supernova, which means it's half of a "stellar team" known as a binary star. One of the stars is an "ordinary" star, and the other is a white dwarf, a super-dense star that is the size of Earth, but has the mass of the sun. Because it doesn't have nuclear reactions firing away in its core, the white dwarf does not generate any internal energy. Instead, it's supported against gravity by "electron degeneracy pressure" which occurs when a huge number of electrons are compacted tightly together in a small volume.

The two stars of the binary team orbit very closely together, so close that the "ordinary" star transfers material to the white dwarf. When the white dwarf gains enough material that it reaches a critical mass (about 1.4 times the mass of the sun), electron degeneracy pressure fails and the star will collapse in on itself. This produces a lot of energy, which we see as the supernova, Provencal explains.

"These are the types of supernova that were used to determine that the universe is actually accelerating in its expansion, which has led to the whole field of dark energy," Provencal says.

The Pinwheel Galaxy inhabited by the PTF 11kly supernova was discovered in 1781 by French astronomer Pierre Mechain, who thought it was a nebula, a gas cloud from which new stars are born. Erwin Hubble later would show that it is indeed a full-fledged galaxy.

Mechain's fellow astronomer Charles Messier would include it as an item, today still referred to as "Messier 101," or M101, in his 1781 astronomical catalog.

"Messier's list was supposed to help with comet hunting since it was a list of fuzzy objects that didn't move in the sky. Comet hunting was a big deal back then," notes Provencal.

The Pinwheel Galaxy is a spiral galaxy much like our own Milky Way. It's called a spiral galaxy for the spiral arms or "spokes" that curve away from a center disk of highly concentrated stars. The stars in these spokes are younger and thus hotter and brighter than the stars at the center.

Although the Pinwheel Galaxy is playing host to the brightest, nearest supernova seen from Earth in years, starwatchers should know that our own Milky Way also sports supernovae from time to time -- the most recent one was recorded in 1572, Provencal says.

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The above story is reprinted from materials provided by University of Delaware. The original article was written by Tracey Bryant.

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View the original article here

Starburst captured: Students photograph exploding star in pinwheel galaxy

ScienceDaily (Oct. 18, 2011) — In the Pinwheel Galaxy some 21 million light years from Earth, a supernova beams brightly, out-shining its cosmic neighbors and causing a stir among starwatchers.

Students in University of Delaware Prof. Judi Provencal's Observational Astronomy class (PHYS 469) photographed the exploding star last week using the telescope at Mt. Cuba Astronomical Observatory in Greenville, Del., which has a lens spanning 24 inches in diameter.

"The supernova, a star that is blowing itself to bits, is the brightest object in the lower center of the image," Provencal notes. "It is the brightest supernova in the last 20 years and might be visible with binoculars."

The bursting star, known as PTF 11kly, will eventually fade over the next year or so and then turn into a neutron star or a black hole. The material ejected when it exploded may form new stars.

According to Provencal, PTF 11kly is a "Type 1a" supernova, which means it's half of a "stellar team" known as a binary star. One of the stars is an "ordinary" star, and the other is a white dwarf, a super-dense star that is the size of Earth, but has the mass of the sun. Because it doesn't have nuclear reactions firing away in its core, the white dwarf does not generate any internal energy. Instead, it's supported against gravity by "electron degeneracy pressure" which occurs when a huge number of electrons are compacted tightly together in a small volume.

The two stars of the binary team orbit very closely together, so close that the "ordinary" star transfers material to the white dwarf. When the white dwarf gains enough material that it reaches a critical mass (about 1.4 times the mass of the sun), electron degeneracy pressure fails and the star will collapse in on itself. This produces a lot of energy, which we see as the supernova, Provencal explains.

"These are the types of supernova that were used to determine that the universe is actually accelerating in its expansion, which has led to the whole field of dark energy," Provencal says.

The Pinwheel Galaxy inhabited by the PTF 11kly supernova was discovered in 1781 by French astronomer Pierre Mechain, who thought it was a nebula, a gas cloud from which new stars are born. Erwin Hubble later would show that it is indeed a full-fledged galaxy.

Mechain's fellow astronomer Charles Messier would include it as an item, today still referred to as "Messier 101," or M101, in his 1781 astronomical catalog.

"Messier's list was supposed to help with comet hunting since it was a list of fuzzy objects that didn't move in the sky. Comet hunting was a big deal back then," notes Provencal.

The Pinwheel Galaxy is a spiral galaxy much like our own Milky Way. It's called a spiral galaxy for the spiral arms or "spokes" that curve away from a center disk of highly concentrated stars. The stars in these spokes are younger and thus hotter and brighter than the stars at the center.

Although the Pinwheel Galaxy is playing host to the brightest, nearest supernova seen from Earth in years, starwatchers should know that our own Milky Way also sports supernovae from time to time -- the most recent one was recorded in 1572, Provencal says.

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Story Source:

The above story is reprinted from materials provided by University of Delaware. The original article was written by Tracey Bryant.

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

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

Light from galaxy clusters confirms general theory of relativity

ScienceDaily (Sep. 28, 2011) — All observations in astronomy are based on light (electromagnetic radiation) emitted from stars and galaxies and, according to the general theory of relativity, the light will be affected by gravity. At the same time all interpretations in astronomy are based on the correctness of the theory of relatively, but it has been difficult to accurately test Einstein's theory of gravity on scales larger than the solar system. Now astrophysicists at the Dark Cosmology Centre at the Niels Bohr Institute have managed to measure how the light is affected by gravity on its way out of galaxy clusters. The observations confirm the theoretical predictions.

The results have been published in the scientific journal, Nature.

Observations of large distances in the universe are based on measurements of the redshift, which is a phenomenon where the wavelength of the light from distant galaxies is shifted more and more towards the red with greater distance. The redshift indicates how much the universe has expanded from when the light left until it was measured on Earth. Furthermore, according to Einstein's general theory of relativity, the light and thus the redshift is also affected by the gravity from large masses like galaxy clusters and causes a gravitational redshift of the light. But the gravitational influence on light has never before been measured on a cosmological scale.

"It is really wonderful. We live in an era with the technological ability to actually measure such phenomena as cosmological gravitational redshift," says astrophysicist Radek Wojtak, Dark Cosmology Centre under the Niels Bohr Institute at the University of Copenhagen.

Galaxy clusters in the searchlight

Radek Wojtak, together with colleagues Steen Hansen and Jens Hjorth, has analysed measurements of light from galaxies in approximately 8,000 galaxy clusters. Galaxy clusters are accumulations of thousands of galaxies, held together by their own gravity. This gravity affects the light being sent out into space from the galaxies.

The researchers have studied the galaxies lying in the middle of the galaxy clusters and those lying on the periphery and measured the wavelengths of the light.

"We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to 'crawl' out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge," explains Radek Wojtak.

Then he measured the entire galaxy cluster's total mass and with that got the gravitational potential. By using the general theory of relativity he could now calculate the gravitational redshift for the different locations of the galaxies.

"It turned out that the theoretical calculations of the gravitational redshift based on the general theory of relativity was in complete agreement with the astronomical observations. Our analysis of observations of galaxy clusters show that the redshift of the light is proportionally offset in relation to the gravitational influence from the galaxy cluster's gravity. In that way our observations confirm the theory of relativity," explains Radek Wojtak.

New light on the dark universe

The discovery has significance for the phenomena in the universe that researchers are working to unravel. It is the mysterious dark universe -- dark matter and dark energy.

In addition to the visible celestial bodies like stars, planets and galaxies, the universe consists of a large amount of matter, which researchers can work out that it must be there, but which cannot be observed as it neither emits nor reflects light. It is invisible and is therefore called dark matter. No one knows what dark matter is, but they know what the mass and thus the gravity must be. The new results for gravitational redshift do not change the researchers' modelling for the presence of dark matter.

Another of the main components of the universe is dark energy, which according to the theoretical models acts like a kind of vacuum that causes the expansion of the universe to accelerate. According to the calculations, which are based on Einstein's theory of relativity, dark energy constitutes 72 percent of the structure of the universe. Many alternative theories try to explain the accelerating expansion without the presence of dark energy.

Theory tested on a large scale

"Now the general theory of relativity has been tested on a cosmological scale and this confirms that the general theory of relativity works and that means that there is a strong indication for the presence of dark energy," explains Radek Wojtak.

The new gravitation results thus contribute a new piece of insight to the understanding of the hidden, dark universe and provide a greater understanding of the nature of the visible universe.

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

Journal Reference:

Radoslaw Wojtak, Steen H. Hansen, Jens Hjorth. Gravitational redshift of galaxies in clusters as predicted by general relativity. Nature, 2011; 477 (7366): 567 DOI: 10.1038/nature10445

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

Galaxy caught blowing bubbles

ScienceDaily (Oct. 1, 2011) — Hubble's famous images of galaxies typically show elegant spirals or soft-edged ellipses. But these neat forms are only representative of large galaxies. Smaller galaxies like the dwarf irregular galaxy Holmberg II come in many shapes and types that are harder to classify. This galaxy's indistinct shape is punctuated by huge glowing bubbles of gas, captured in a new image from the NASA/ESA Hubble Space Telescope.

The intricate glowing shells of gas in Holmberg II were created by the energetic lifecycles of many generations of stars. High-mass stars form in dense regions of gas, and later in life expel strong stellar winds that blow away the surrounding material. At the very end of their lives, they explode in as a supernova. Shock waves rip through these less dense regions blowing out and heating the gas, forming the delicate shells we see today.

Holmberg II is a patchwork of dense star-forming regions and extensive barren areas with less material, which can stretch across thousands of light-years. As a dwarf galaxy, it has neither the spiral arms typical of galaxies like the Milky Way nor the dense nucleus of an elliptical galaxy. This makes Holmberg II, gravitationally speaking, a gentle haven where fragile structures such as these bubbles can hold their shape.

While the galaxy is unremarkable in size, Holmberg II does have some intriguing features. As well as its unusual appearance -- which earned it a place in Halton Arp's Atlas of Peculiar Galaxies, a treasure trove of weird and wonderful objects -- the galaxy hosts an ultraluminous X-ray source in the middle of three gas bubbles in the top right of the image. There are competing theories as to what causes this powerful radiation -- one intriguing possibility is an intermediate-mass black hole which is pulling in material from its surroundings.

This colourful image is a composite of visible and near-infrared exposures taken using the Wide Field Channel of Hubble's Advanced Camera for Surveys.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by ESA/Hubble Information Centre.

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

Light from galaxy clusters confirms general theory of relativity

ScienceDaily (Sep. 28, 2011) — All observations in astronomy are based on light (electromagnetic radiation) emitted from stars and galaxies and, according to the general theory of relativity, the light will be affected by gravity. At the same time all interpretations in astronomy are based on the correctness of the theory of relatively, but it has been difficult to accurately test Einstein's theory of gravity on scales larger than the solar system. Now astrophysicists at the Dark Cosmology Centre at the Niels Bohr Institute have managed to measure how the light is affected by gravity on its way out of galaxy clusters. The observations confirm the theoretical predictions.

The results have been published in the scientific journal, Nature.

Observations of large distances in the universe are based on measurements of the redshift, which is a phenomenon where the wavelength of the light from distant galaxies is shifted more and more towards the red with greater distance. The redshift indicates how much the universe has expanded from when the light left until it was measured on Earth. Furthermore, according to Einstein's general theory of relativity, the light and thus the redshift is also affected by the gravity from large masses like galaxy clusters and causes a gravitational redshift of the light. But the gravitational influence on light has never before been measured on a cosmological scale.

"It is really wonderful. We live in an era with the technological ability to actually measure such phenomena as cosmological gravitational redshift," says astrophysicist Radek Wojtak, Dark Cosmology Centre under the Niels Bohr Institute at the University of Copenhagen.

Galaxy clusters in the searchlight

Radek Wojtak, together with colleagues Steen Hansen and Jens Hjorth, has analysed measurements of light from galaxies in approximately 8,000 galaxy clusters. Galaxy clusters are accumulations of thousands of galaxies, held together by their own gravity. This gravity affects the light being sent out into space from the galaxies.

The researchers have studied the galaxies lying in the middle of the galaxy clusters and those lying on the periphery and measured the wavelengths of the light.

"We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to 'crawl' out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge," explains Radek Wojtak.

Then he measured the entire galaxy cluster's total mass and with that got the gravitational potential. By using the general theory of relativity he could now calculate the gravitational redshift for the different locations of the galaxies.

"It turned out that the theoretical calculations of the gravitational redshift based on the general theory of relativity was in complete agreement with the astronomical observations. Our analysis of observations of galaxy clusters show that the redshift of the light is proportionally offset in relation to the gravitational influence from the galaxy cluster's gravity. In that way our observations confirm the theory of relativity," explains Radek Wojtak.

New light on the dark universe

The discovery has significance for the phenomena in the universe that researchers are working to unravel. It is the mysterious dark universe -- dark matter and dark energy.

In addition to the visible celestial bodies like stars, planets and galaxies, the universe consists of a large amount of matter, which researchers can work out that it must be there, but which cannot be observed as it neither emits nor reflects light. It is invisible and is therefore called dark matter. No one knows what dark matter is, but they know what the mass and thus the gravity must be. The new results for gravitational redshift do not change the researchers' modelling for the presence of dark matter.

Another of the main components of the universe is dark energy, which according to the theoretical models acts like a kind of vacuum that causes the expansion of the universe to accelerate. According to the calculations, which are based on Einstein's theory of relativity, dark energy constitutes 72 percent of the structure of the universe. Many alternative theories try to explain the accelerating expansion without the presence of dark energy.

Theory tested on a large scale

"Now the general theory of relativity has been tested on a cosmological scale and this confirms that the general theory of relativity works and that means that there is a strong indication for the presence of dark energy," explains Radek Wojtak.

The new gravitation results thus contribute a new piece of insight to the understanding of the hidden, dark universe and provide a greater understanding of the nature of the visible universe.

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and Google +1:

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Story Source:

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

Journal Reference:

Radoslaw Wojtak, Steen H. Hansen, Jens Hjorth. Gravitational redshift of galaxies in clusters as predicted by general relativity. Nature, 2011; 477 (7366): 567 DOI: 10.1038/nature10445

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

Galaxy caught blowing bubbles

ScienceDaily (Oct. 1, 2011) — Hubble's famous images of galaxies typically show elegant spirals or soft-edged ellipses. But these neat forms are only representative of large galaxies. Smaller galaxies like the dwarf irregular galaxy Holmberg II come in many shapes and types that are harder to classify. This galaxy's indistinct shape is punctuated by huge glowing bubbles of gas, captured in a new image from the NASA/ESA Hubble Space Telescope.

The intricate glowing shells of gas in Holmberg II were created by the energetic lifecycles of many generations of stars. High-mass stars form in dense regions of gas, and later in life expel strong stellar winds that blow away the surrounding material. At the very end of their lives, they explode in as a supernova. Shock waves rip through these less dense regions blowing out and heating the gas, forming the delicate shells we see today.

Holmberg II is a patchwork of dense star-forming regions and extensive barren areas with less material, which can stretch across thousands of light-years. As a dwarf galaxy, it has neither the spiral arms typical of galaxies like the Milky Way nor the dense nucleus of an elliptical galaxy. This makes Holmberg II, gravitationally speaking, a gentle haven where fragile structures such as these bubbles can hold their shape.

While the galaxy is unremarkable in size, Holmberg II does have some intriguing features. As well as its unusual appearance -- which earned it a place in Halton Arp's Atlas of Peculiar Galaxies, a treasure trove of weird and wonderful objects -- the galaxy hosts an ultraluminous X-ray source in the middle of three gas bubbles in the top right of the image. There are competing theories as to what causes this powerful radiation -- one intriguing possibility is an intermediate-mass black hole which is pulling in material from its surroundings.

This colourful image is a composite of visible and near-infrared exposures taken using the Wide Field Channel of Hubble's Advanced Camera for Surveys.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by ESA/Hubble Information Centre.

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

Nearby galaxy boasts two monster black holes, both active

ScienceDaily (June 11, 2011) — A study using NASA's Swift satellite and the Chandra X-ray Observatory has found a second supersized black hole at the heart of an unusual nearby galaxy already known to be sporting one.

The galaxy, which is known as Markarian 739 or NGC 3758, lies 425 million light-years away toward the constellation Leo. Only about 11,000 light-years separate the two cores, each of which contains a black hole gorging on infalling gas.

The study will appear in a forthcoming issue of The Astrophysical Journal Letters.

"At the hearts of most large galaxies, including our own Milky Way, lies a supermassive black hole weighing millions of times the sun's mass," said Michael Koss, the study's lead author at NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland in College Park (UMCP). "Some of them radiate billions of times as much energy as the sun."

Astronomers refer to galaxy centers exhibiting such intense emission as active galactic nuclei (AGN). Yet as common as monster black holes are, only about one percent of them are currently powerful AGN. Binary AGN are rarer still: Markarian 739 is only the second identified within half a billion light-years.

Many scientists think that disruptive events like galaxy collisions trigger AGN to switch on by sending large amounts of gas toward the black hole. As the gas spirals inward, it becomes extremely hot and radiates huge amounts of energy.

Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping high-energy X-ray sources all around the sky. The survey is sensitive to AGN up to 650 million light-years away and has uncovered dozens of previously unrecognized systems. Follow-up studies by Koss and colleagues published in 2010 reveal that about a quarter of the Swift BAT AGN were either interacting or in close pairs, with perhaps 60 percent of them poised to merge in another billion years.

"If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," said coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double AGN, so we turned to Chandra for help."

Swift's BAT instrument is scanning one-tenth of the sky at any given moment, its X-ray survey growing more sensitive every year as its exposure increases. Where Swift's BAT provided a wide-angle view, the X-ray telescope aboard the Chandra X-ray Observatory acted like a zoom lens and resolved details a hundred times smaller.

For decades, astronomers have known that the eastern nucleus of Markarian 739 contains a black hole that is actively accreting matter and generating prodigious energy. The Chandra study shows that its western neighbor is too. This makes the galaxy one of the nearest and clearest cases of a binary AGN.

The distance separating the two black holes is about a third of the distance separating the solar system from the center of our own galaxy. The dual AGN of Markarian 739 is the second-closest known, both in terms of distance from one another and distance from Earth. However, another galaxy known as NGC 6240 holds both records.

How did the second AGN remain hidden for so long? "Markarian 739 West shows no evidence of being an AGN in visible, ultraviolet and radio observations," said coauthor Sylvain Veilleux, a professor of astronomy at UMCP. "This highlights the critical importance of high-resolution observations at high X-ray energies in locating binary AGN."

The research team also includes Ezequiel Treister and David Sanders at the University of Hawaii's Institute for Astronomy in Honolulu, Kevin Schawinski at Yale University in New Haven, Conn., and Ranjan Vasudevan, Neal Miller and Margaret Trippe at the University of Maryland, College Park.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, the Los Alamos National Laboratory in New Mexico, and General Dynamics in Falls Church, Va.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

The Marshall Space Flight Center manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information, images and video, please visit: http://www.nasa.gov/mission_pages/swift/bursts/monster-black-holes.html

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Goddard Space Flight Center.

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

Nearby galaxy boasts two monster black holes, both active

ScienceDaily (June 11, 2011) — A study using NASA's Swift satellite and the Chandra X-ray Observatory has found a second supersized black hole at the heart of an unusual nearby galaxy already known to be sporting one.

The galaxy, which is known as Markarian 739 or NGC 3758, lies 425 million light-years away toward the constellation Leo. Only about 11,000 light-years separate the two cores, each of which contains a black hole gorging on infalling gas.

The study will appear in a forthcoming issue of The Astrophysical Journal Letters.

"At the hearts of most large galaxies, including our own Milky Way, lies a supermassive black hole weighing millions of times the sun's mass," said Michael Koss, the study's lead author at NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland in College Park (UMCP). "Some of them radiate billions of times as much energy as the sun."

Astronomers refer to galaxy centers exhibiting such intense emission as active galactic nuclei (AGN). Yet as common as monster black holes are, only about one percent of them are currently powerful AGN. Binary AGN are rarer still: Markarian 739 is only the second identified within half a billion light-years.

Many scientists think that disruptive events like galaxy collisions trigger AGN to switch on by sending large amounts of gas toward the black hole. As the gas spirals inward, it becomes extremely hot and radiates huge amounts of energy.

Since 2004, the Burst Alert Telescope (BAT) aboard Swift has been mapping high-energy X-ray sources all around the sky. The survey is sensitive to AGN up to 650 million light-years away and has uncovered dozens of previously unrecognized systems. Follow-up studies by Koss and colleagues published in 2010 reveal that about a quarter of the Swift BAT AGN were either interacting or in close pairs, with perhaps 60 percent of them poised to merge in another billion years.

"If two galaxies collide and each possesses a supermassive black hole, there should be times when both black holes switch on as AGN," said coauthor Richard Mushotzky, professor of astronomy at UMCP. "We weren't seeing many double AGN, so we turned to Chandra for help."

Swift's BAT instrument is scanning one-tenth of the sky at any given moment, its X-ray survey growing more sensitive every year as its exposure increases. Where Swift's BAT provided a wide-angle view, the X-ray telescope aboard the Chandra X-ray Observatory acted like a zoom lens and resolved details a hundred times smaller.

For decades, astronomers have known that the eastern nucleus of Markarian 739 contains a black hole that is actively accreting matter and generating prodigious energy. The Chandra study shows that its western neighbor is too. This makes the galaxy one of the nearest and clearest cases of a binary AGN.

The distance separating the two black holes is about a third of the distance separating the solar system from the center of our own galaxy. The dual AGN of Markarian 739 is the second-closest known, both in terms of distance from one another and distance from Earth. However, another galaxy known as NGC 6240 holds both records.

How did the second AGN remain hidden for so long? "Markarian 739 West shows no evidence of being an AGN in visible, ultraviolet and radio observations," said coauthor Sylvain Veilleux, a professor of astronomy at UMCP. "This highlights the critical importance of high-resolution observations at high X-ray energies in locating binary AGN."

The research team also includes Ezequiel Treister and David Sanders at the University of Hawaii's Institute for Astronomy in Honolulu, Kevin Schawinski at Yale University in New Haven, Conn., and Ranjan Vasudevan, Neal Miller and Margaret Trippe at the University of Maryland, College Park.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, the Los Alamos National Laboratory in New Mexico, and General Dynamics in Falls Church, Va.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

The Marshall Space Flight Center manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information, images and video, please visit: http://www.nasa.gov/mission_pages/swift/bursts/monster-black-holes.html

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Goddard Space Flight Center.

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

Dark energy is driving universe apart: NASA's Galaxy Evolution Explorer finds dark energy repulsive

ScienceDaily (May 19, 2011) — A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds.

The survey used data from NASA's space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The findings offer new support for the favored theory of how dark energy works -- as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein's concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.

"The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster," said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. "The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn't be seeing these constant effects of dark energy throughout time."

Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.

The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called "standard candles," which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.

The new survey provides two separate methods for independently checking these results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. Astronomers began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer.

"The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study," said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. "It provided the scaffolding for this enormous 3-D map."

The team acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.

Blake and his colleagues used this "standard ruler" to determine the distance from the galaxy pairs to Earth. As with the supernovae studies, this distance data was combined with information about the speeds the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.

The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy's repulsive force.

"Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the big bang, is speeding up," said Jon Morse, astrophysics division director at NASA Headquarters in Washington. "Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy."

For more information about NASA's Galaxy Evolution Explorer, visit: http://www.nasa.gov/galex and http://www.galex.caltech.edu .

Story Source:

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

Journal Reference:

Chris Blake, Sarah Brough, Matthew Colless, Warrick Couch, Scott Croom, Tamara Davis, Michael J. Drinkwater, Karl Forster, Karl Glazebrook, Ben Jelliffe, Russell J. Jurek, I-hui Li, Barry Madore, Chris Martin, Kevin Pimbblet, Gregory B. Poole, Michael Pracy, Rob Sharp, Emily Wisnioski, David Woods, Ted Wyder. The WiggleZ Dark Energy Survey: the selection function and z= 0.6 galaxy power spectrum. Monthly Notices of the Royal Astronomical Society, 2010; DOI: 10.1111/j.1365-2966.2010.16747.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

Dark energy is driving universe apart: NASA's Galaxy Evolution Explorer finds dark energy repulsive

ScienceDaily (May 19, 2011) — A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds.

The survey used data from NASA's space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The findings offer new support for the favored theory of how dark energy works -- as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein's concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.

"The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster," said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. "The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn't be seeing these constant effects of dark energy throughout time."

Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.

The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called "standard candles," which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.

The new survey provides two separate methods for independently checking these results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. Astronomers began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer.

"The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study," said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. "It provided the scaffolding for this enormous 3-D map."

The team acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.

Blake and his colleagues used this "standard ruler" to determine the distance from the galaxy pairs to Earth. As with the supernovae studies, this distance data was combined with information about the speeds the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.

The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy's repulsive force.

"Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the big bang, is speeding up," said Jon Morse, astrophysics division director at NASA Headquarters in Washington. "Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy."

For more information about NASA's Galaxy Evolution Explorer, visit: http://www.nasa.gov/galex and http://www.galex.caltech.edu .

Story Source:

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

Journal Reference:

Chris Blake, Sarah Brough, Matthew Colless, Warrick Couch, Scott Croom, Tamara Davis, Michael J. Drinkwater, Karl Forster, Karl Glazebrook, Ben Jelliffe, Russell J. Jurek, I-hui Li, Barry Madore, Chris Martin, Kevin Pimbblet, Gregory B. Poole, Michael Pracy, Rob Sharp, Emily Wisnioski, David Woods, Ted Wyder. The WiggleZ Dark Energy Survey: the selection function and z= 0.6 galaxy power spectrum. Monthly Notices of the Royal Astronomical Society, 2010; DOI: 10.1111/j.1365-2966.2010.16747.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

Galaxy NGC 4214: A star formation laboratory

ScienceDaily (May 13, 2011) — Size isn't everything ... in astronomy, at least. Dwarf galaxy NGC 4214 may be small, but what it lacks in size it makes up for in content. It is packed with everything an astronomer could ask for, from hot, young star-forming regions to old clusters with red supergiants.

The intricate patterns of glowing ionised hydrogen gas, cavities blown clear of gas by stellar wind, and bright stellar clusters of NGC 4214 can be seen in this optical and near-infrared image, taken using the Wide Field Camera 3 (WFC3) instrument on the NASA/ESA Hubble Space Telescope.

A huge heart-shaped cavity -- possibly the galaxy's most eye-catching feature -- can be seen at the centre of the image. Inside this hole lies a large cluster of massive, young stars ranging in temperature from 10 000 to 50 000 degrees Celsius. Their strong stellar winds are responsible for the creation of this hollow area. The resulting lack of gas prevents any further star formation from occurring in this region.

Located around 10 million light-years away in the constellation of Canes Venatici (The Hunting Dogs), the galaxy's relative close proximity to us, combined with the wide variety of evolutionary stages among the stars, makes it an ideal laboratory to research what triggers star formation and evolution. By chance, there is relatively little interstellar dust between us and NGC 4214, making our measurements of it more accurate.

NGC 4214 contains a large amount of gas, some of which can be seen glowing red in the image, providing abundant material for star formation. The area with the most hydrogen gas, and consequently, the youngest clusters of stars (around two million years old), lies in the upper part of this Hubble image. Like most of the features in the image, this area is visible due to ionisation of the surrounding gas by the ultraviolet light of a young cluster of stars within.

Observations of this dwarf galaxy have also revealed clusters of much older red supergiant stars that we see at a late stage in their evolution. Additional older stars can be seen dotted all across the galaxy. While these are dominant in infrared emission they can only be seen shining faintly in this visible-light image. The variety of stars at different stages in their evolution, indicate that the recent and ongoing starburst periods are by no means the first, and the galaxy's numerous ionised hydrogen regions suggest they will not be the last.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by ESA/Hubble Information Centre.

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

Supernova and star birth in the Meathook Galaxy

ScienceDaily (May 4, 2011) — The Meathook Galaxy, or NGC 2442, has a dramatically lopsided shape. One spiral arm is tightly folded in on itself and host to a recent supernova, while the other, dotted with recent star formation, extends far out from the nucleus. The NASA/ESA Hubble Space Telescope and the MPG/ESO 2.2-metre telescope have captured two contrasting views of this asymmetric spiral galaxy.

The Meathook Galaxy, or NGC 2442, in the southern constellation of Volans (The Flying Fish), is easily recognised for its asymmetric spiral arms. The galaxy's lopsided appearance is thought to be due to gravitational interactions with another galaxy at some point in its history -- though astronomers have not so far been able to positively identify the culprit.

A close-up image from the NASA/ESA Hubble Space Telescope focuses on the galaxy's nucleus and the more compact of its two spiral arms. In 1999, a massive star at the end of its life exploded in this arm in a supernova. By comparing older ground-based observations, previous Hubble images made in 2001, and these shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments. By the time of this image the supernova itself had faded and is not visible.

A much broader view, taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla, Chile, very clearly shows the double hook shape that gives the galaxy its nickname. This image also captures several other galaxies close to NGC 2442 as well as many more remote galaxies that form a rich backdrop. Although the Wide Field Imager, on the ground, cannot approach the sharpness of images from Hubble in space, it can cover a much bigger section of sky in a single exposure. The two tools often provide complementary information to astronomers.

ESO's observations also highlight the other end of the life cycle of stars from Hubble. Dotted across much of the galaxy, and particularly in the longer of the two spiral arms, are patches of pink and red. This colour comes from hydrogen gas in star-forming regions: as the powerful radiation of new-born stars excites the gas in the clouds they formed from, it glows a bright shade of red.

The interaction with another galaxy that gave the Meathook Galaxy its unusual asymmetric shape is also likely to have been the trigger of this recent episode of star formation. The same tidal forces that deformed the galaxy disrupted clouds of gas and triggered their gravitational collapse.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by ESA/Hubble Information Centre.

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

Galaxy NGC 4214: A star formation laboratory

ScienceDaily (May 13, 2011) — Size isn't everything ... in astronomy, at least. Dwarf galaxy NGC 4214 may be small, but what it lacks in size it makes up for in content. It is packed with everything an astronomer could ask for, from hot, young star-forming regions to old clusters with red supergiants.

The intricate patterns of glowing ionised hydrogen gas, cavities blown clear of gas by stellar wind, and bright stellar clusters of NGC 4214 can be seen in this optical and near-infrared image, taken using the Wide Field Camera 3 (WFC3) instrument on the NASA/ESA Hubble Space Telescope.

A huge heart-shaped cavity -- possibly the galaxy's most eye-catching feature -- can be seen at the centre of the image. Inside this hole lies a large cluster of massive, young stars ranging in temperature from 10 000 to 50 000 degrees Celsius. Their strong stellar winds are responsible for the creation of this hollow area. The resulting lack of gas prevents any further star formation from occurring in this region.

Located around 10 million light-years away in the constellation of Canes Venatici (The Hunting Dogs), the galaxy's relative close proximity to us, combined with the wide variety of evolutionary stages among the stars, makes it an ideal laboratory to research what triggers star formation and evolution. By chance, there is relatively little interstellar dust between us and NGC 4214, making our measurements of it more accurate.

NGC 4214 contains a large amount of gas, some of which can be seen glowing red in the image, providing abundant material for star formation. The area with the most hydrogen gas, and consequently, the youngest clusters of stars (around two million years old), lies in the upper part of this Hubble image. Like most of the features in the image, this area is visible due to ionisation of the surrounding gas by the ultraviolet light of a young cluster of stars within.

Observations of this dwarf galaxy have also revealed clusters of much older red supergiant stars that we see at a late stage in their evolution. Additional older stars can be seen dotted all across the galaxy. While these are dominant in infrared emission they can only be seen shining faintly in this visible-light image. The variety of stars at different stages in their evolution, indicate that the recent and ongoing starburst periods are by no means the first, and the galaxy's numerous ionised hydrogen regions suggest they will not be the last.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by ESA/Hubble Information Centre.

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