Posted on by Tammy Plotner

Supernova Primo – Out To Far Frontiers

The top image shows part of the Hubble Ultra Deep Field, the region where astronomers were looking for a supernova blast. The white box pinpoints the area where the supernova is later seen. The image combines observations taken in visible and near-infrared light with the Advanced Camera for Surveys and the Wide Field Camera 3. The image at bottom left, taken by the Wide Field Camera 3, is a close-up of the field without the supernova. A new bright object, identified as the supernova, appears in the Wide Field Camera 3 image at bottom right. Credit: NASA, ESA, A. Riess (Space Telescope Science Institute and The Johns Hopkins University), and S. Rodney (The Johns Hopkins University)

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Its nickname is SN Primo and it’s the farthest Type Ia supernova to have its distance spectroscopically confirmed. When the progenitor star exploded some 9 billion years ago, Primo sent its brilliant beacon of light across time and space to be captured by the Hubble Space Telescope. It’s all part and parcel of a three-year project dealing specifically with Type Ia supernovae. By splitting its light into constituent colors, researchers can verify its distance by redshift and help astronomers better understand not only the expanding Universe, but the constraints of dark energy.

“For decades, astronomers have harnessed the power of Hubble to unravel the mysteries of the Universe,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “This new observation builds upon the revolutionary research using Hubble that won astronomers the 2011 Nobel Prize in Physics, while bringing us a step closer to understanding the nature of dark energy which drives the cosmic acceleration.”

Type Ia supernovae are theorized to have originated from white dwarf stars which have collected an excess of material from their companions and exploded. Because of their remote nature, they have been used to measure great distances with acceptable accuracy. Enter the CANDELS+CLASH Supernova Project… a type of census which utilizes the sharpness and versatility of Hubble’s Wide Field Camera 3 (WFC3) to aid astronomers in the search for supernovae in near- infrared light and verify their distance with spectroscopy. CANDELS is the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and CLASH is the Cluster Lensing and Supernova Survey with Hubble.

“In our search for supernovae, we had gone as far as we could go in optical light,” said Adam Riess, the project’s lead investigator, at the Space Telescope Science Institute and The Johns Hopkins University in Baltimore, Md. “But it’s only the beginning of what we can do in infrared light. This discovery demonstrates that we can use the Wide Field Camera 3 to search for supernovae in the distant Universe.”

However, discovering a supernova like Primo just doesn’t happen overnight. It took the research team several months of work and a huge amount of near-infrared images to locate the faint signature. After capturing the elusive target in October 2010, it was time to employ the WFC3’s spectrometer to validate SN Primo’s distance and analyze the spectra for confirmation of a Type Ia supernova event. Once verified, the team continued to image SN Primo for the next eight months – collecting data as it faded away. By engaging the Hubble in this type of census, astronomers hope to further their understanding of how such events are created. If they should discover that Type Ia supernova don’t always appear the same, it may lead to a way of categorizing those changes and aid in measuring dark energy. Riess and two other astronomers shared the 2011 Nobel Prize in Physics for discovering dark energy 13 years ago, using Type Ia supernova to plot the Universe’s expansion rate.

“If we look into the early Universe and measure a drop in the number of supernovae, then it could be that it takes a long time to make a Type Ia supernova,” said team member Steve Rodney of The Johns Hopkins University. “Like corn kernels in a pan waiting for the oil to heat up, the stars haven’t had enough time at that epoch to evolve to the point of explosion. However, if supernovae form very quickly, like microwave popcorn, then they will be immediately visible, and we’ll find many of them, even when the Universe was very young. Each supernova is unique, so it’s possible that there are multiple ways to make a supernova.”

Original Story Source: Hubble Site News Release.

Posted on by Nancy Atkinson

Hubble Provides Evidence for ‘Double Degenerate Progenitor’ Supernova

Supernova remnant SNR 0509-67.5. Supernovae provided the heavier elements in the Sun. Image credit: NASA/ESA/CXC
Supernova remnant SNR 0509-67.5. Supernovae provided the heavier elements in the Sun. Image credit: NASA/ESA/CXC

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What happened 400 years ago to create this stunningly beautiful supernova remnant – and were there two culprits or just one? This Hubble Space Telescope view of a Type Ia-created remnant has helped astronomers solve a longstanding mystery on the type of stars that cause some supernovae, known as a progenitor.

“Up until this point we haven’t really known where this type of supernova came from, despite studying them for decades,” said Ashley Pagnotta of Louisiana State University, speaking at a press briefing at the American Astronomical Society meeting on Wednesday. “But we now can say we have the first definitive identification of a Type 1a progenitor, and we know this one must have had a double degenerate progenitor – it is the only option.”

This supernova remnant that has a telephone number-like name of SNR 0509-67.5, lies 170,000 light-years away in the Large Magellanic Cloud galaxy.

Astronomers have long suspected that two stars were responsible for the explosion – as is the case with most type 1a supernovae — but weren’t sure what triggered the explosion. One explanation could be that it was caused by mass transfer from a companion star where a nearby star spills material onto a white dwarf companion, setting off a chain reaction that causes one of the most powerful explosions in the universe. This is known as the ‘single-degenerate’ path – which seems to be the most plausible, common and most preferred explanation for many Type 1a supernovae.

The other option is the collision of two white dwarfs, which is known as ‘double-degenerate, which seems to be the less common and not as widely accepted explanation for supernovae. To many astrophysicists, the merger scenario seemed to be less likely because too few double-white-dwarf systems appear to exist; indeed, there appear to be just handful that have been discovered so far.

The problem with SNR 0509-67.5 was that astronomers could not find any remnant of the companion star. That’s why the double degenerate scenario was considered, as in that case, there won’t be anything left as both white dwarfs are consumed in the explosion. In the case of a single progenitor, the non-white dwarf star will still be near the explosion site and will still look very much as it did before the explosion.

Therefore, a possible way to distinguish between the various progenitor models has been to look deep in the center of an old supernova remnant to search for the ex-companion star.

“We know Hubble has the sensitivity necessary to detect the faintest white dwarf remnants that could have caused such explosions,” said lead investigator Bradley Schaefer from LSU. “The logic here is the same as the famous quote from Sherlock Holmes: ‘when you have eliminated the impossible, whatever remains, however improbable, must be the truth.'”

In 2010, Schaefer and Pagnotta were preparing a proposal to look for any faint ex-companion stars in the center of four supernova remnants in the Large Magellanic Cloud when they saw an Astronomy Picture of the Day photo showing an image the Hubble Space Telescope had already had taken of one of their target remnants, SNR 0509-67.5.

(Note: the January 12, 2012 APOD image is of SNR 0509-67.5!)

Because the remnant appears as a nice symmetric shell or bubble, the geometric center can be determined accurately. In analyzing in more detail the central region, they found it to be completely empty of stars down to the limit of the faintest objects Hubble can detect in the photos. The young age also means that any surviving stars have not moved far from the site of the explosion. They were able to cross off the list all the possible single degenerate scenarios, and were left with the double degenerate model in which two white dwarfs collide.

“Since we can exclude all the possible single degenerates, we know it must be a double degenerate,” Pagnotta said. “The cause of SNR 0509-67.5 can be explained best by two tightly orbiting white dwarf stars spiraling closer and closer until they collided and exploded.”

Pagnotta also noted that this supernova is actually not a normal Type 1a supernova, but a subclass called 1991t, which is an extra bright supernova.

A paper in 2010 by Marat Gilfanov of the Max Planck Institute for Astrophysics indicated that perhaps many Type 1a supernova were caused by two white dwarf stars colliding, which was a surprise to many astronomers. Additionally, a review of the recent supernova SN 2011fe, which exploded in August of 2011, explores the possibility of the double degenerate progenitor. An open question remains whether these white dwarf mergers are the primary catalyst for Type Ia supernovae in spiral galaxies. Further studies are required to know if supernovae in spiral galaxies are caused by mergers or a mixture of the two processes.

Schaefer and Pagnotta plan to look at other supernova remnants in the Large Magellenic Cloud to further test their observations.

Pagnotta confirmed that anyone with an internet connection could have made this discovery, as all the Hubble images used were available publicly, and the use of the Hubble data was sparked by APOD.

Sources: Science Paper by Bradley E. Schaefer and Ashley Pagnotta (PDF document), HubbleSite, AAS press briefing

Posted on by Nancy Atkinson

A Star-Making Blob from the Cosmic Dawn

This image shows one of the most distant galaxies known, called GN-108036, dating back to 750 million years after the Big Bang that created our universe. Credit: NASA, ESA, JPL-Caltech, STScI, and the University of Tokyo

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Looking back in time with some of our best telescopes, astronomers have found one of the most distant and oldest galaxies. The big surprise about this blob-shaped galaxy, named GN-108036, is how exceptionally bright it is, even though its light has taken 12.9 billion years to reach us. This means that back in its heyday – which astronomers estimate at about 750 million years after the Big Bang — it was generating an exceptionally large amount of stars in the “cosmic dawn,” the early days of the Universe.

“The high rate of star formation found for GN-108036 implies that it was rapidly building up its mass some 750 million years after the Big Bang, when the Universe was only about five percent of its present age,” said Bahram Mobasher, from the University of California, Riverside. “This was therefore a likely ancestor of massive and evolved galaxies seen today.”


An international team of astronomers, led by Masami Ouchi of the University of Tokyo, Japan, first identified the remote galaxy after scanning a large patch of sky with the Subaru Telescope atop Mauna Kea in Hawaii. Its great distance was then confirmed with the W.M. Keck Observatory, also on Mauna Kea. Then, infrared observations from the Spitzer and Hubble space telescopes were crucial for measuring the galaxy’s star-formation activity.

“We checked our results on three different occasions over two years, and each time confirmed the previous measurement,” said Yoshiaki Ono, also from the of the University of Tokyo.

Astronomers were surprised to see such a large burst of star formation because the galaxy is so small and from such an early cosmic era. Back when galaxies were first forming, in the first few hundreds of millions of years after the Big Bang, they were much smaller than they are today, having yet to bulk up in mass.

The team says the galaxy’s star production rate is equivalent to about 100 suns per year. For reference, our Milky Way galaxy is about five times larger and 100 times more massive than GN-108036, but makes roughly 30 times fewer stars per year.

Astronomers refer to the object’s distance by a number called its “redshift,” which relates to how much its light has stretched to longer, redder wavelengths due to the expansion of the universe. Objects with larger redshifts are farther away and are seen further back in time. GN-108036 has a redshift of 7.2. Only a handful of galaxies have confirmed redshifts greater than 7, and only two of these have been reported to be more distant than GN-108036.

About 380,000 years after the Big Bang, a decrease in the temperature of the Universe caused hydrogen atoms to permeate the cosmos and form a thick fog that was opaque to ultraviolet light, creating what astronomers call the cosmic dark ages.

“It ended when gas clouds of neutral hydrogen collapsed to generate stars, forming the first galaxies, which probably radiated high-energy photons and reionized the Universe,” Mobasher said. “Vigorous galaxies like GN-108036 may well have contributed to the reionization process, which is responsible for the transparency of the Universe today.”

“The discovery is surprising because previous surveys had not found galaxies this bright so early in the history of the universe,” said Mark Dickinson of the National Optical Astronomy Observatory in Tucson, Ariz. “Perhaps those surveys were just too small to find galaxies like GN-108036. It may be a special, rare object that we just happened to catch during an extreme burst of star formation.”

Sources: Science Paper by: Y. Ono et al., Subaru , Spitzer Hubble

Posted on by Nancy Atkinson

Hubble’s Snow Angel

The bipolar star-forming region, called Sharpless 2-106, looks like a soaring, celestial snow angel. The outstretched “wings” of the nebula record the contrasting imprint of heat and motion against the backdrop of a colder medium. Twin lobes of super-hot gas, glowing blue in this image, stretch outward from the central star. This hot gas creates the “wings” of our angel. A ring of dust and gas orbiting the star acts like a belt, cinching the expanding nebula into an “hourglass” shape. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

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If you need a little help getting into the holiday spirit, the Hubble Space Telescope is here to assist. This gorgeous new image shows a bipolar star-forming region, called Sharpless 2-106, (S106 for short) which looks like a soaring, celestial snow angel. The outstretched “wings” of the nebula are actually the contrasting imprint of heat and motion against the backdrop of a colder medium. Twin lobes of super-hot gas, glowing blue in this image, stretch outward from the central star, forming the wings.

Hubble snapped this image in February 2011, using the Wide Field Camera 3. Visible narrow-band filters that isolate the hydrogen gas were combined with near-infrared filters that show structure in the cooler gas and dust.

A massive, young star, IRS 4 (Infrared Source 4), is responsible for all the activity here. A ring of dust and gas orbiting the star acts like a belt, cinching the expanding nebula into an hourglass shape. Hubble’s sharp resolution reveals ripples and ridges in the gas as it interacts with the cooler interstellar medium.

Although you can’t see them here, detailed studies of the nebula have also uncovered several hundred brown dwarfs. At purely infrared wavelengths, more than 600 of these sub-stellar objects appear. These “failed” stars weigh less than a tenth of the Sun. Because of their low mass, they cannot produce energy through nuclear fusion like the Sun does.

Posted on by Tammy Plotner

Supernova Candidate Stars May Signal “Impending Doom”

This Large Binocular Telescope image below of the Whirlpool Galaxy, otherwise known as M51, is part of a new galaxy survey by Ohio State University, where astronomers are searching for signs that stars are about to go supernova. The insets show one particular binary star system before (left) and after (right) one of its stars went supernova. Image by Dorota Szczygiel, courtesy of Ohio State University.

[/caption] This past year has given both backyard and professional astronomers a rare treat – a very visible supernova event. Hosted in the Whirlpool Galaxy (M51), these stellar death throes may have been clued to us by a rather ordinary binary star system. In a recent study done by researchers at Ohio State University, a galaxy survey may have captured evidence of a “stellar signal” just before it went supernova!

Employing the Large Binocular Telescope located in Arizona, the OSU team was undertaking a survey of 25 galaxies for stars that changed their magnitude in usual ways. Their goal was to find a star just before it ended its life – a three-year undertaking. As luck would have it, a binary star system located in M51 produced just the results they were looking for. One star dropped amplitude just a short period of time before the other exploded. While the probability factor of them getting the exact star might be slim, chances are still good they caught its brighter partner. Despite that, principal investigator Christopher Kochanek, professor of astronomy at Ohio State and the Ohio Eminent Scholar in Observational Cosmology, remains optimistic as their results prove a theory.

“Our underlying goal is to look for any kind of signature behavior that will enable us to identify stars before they explode,” he said. “It’s a speculative goal at this point, but at least now we know that it’s possible.”

“Maybe stars give off a clear signal of impending doom, maybe they don’t,” said study co-author Krzystof Stanek, professor of astronomy at Ohio State, “But we’ll learn something new about dying stars no matter the outcome.”

Postdoctoral researcher Dorota Szczygiel, the leader of the supernova study tells us why the galaxy survey remains paramount.

“The odds are extremely low that we would just happen to be observing a star for several years before it went supernova. We would have to be extremely lucky,” she said. “With this galaxy survey, we’re making our own luck. We’re studying all the variable stars in 25 galaxies, so that when one of them happens go supernova, we’ve already compiled data on it.”

On May 31, 2011, the whole astronomy world was abuzz when SN2011dh gave both amateurs and professionals a real thrill as an easily observable event. As luck would have it, it was a binary star system being studied by the OSU team, and consisted of both a blue and red star. At this point, the astronomers surmise the red star was the one that dimmed significantly over the three-year period while the blue one blew its top. When reviewing the LBT data, the Ohio team found that when compared with Hubble images, the red star dimmed at about 10% over the final three-year period at an estimated 3% per previous years. As a curiosity, the researchers surmise the red star may have actually survived the supernova event.

“After the light from the explosion fades away, we should be able to see the companion that did not explode,” Szczygiel said.

As the team continues to collect valuable information, they estimate they could also detect another candidate set of stars at a rate of about one per year. There is also a strong possibility these detections could act as a type of test bed to predict future supernova events… looking for signals of impending doom. However, according to the news release, the Sun won’t be one to bother with.

“There’ll be no supernova for the Sun – it’ll just fizzle out,” Kochanek said. “But that’s okay – you don’t want to live around an exciting star.”

Original Story Source: Ohio State Research News.

Posted on by Tammy Plotner

NGC 1846 – Hubble Reveals Peculiar Life And Death Of A Stellar Population

NASA's Hubble Finds Stellar Life and Death in a Globular Cluster - Credit: HST/NASA

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About 160,000 light years away in the direction of southern constellation Doradus, sits a globular cluster. It’s not a new target for the Hubble Space Telescope, but it has had a lot to say for itself over the last twelve years. It’s actually part of the Large Magellanic Cloud, but it’s no ordinary ball of stars. When it comes to age, this particular region is mighty complex…

In a 34 minute exposure taken almost a half dozen years ago, the Hubble snapped both life and death combined in an area where all stars were once assumed to be the same age. Globular clusters, as we know, are spherical collections of stars bound by gravity which orbit the halo of many galaxies. At one time, astronomers assumed their member stars were all the same age – forming into their own groups at around the same time the parent galaxy formed. But now, evidence points toward these balls of stars as having their own agenda – and may have evolved independently over the course of several hundreds of million years. What’s more, we’re beginning to learn that globular cluster formation may differ from galaxy to galaxy, too. Why? Chances are they may have encountered additional molecular clouds during their travels which may have triggered another round of star formation.

“An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations.” says Giampaolo Piotto of the University of Padova, Italy. “These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. Multiple stellar populations have been identified in Galactic and Magellanic Cloud clusters.”

However, it’s not the individual stars which make this Hubble image such a curiosity, it’s the revelation of a planetary nebula. This means a huge disparity in the member star’s ages…. one of up to 300 million years. Is it possible that the shell and remains of this dead star is a line-of-sight phenomenon, or is it truly a cluster member?

“We report on Hubble Space Telescope/ACS photometry of the rich intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud, which clearly reveals the presence of a double main-sequence turn-off in this object. Despite this, the main-sequence, subgiant branch and red giant branch are all narrow and well defined, and the red clump is compact.” says A. D. Mackey and P. Broby Nielsen. ” We examine the spatial distribution of turn-off stars and demonstrate that all belong to NGC 1846 rather than to any field star population. In addition, the spatial distributions of the two sets of turn-off stars may exhibit different central concentrations and some asymmetries. By fitting isochrones, we show that the properties of the colour–magnitude diagram can be explained if there are two stellar populations of equivalent metal abundance in NGC 1846, differing in age by around 300 million years.”

So what’s wrong with the picture? Apparently nothing. The findings have been studied and studied again for errors and even “contamination” by field stars in relation to NGC1846’s main sequence turn off. It’s simply a bit of a cosmic riddle just waiting for an explanation.

“We propose that the observed properties of NGC 1846 can be explained if this object originated via the tidal capture of two star clusters formed separately in a star cluster group in a single giant molecular cloud.” concludes Mackey and Nielson. “This scenario accounts naturally for the age difference and uniform metallicity of the two member populations, as well as the differences in their spatial distributions.”

Original Story Source: NASA’s Hubble Finds Stellar Life and Death in a Globular Cluster. For Further Reading: A double main-sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud, Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. I. NGC 1846 and its Wide Main-Sequence Turnoff and Multiple stellar populations in three rich Large Magellanic Cloud star clusters.

Posted on by Tammy Plotner

Grunsfeld May Lead NASA Science Division

John Grunsfeld was one of the astronauts involved in fixing the Hubble Space Telescope. Credit: NASA
John Grunsfeld was one of the astronauts involved in fixing the Hubble Space Telescope. Credit: NASA

[/caption]The current buzz amongst those in the know say that astrophysicist/astronaut, John Grunsfeld, has been chosen to lead NASA’s science mission directorate. Self-confessed “Hubble Hugger” and telescope repair man may very well become NASA associate administrator in September, according to a news article in Nature. As current deputy director of the Space Telescope Science Institute in Baltimore, Maryland, Grunsfeld will be replacing the resigning Ed Weiler.

“John is a very capable guy,” Weiler was quoted by writer Eric Hand in Nature. “He knows both the human and robotic sides. He’s a very solid citizen.”

However, NASA spokesman Trent Perrotto says no appointment has yet been made official.

Nature reports that the five-time shuttle astronaut could likely be the top choice of NASA administrator Charles Bolden, also a former shuttle pilot, and may display just a bit of favoritism towards fellow astronauts. “Clearly, he’s Charlie’s pick,” says one person with knowledge of the selection.

But Nature quotes another science source that Grunsfeld might not be the right pick. Apparently he/she believes that NASA-backed scientists who aren’t part of the astronomy field shouldn’t be a prime candidate. “His entire reputation is based on fixing space telescopes,” says the scientist. “I think it will be a real tough slog for him.”

Read more in Nature News.

And we’ll keep you posted of any official announcements.

Original Story Source: Nature News.

Posted on by Tammy Plotner

Do Galaxies Recycle Their Material?

Distant quasars shine through the gas-rich "fog" of hot plasma encircling galaxies. At ultraviolet wavelengths, Hubble's Cosmic Origins Spectrograph (COS) is sensitive to absorption from many ionized heavy elements, such as nitrogen, oxygen, and neon. COS's high sensitivity allows many galaxies that happen to lie in front of the much more distant quasars. The ionized heavy elements serve as proxies for estimating how much mass is in a galaxy's halo. (Credit: NASA; ESA; A. Feild, STScI)

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It’s a great question that’s now been validated by the Hubble Space Telescope. Recent observations have shown how galaxies are able to recycle huge amounts of hydrogen gas and heavy elements within themselves. In a process which begins at initial star formation and lasts for billions of years, galaxies renew their own energy sources.

Thanks to the HST’s Cosmic Origins Spectrograph (COS), scientists have now been able to investigate the Milky Way’s halo region along with forty other galaxies. The combined data includes instruments from large ground-based telescopes in Hawaii, Arizona and Chile whose goal was determine galaxy properties. In this colorful instance, the shape and spectra of each individual galaxy would appear to be influenced by gas flow through the halo in a type of “gas-recycling phenomenon”. The results are being published in three papers in the November 18 issue of Science magazine. The leaders of the three studies are Nicolas Lehner of the University of Notre Dame in South Bend, Ind.; Jason Tumlinson of the Space Telescope Science Institute in Baltimore, Md.; and Todd Tripp of the University of Massachusetts at Amherst.

The focus of the research centered on distant stars whose spectra illuminated influxing gas clouds as they pass through the galactic halo. This is the basis of continual star formation, where huge pockets of hydrogen contain enough fuel to ignite a hundred million stars. But not all of this gas is just “there”. A substantial portion is recycled by both novae and supernovae events – as well as star formation itself. It not only creates, but “replenishes”.

The color and shape of a galaxy is largely controlled by gas flowing through an extended halo around it. All modern simulations of galaxy formation find that they cannot explain the observed properties of galaxies without modeling the complex accretion and "feedback" processes by which galaxies acquire gas and then later expel it after chemical processing by stars. Hubble spectroscopic observations show that galaxies like our Milky Way recycle gas while galaxies undergoing a rapid starburst of activity will lose gas into intergalactic space and become "red and dead." (Credit: NASA; ESA; A. Feild, STScI)

However, this process isn’t unique to the Milky Way. Hubble’s COS observations have recorded these recycling halos around energetic star-forming galaxies, too. These heavy metal halos are reaching out to distances of up to 450,000 light years outside the visible portions of their galactic disks. To capture such far-reaching evidence of galactic recycling wasn’t an expected result. According to the Hubble Press Release, COS measured 10 million solar masses of oxygen in a galaxy’s halo, which corresponds to about one billion solar masses of gas – as much as in the entire space between stars in a galaxy’s disk.

So what did the research find and how was it done? In galaxies with rapid star formation, the gases are expelled outward at speed of up to two million miles per hour – fast enough to be ejected to the point of no return – and with it goes mass. This confirms the theories of how a spiral galaxy could eventually evolve into an elliptical. Since the light from this hot plasma isn’t within the visible spectrum, the COS used quasars to reveal the spectral properties of the halo gases. Its extremely sensitive equipment was able to detect the presence of heavy elements, such as nitrogen, oxygen, and neon – indicators of mass of a galaxy’s halo.

So what happens when a galaxy isn’t “green”? According to these new observations, galaxies which have ceased star formation no longer have gas. Apparently, once the recycling process stops, stars will only continue to form for as long as they have fuel. And once it’s gone?

It’s gone forever…

Original Story Source: Hubble Space Telescope News Release.

Posted on by Nancy Atkinson

Live Webcast from American Museum of Natural History Today: Beyond Planet Earth

The American Museum of Natural History in New York will soon be opening up a new exhibition called “Beyond Planet Earth: The Future of Space Exploration,” and they are live-streaming a special public program at 12 Noon EST (17:00 UT), that includes NASA astronauts Mike Massimino and John Grunsfeld, crew members on mission STS-125 to repair the Hubble Space Telescope, and is hosted by Hayden Planetarium Director Neil deGrasse Tyson and Curator Michael Shara.

The discussion will focus on themes from Beyond Planet Earth, the STS-125 mission, and the temporary laser art installation From The Distant Past. For more information see the AMNH website, and watch a teaser video of “Beyond Planet Earth” below.

Continue reading “Live Webcast from American Museum of Natural History Today: Beyond Planet Earth”

Posted on by Tammy Plotner

Hubble Telescope Directly Observes Quasar Accretion Disc Surrounding Black Hole

A team of scientists has used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc — a brightly glowing disc of matter that is slowly being sucked into its galaxy’s central black hole. Their study makes use of a novel technique that uses gravitational lensing to give an immense boost to the power of the telescope. The incredible precision of the method has allowed astronomers to directly measure the disc’s size and plot the temperature across different parts of the disc. Image credit: NASA, ESA, J.A. Munoz (University of Valencia)

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Thanks to the magic of the NASA/ESA Hubble Space Telescope, a team of international astronomers have made an incredible observation – a quasar accretion disc surrounding a black hole. By employing a technique known as gravitation lensing, the researchers have been able to get an accurate size measurement and spectral data. While you might not think this exciting at first, know that this type of observation is akin to spotting individual grains of sand on the Moon!

Of course, we know we can’t see a black hole – but we’ve learned a lot about them with time. One of their properties is a bright, visible phenomenon called a quasar. These glowing discs of matter are engaged in orbit around the black hole, much like a coil on an electric stove. As energy is applied, the “coil” heats up and unleashes bright radiation.

“A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away. This means their apparent size when viewed from Earth is so small that we will probably never have a telescope powerful enough to see their structure directly,” explains Jose Munoz, the lead scientist in this study.

Because of the diminutive size of the quasar, most of our understanding of how they work has been based on theory… but great minds have found a way to directly observe their effects. By employing the gravity of stars in an intervening galaxy like a scanning microscope, astronomers have been able to observe the quasar’s light as the stars move. While most of these types of features would be too small to see, the gravitation lensing effect ramps up the strength of the quasar’s light and allows study of the spectra as it cruises across the accretion disc.

This diagram shows how Hubble is able to observe a quasar, a glowing disc of matter around a distant black hole, even though the black hole would ordinarily be too far away to see clearly. Credit: NASA and ESA

By observing a group of gravitationally lensed quasars, the team was able to paint a vivid color portrait of the activity. They were able to pick out small changes between single images and spectral shifts over a period of time. What causes these kaleidoscopic variances? For the most part, it’s the different properties in the gases and dust of the lensing galaxies. Because they travel at different angles to the quasar’s light, scientists were even able to distinguish extinction laws at work.

But there was something special about one of the quasars. Says the Hubble Team, “There were clear signs that stars in the intervening galaxy were passing through the path of the light from the quasar. Just as the gravitational effect due to the whole intervening galaxy can bend and amplify the quasar’s light, so can that of the stars within the intervening galaxy subtly bend and amplify the light from different parts of the accretion disc as they pass through the path of the quasar’s light.”

By documenting these color changes, the team could build a profile of the accretion disc. Unlike our Earthly electric stove coil which glows red as it heats up, the accretion disc of a black hole turns blue as it gets closer to the event horizon. By measuring the blue hue, the team was able to measure the disc diameter and the various tints gave them an indicator of distances from its center. In this case, they found that the disc is between four and eleven light-days across (approximately 100 to 300 billion kilometres). Of course, these are only rough estimates, but considering just how far away we’re looking at such a small object gives these types of observations great potential for future studies… and even improvements on accuracy.

“This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone,” says Munoz. “Quasars’ physical properties are not yet well understood. This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects.”

Original Story Source: ESA/Hubble News Release. For Further Reading: A Study of Gravitational Lens Chromaticity With the Hubble Space Telescope.