Posted on by Ryan Anderson

WISE Mission Completes All-sky Infrared Survey

This view of the Pleiades star cluster is a composite of hundreds of WISE images, a tiny fraction of all those collected to complete the full-sky survey. Image credit: NASA/JPL-Caltech/UCLA

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If you take a lot of digital pictures, you’re probably familiar with the frustration of keeping track of dozens of files, and always running out of hard drive space to store them. Well, the scientists and engineers on NASA’s Wide-field Infrared Survey Explorer (WISE) mission have no pity for you. Their spacecraft just finished photographing the entire sky in exquisite detail: a total of 1.3 million photos.

“The eyes of WISE have not blinked since launch,” said William Irace, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Both our telescope and spacecraft have performed flawlessly and have imaged every corner of our universe, just as we planned.”

WISE surveys the sky in strips as it orbits the earth. It takes six months of constant observing to map the entire sky. By pointing at every part of the sky, astronomical surveys deliver excellent data covering both well-known objects and those that have never been seen before.

“WISE is filling in the blanks on the infrared properties of everything in the universe from nearby asteroids to distant quasars,” said Peter Eisenhardt of JPL, project scientist for WISE. “But the most exciting discoveries may well be objects we haven’t yet imagined exist.”

One example of a well-known object seen in new light by WISE is the Pleiades cluster: a group of young blue stars shrouded by dust that the cluster is currently passing through. In WISE’s false-color infrared vision, the hot stars look blue but the cooler dust clouds give off longer wavelengths of infrared light, causing them to glow in shades of yellow and green.

The WISE survey is particularly significant because such a wide range of objects in the universe are visible in infrared light. Giant molecular clouds glow in infrared light, as do brown dwarfs – objects that are bigger than planets but smaller than true stars. WISE can also see ultra-bright, extremely distant galaxies whose visible light has been stretched into the infrared by the expansion of the universe during its multi-billion-year journey.

The recently completed WISE survey also observed 100,000 asteroids in our solar system, many of which had never been seen before. 90 of the newly discovered asteroids are near-earth objects, whose orbits cross our own, making them potentially dangerous but also potential targets for future mission.

You might think that 1.3 million pictures would be plenty, but WISE will keep mapping the sky for another three months, covering half of the sky again and allowing astronomers to search for changes. The mission will end when the spacecraft’s solid hydrogen coolant finally runs out and the infrared detectors warm up (they don’t work as well when they are warm enough to emit the same wavelengths of infrared light that they are meant to detect).

But even as the telescope warms up, the astronomers on the WISE team will just be getting warmed up too. With nearly two million images, they will be busy making new discoveries for years to come.

Posted on by Nancy Atkinson

Zoom into a New VISTA of the Sculptor Galaxy

VISTA’s infrared view of the Sculptor Galaxy (NGC 253). Credit: ESO

The new VISTA telescope at the Paranal Observatory in Chile (the Visible and Infrared Survey Telescope for Astronomy) has captured a great new image of the Sculptor Galaxy (NGC 253), and this video allows you to zoom in for a closer look. The sequence starts with a wide view of the southern sky far from the Milky Way. Only a few stars are visible, but then VISTA brings us in closer where the view shifts to the very detailed new infrared image of NGC 253 provided by the new telescope at Paranal. By observing in infrared light VISTA’s view is less affected by dust and reveals a myriad of cooler stars as well as a prominent bar of stars across the central region. The VISTA image provides much new information on the history and development of the galaxy. See the still image below.

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The Sculptor Galaxy (NGC 253) lies in the constellation of the same name and is one of the brightest galaxies in the sky. It is prominent enough to be seen with good binoculars and was discovered by Caroline Herschel from England in 1783. NGC 253 is a spiral galaxy that lies about 13 million light-years away. It is the brightest member of a small collection of galaxies called the Sculptor Group, one of the closest such groupings to our own Local Group of galaxies. Part of its visual prominence comes from its status as a starburst galaxy, one in the throes of rapid star formation. NGC 253 is also very dusty, which obscures the view of many parts of the galaxy. Seen from Earth, the galaxy is almost edge on, with the spiral arms clearly visible in the outer parts, along with a bright core at its center.

Learn more about this image and the VISTA telescope at the ESO website.

Posted on by Nancy Atkinson

Galaxies Like Grains of Sand in New Herschel Image

Alternate Universe
Image of the distant Universe as seen by Herschel’s SPIRE instrument Credit: ESA / SPIRE and HerMES consortia

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Wow. Just wow. Each of the colored dots in this new image from the Herschel telescope is a galaxy containing billions of stars. These are distant luminous infrared galaxies, and appear as they did 10–12 billion years ago, packed together like grains of sand on a beach, forming large clusters of galaxies by the force of their mutual gravity.

“These amazing new results from Herschel are just a taste of things to come, as Herschel continues to unlock the secrets of the early stages of star birth and galaxy formation in our Universe,” said Dr. David Parker, Director of Space Science and Exploration at the UK Space Agency.

The galaxies are color coded in blue, green, and red to represent the three wavebands used for Herschel’s observation. Those appearing in white have equal intensity in all three bands and are the ones forming the most stars. The galaxies shown in red are likely to be the most distant, appearing as they did around 12 billion years ago.

For more than a decade, astronomers have puzzled over strangely bright galaxies in the distant Universe. These luminous infrared galaxies appear to be creating stars at such phenomenal rates that they defy conventional theories of galaxy formation.

Now ESA’s Herschel infrared space observatory, with its ability for very sensitive mapping over wide areas, has seen thousands of these galaxies and pinpointed their locations, showing for the first time just how closely they are sardined together.

The mottled effect in the image gives away this clustering. All the indications are that these galaxies are busy crashing into one another, and forming large quantities of stars as a result of these violent encounters.
This image is part of the Herschel Multi-tiered Extragalactic Survey (HerMES) Key Project, which studies the evolution of galaxies in the distant, ancient Universe. The project uses the SPIRE (Spectral and Photometric Imaging REceiver) instrument on Herschel and has been surveying large areas of the sky, currently totalling 15 square degrees, or around 60 times the apparent size of the Full Moon.

This particular image was taken in a region of space called the Lockman hole, which allows a clear line of sight out into the distant Universe. This ‘hole’ is located in the familiar northern constellation of Ursa Major, The Great Bear.

HerMES will continue to collect more images, over larger areas of the sky in order to build up a more complete picture of how galaxies have evolved and interacted over the past 12 billion years.

Sources: UKSA, Online Showcase of Herschel Images

Posted on by Nancy Atkinson

Hail to His Spiralness, M83

M83. Credit: ESO/M. Gieles. Acknowledgement: Mischa Schirmer

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ESO released a beautiful image today of M83, a classic spiral galaxy. The image was taken by the HAWK-I instrument on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. The picture shows the galaxy in infrared light and the combination of the huge mirror of the VLT, the large field of view and great sensitivity of the HAWK –I and the superb observing conditions at ESO’s Paranal Observatory makes this one of the sharpest and most detailed pictures of Messier 83 ever taken from the ground. M83 is perhaps a mirror to how our own Milky Way galaxy looks, could we step outside and take a look.

Messier 83 is located about 15 million light-years away in the constellation of Hydra. It is famous for its many supernovae: over the last century, six supernovae have been observed in Messier 83 — a record number that is matched by only one other galaxy. Even without supernovae, Messier 83 is one of the brightest nearby galaxies, visible using just binoculars.

Check out this article by our resident astronomer Tammy Plotner to find out how you can spot M83 in the night sky.

Source: ESO

Posted on by Nancy Atkinson

New Image Reveals Thousands of Galaxies in Abell 315

Galaxy Cluster Abell 315 as seen by ESO's 2.2 meter telescope at La Silla. Credit: ESO/J. Dietrich

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In an image akin to the Hubble Deep Field, ESO’s La Silla Observatory in Chile stared at a patch of sky about as big as a full Moon and observed thousands of distant galaxies. The Wide Field Imager on ESO’s 2.2 meter telescope zeroed in on a large group of galaxies that are part of the massive galaxy cluster known as Abell 315. But there’s more in this image—including relatively close asteroids that show up as blue, green or red trails, which lie in the main asteroid belt, located between the orbits of Mars and Jupiter. Also, invisible dark matter is revealed in this image through its gravitational effects, noticeably visible on this galaxy cluster.

Of course, not all the galaxies seen here are the same distance from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos if you zoom in on this larger image, especially in the upper part of the image. The more distant galaxies appear just like faint of blobs — their light has traveled through the Universe for eight billion years or more before reaching Earth.

The concentration of about a hundred yellowish galaxies is the Abell 315 galaxy cluster. The cluster is located in the constellation of Cetus (the Whale).

The galaxies in these clusters contribute to only ten percent of the mass, with hot gas in between galaxies accounting for another ten percent. The remaining 80 percent is made of dark matter that lies in between the galaxies.

We know the dark matter is there because of its effects: the enormous mass of a galaxy cluster acts on the light from galaxies behind the cluster like a cosmic magnifying glass, bending the trajectory of the light and thus making the galaxies appear slightly distorted. By observing and analyzing the twisted shapes of these background galaxies, astronomers can infer the total mass of the cluster responsible for the distortion, even when this mass is mostly invisible. However, this effect is usually tiny, and it is necessary to measure it over a huge number of galaxies to obtain significant results. In the case of Abell 315, the shapes of almost 10,000 faint galaxies in this image were studied in order to estimate the total mass of the cluster, which amounts to over a hundred thousand billion times the mass of our Sun.

For more information see the ESO release and additional images.

Posted on by Nancy Atkinson

Hubble Captures Distorted Beauty of M66

M 66. Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Davide De Martin and Robert Gendler

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This isn’t your basic spiral galaxy, but perhaps it used to be! Hubble’s Advanced Camera for Surveys has captured this beautiful view of the biggest child of the Leo Triplet, M66. Its asymmetric spiral arms and an apparently displaced core was mostly likely caused by the gravitational pull of the other two members of the trio. Talk about sibling rivalry!

M66, is located at a distance of about 35 million light-years in the constellation of Leo. Together with Messier 65 and NGC 3628, Messier 66 is one third of the Leo Triplet, a trio of interacting spiral galaxies, part of the larger Messier 66 group. While M66 is the biggest — it is about 100,000 light-years across — the gravitational influence from the two neighboring galaxies have distorted the one orderly spiral arms, making them appear to rise above the central core.

The striking dust lanes and bright star clusters along the spiral arm — pictured in the blue and pinkish regions of the image — are key tools for astronomers since they are used as indicators of how the parent galaxies assembled over time.

Messier 66 boasts a remarkable record of supernovae explosions. The spiral galaxy has hosted three supernovae since 1989, the latest one occurring in 2009. A supernova is a stellar explosion that may momentarily outshine its entire host galaxy. It then fades away over a period lasting several weeks or months. During its very short life the supernova radiates as much energy as the Sun would radiate over a period of about 10 billion years.

Source: European Hubble Space Telescope webpage

Posted on by Jean Tate

This Week’s astro-ph Preprints: Jean Tate’s Best Pick

Examples of ring objects (Mizuno et al./Spitzer)

It goes by the super-catchy (not!) title “A Catalog of MIPSGAL Disk and Ring Sources”. I chose it, over 213 competitors, because it’s pure astronomy, and because it’s something you don’t need a PhD to be able to do, or even a BSc.

Oh, and also because Don Mizuno and co-authors may have found two, quite local, spiral galaxies that no one has ever seen before!

Some quick background: arXiv has been going for several years now, and provides preprints, on the web, of papers “in the fields of physics, mathematics, non-linear science, computer science, quantitative biology and statistics”. It’s owned, operated and funded by Cornell University. astro-ph is the collection of preprints classified as astro physics; the “recent” category in astro-ph is the new preprints submitted in the last week.

When I have any, one of my favorite spare-time activities is browsing astro-ph (Hey, I did say, in my profile, that I am hooked on astronomy!)

Briefly, what Mizuno and his co-authors did was get hold of some of the images from Spitzer (something that anyone can do, provided their internet connection has enough bandwidth), and eyeball them, looking for things which look like disks and rings. Having found over 400 of them, they did what the human brain does superbly well: they grouped them by similarity of appearance, and gave the groups names. They then checked out other images – from different parts of Spitzer’s archive, and from IRAS – and checked to see how many had already been cataloged.

And what did they find? Well, first, that most of the objects they found had not been cataloged before, and certainly not given definite classifications! Many, perhaps most, of the new objects are planetary nebulae, and their findings may help address a long-standing puzzle in this part of astronomy.

MGE314.2378+00.9793 (Mizuno et al./Spitzer)
MGE351.2381-00.0145 (Mizuno et al./Spitzer)

But they also may have found two local spiral galaxies, which had not been noticed before because they are obscured by the gas-and-dust clouds in the Milky Way plane. How cool is that!

Here’s the ‘credits’ section of the preprint: “This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA in part through an award issued by JPL/Caltech. This research made use of the SIMBAD database and the Vizier catalog access tool, operated by the Centre de Donnees Astronomique de Strasbourg. This research has also made use of NASA’s Astrophysics Data System Bibliographic Services.”

And here’s the preprint itself: arXiv:1002.4221 A Catalog of MIPSGAL Disk and Ring Sources; D.R. Mizuno(1), K. E. Kraemer(2), N. Flagey(3), N. Billot(4), S. Shenoy(5), R. Paladini(3), E. Ryan(6), A. Noriega-Crespo(3), S. J. Carey(3). ((1) Institute for Scientific Research, (2) Air Force Research Laboratory, (3) Spitzer Science Center, (4) NASA Herschel Science Center, (5) Ames Research Center, (6) University of Minnesota)

PS, going over the Astronomy Cast episode How to be Taken Seriously by Scientists is what motivated me to pick this preprint (however, I must tell you, in all honesty, that there are at least ten other preprints that are equally pickable).

Posted on by Nancy Atkinson

Double Hubble Sequence Shows Galaxies Go Spiral

This image created from data taken from both the NASA/ESA Hubble Space Telescope and the Sloan Digital Sky Survey demonstrates that the Hubble sequence six billion years ago was very different from the one that astronomers see today. Credit: NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano and F. Hammer (Observatoire de Paris)

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Galaxies come in all sorts of shapes. But in the past, the various galaxy shapes used to be more diverse and “peculiar” than they are now. Over time, according to a new study, galaxies tend to become spirals. “Six billion years ago, there were many more peculiar galaxies than now — a very surprising result,” said Rodney Delgado-Serrano, lead author of a new paper. “This means that in the last six billion years, these peculiar galaxies must have become normal spirals, giving us a more dramatic picture of the recent Universe than we had before.”

Using data from the Hubble Space Telescope and the Sloan Digital Sky Survey, a team of astronomers created the first demographic census of galaxy types at two different points in the Universe’s history, putting together two Hubble sequences from different eras that help explain how galaxies form. The results showed that the Hubble sequence six billion years ago was very different from the one that astronomers see today.

The top image represents the current — or local — universe, and the bottom image represents the make up of the distant galaxies (six billion years ago), showing a much larger fraction of peculiar galaxies. In sampling 116 local galaxies and 148 distant galaxies, the researchers found that more than half of the present-day spiral galaxies had so-called peculiar shapes only 6 billion years ago.

Edwin Hubble invented the Hubble Sequence, sometimes called the Hubble tuning-fork diagram. The diagram divides galaxies into three 3 broad classes based on their basic shapes: spiral, barred spiral, and elliptical.

“Our aim was to find a scenario that would connect the current picture of the Universe with the morphologies of distant, older galaxies — to find the right fit for this puzzling view of galaxy evolution,” said François Hammer of the Observatoire de Paris who led the team of astronomers.

The astronomers think that these peculiar galaxies did indeed become spirals through collisions and merging. This is contrary to the widely held opinion that galaxy mergers result in the formation of elliptical galaxies, but Hammer and his team propose a “spiral rebuilding” hypothesis, which suggests that peculiar galaxies affected by gas-rich mergers are slowly reborn as giant spirals with discs and central bulges.

Crashes between galaxies give rise to enormous new galaxies and, although it was commonly believed that galaxy mergers decreased significantly eight billion years ago, the new result implies that mergers were still occurring frequently after that time — up to as recently as four billion years ago.

Link to higher resolution version of the top image.

Papers:
Hammer, et al.
Delgado-Serrano et al.

Source: Space Telescope Institute

Posted on by Nancy Atkinson

Latest from Hubble: Star Formation Fizzling Out in Nearby Galaxy

NGC 2976.. NASA, ESA, and J. Dalcanton and B. Williams (University of Washington, Seattle)

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Most galaxies are throughout the universe are happenin’ places, with all sorts of raucous star formation going on. But for a nearby, small spiral galaxy, the star-making party is almost over. In this latest Hubble release, astronomers were surprised to find that star-formation activities in the outer regions of NGC 2976 are fizzling out, and any celebrating is confined to a few die-hard partygoers huddled in the galaxy’s inner region.

The reason? Well, the star birth began when another party-crashing galaxy interacted with NGC 2976. But that happened long ago, and now star formation in the galaxy is fizzling out in the outer parts as some of the gas was stripped away and the rest collapsed toward the center. With no gas left to fuel the party, more and more regions of the galaxy are going to sleep.

“Astronomers thought that grazing encounters between galaxies can cause the funneling of gas into a galaxy’s core, but these Hubble observations provide the clearest view of this phenomenon,” explains astronomer Benjamin Williams of the University of Washington in Seattle, who directed the Hubble study, which is part of the ACS Nearby Galaxy Survey Treasury (ANGST) program. “We are catching this galaxy at a very interesting time. Another 500 million years and the party will be over.”

NGC 2976 does not look like a typical spiral galaxy. It has a star-forming disk, but no obvious spiral pattern. Its gas is centrally concentrated, but it does not have a central bulge of stars. The galaxy resides on the fringe of the M81 group of galaxies, located about 12 million light-years away in the constellation Ursa Major.

“The galaxy looks weird because an interaction with the M81 group about a billion years ago stripped some gas from the outer parts of the galaxy, forcing the rest of the gas to rush toward the galaxy’s center, where it is has little organized spiral structure,” Williams says.

The galaxy’s relatively close distance to Earth allowed Hubble’s Advanced Camera for Surveys (ACS) to resolve hundreds of thousands of individual stars. What look like grains of sand in the image are actually individual stars. Studying the individual stars allowed astronomers to determine their color and brightness, which provided information about when they formed.

The image was taken over a period in late 2006 and early 2007.

“This type of observation is unique to Hubble,” Williams says. “If we had not been able to pick out individual stars, we would have known that the galaxy is weird, but we would not have dug up evidence for a significant gas rearrangement in the galaxy, which caused the stellar birth zone to shrink toward the galaxy’s center.”

Simulations predict that the same “gas-funneling” mechanism may trigger starbursts in the central regions of other dwarf galaxies that interact with larger neighbors. The trick to studying the effects of this process in detail, Williams says, is being able to resolve many individual stars in galaxies to create an accurate picture of their evolution.

Williams’ results will appear in the January 20, 2010 issue of The Astrophysical Journal.

Source: HubbleSite

Posted on by Nancy Atkinson

Dark Energy Model Explains ‘Hubble Sequence’ of Galaxies

A figure illustrating the Hubble sequence. On the left are elliptical galaxies, with their shapes ranging from spherical (E0) to elongated (E7). Type S0 is intermediate between elliptical and spiral galaxies. The upper right line of objects stretch from Sa (tightly wound spiral) to Sc (loosely wound spiral). The lower right line shows the barred spirals that range from the tightly wound SBa to loosely wound SBc types. Image: Ville Koistinen

Caption: A figure illustrating the Hubble sequence. Image: Ville Koistinen

One look at a Hubble Deep Field image reveals that galaxies come in all sorts of shapes and sizes. But why? Astronomers have been at a loss to explain the diversity of galaxy shapes seen in the Universe. But now, two astronomers have tracked the evolution of galaxies over thirteen billion years from the early Universe to the present day, helping to clarify the “Hubble Sequence,” a classification of galaxies developed by Edwin Hubble. Keys to their model include galaxy mergers and dark energy.

Dr. Andrew Benson of Caltech and Dr. Nick Devereux of Embry-Riddle University in Arizona Benson and Devereux combined data from the infrared Two Micron All Sky Survey (2MASS) with sophisticated computer model they developed, called GALFORM. The model reproduced the evolutionary history of the Universe over thirteen billion years. To their surprise, their computations reproduced not only the different galaxy shapes but also their relative numbers.

Caption: The image shows some of the galaxies generated by the computer model. The yellow objects are most distant and therefore appear as they were 13 billion years ago, whilst those closer are seen as they looked more recently. Image: A. Benson (University of Durham), NASA / STScI

“We were completely astonished that our model predicted both the abundance and diversity of galaxy types so precisely,” said Devereux. “It really boosts my confidence in the model,” Benson said.

The astronomers’ model is underpinned by and endorses the ‘Lambda Cold Dark Matter’ model of the Universe. Here ‘Lambda’ is the mysterious ‘dark energy’ component believed to make up about 72% of the cosmos, with cold dark matter making up another 23%. Just 4% of the Universe consists of the familiar visible or ‘baryonic’ matter that makes up the stars and planets of which galaxies are comprised.

Galaxies are thought to be embedded in very large haloes of dark matter and Benson and Devereux believe these to be crucial to their evolution. Their model suggests that the number of mergers between these haloes and their galaxies drives the final outcome – elliptical galaxies result from multiple mergers whereas disk galaxies have seen none at all. Our Milky Way galaxy’s barred spiral shape suggests it has seen a complex evolutionary history, with only a few minor collisions and at least one episode where the inner disk collapsed to form the large central bar.

In Hubble’s classification, there are three basic shapes: spiral, where arms of material wind out in a disk from a small central bulge; barred spiral, where the arms wind out in a disk from a larger bar of material; and elliptical, where the galaxy’s stars are distributed more evenly in a bulge without arms or disk. The different types clearly result from different evolutionary paths, which Benson and Devereux’s model now explains.

“These new findings set a clear direction for future research. Our goal now is to compare the model predictions with observations of more distant galaxies seen in images obtained with the Hubble and those of the soon to be launched James Webb Space Telescope (JWST)”, said Devereux.

Their results appear in the journal Monthly Notices of the Royal Astronomical Society.

Benson and Devereux’s paper.

Lead image complete caption: A figure illustrating the Hubble sequence. On the left are elliptical galaxies, with their shapes ranging from spherical (E0) to elongated (E7). Type S0 is intermediate between elliptical and spiral galaxies. The upper right line of objects stretch from Sa (tightly wound spiral) to Sc (loosely wound spiral). The lower right line shows the barred spirals that range from the tightly wound SBa to loosely wound SBc types. Image: Ville Koistinen

Source: RAS