Posted on by Nancy Atkinson

Spiral Galaxies Could Eat Dwarfs All Across the Universe

Stellar streams around the galaxy M 63. Credit: R. Jay Gabany (Blackbird Obs.) in collaboration with D. Martinez-Delgado (MPIA and IAC) et al.

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For years, astronomers have seen evidence that – at least in our own local neighborhood — spiral galaxies are consuming smaller dwarf galaxies. As they are digested, these dwarf galaxies are severely distorted, forming structures like strange, looping tendrils and stellar streams that surround the cannibalistic spirals. But now, for the first time, a new survey has detected such tell-tale structures in galaxies more distant than our immediate galactic neighborhood, providing evidence that this galactic cannibalism might take place on a universal scale. Remarkably, these cutting-edge results were obtained with small, amateur-sized telescopes.


Since 1997, astronomers have seen evidence that spirals in our local group of galaxies are swallowing dwarfs. In fact, our own Milky Way is currently in the process of eating the Canis Major dwarf galaxy and the Sagittarius dwarf galaxy. But the Local group with its three spiral galaxies and numerous dwarfs is much too small a sample to see whether this digestive process is happening elsewhere in the Universe. But an international group of researchers led by David Martínez-Delgado from the Max Planck Institute for Astronomy recently completed a survey of spiral galaxies at distances of up to 50 million light-years from Earth, discovering the tell-tale signs of spirals eating dwarfs.

For their observations, the researchers used small telescopes with apertures between 10 and 50 cm, equipped with commercially available CCD cameras. The telescopes are located at two private observatories — one in the US and one in Australia. They are robotic telescopes that can be controlled remotely.

During the “eating” process, when a spiral galaxy is approached by a much smaller companion, such as a dwarf galaxy, the larger galaxy’s uneven gravitational pull severely distorts the smaller star system. Over the course of a few billions of years, tendril-like structures develop that can be detected by sensitive observation. In one typical outcome, the smaller galaxy is transformed into an elongated “tidal stream” consisting of stars that, over the course of additional billions of years, will join the galaxy’s regular stellar inventory through a process of complete assimilation. The study shows that major tidal streams with masses between 1 and 5 percent of the galaxy’s total mass are quite common in spiral galaxies.

One of the galaxies in the survey, NGC 4651, sports a remarkable umbrella-like structure. It is composed of tidal star streams, the remnants of a smaller satellite galaxy which NGC 4651 has attracted and torn apart. This galaxy's distance from Earth is 35 million light-years.Credit: R. Jay Gabany (Blackbird Obs.) in collaboration with D. Martínez-Delgado (MPIA and IAC) et al.

Detailed simulations depicting the evolution of galaxies predict both tidal streams and a number of other distinct features that indicate mergers, such as giant debris clouds or jet-like features emerging from galactic discs. Interestingly, all these various features are indeed seen in the new observations – impressive evidence that current models of galaxy evolution are indeed on the right track.

Smaller satellite galaxies caught by a spiral galaxy are distorted into elongated structures consisting of stars, which are known as tidal streams, as shown in this artist's impression. Credit: Jon Lomberg

The ultra-deep images obtained by Delgado and his colleagues open the door to a new round of systematic galactic interaction studies. Next, with a more complete survey that is currently in progress, the researchers intend to subject the current models to more quantitative tests, checking whether current simulations make the correct predictions for the relative frequency of the different morphological features.

While larger telescopes have the undeniable edge in detecting very distant, but comparatively bright star systems such as active galaxies, this survey provides some of the deepest insight yet when it comes to detecting ordinary galaxies that are similar to our own cosmic home, the Milky Way. The results attest to the power of systematic work that is possible even with smaller instruments.

For more images see this page from the Max Planck Institute for Astronomy

*Note: Originally the lead image image was credited incorrectly, and is actually a product of R. Jay Gabany, an astrophotographer whose work has been featured quite often here on Universe Today. See more of his amazing handiwork at his website, Cosmotography.

Source: Max Planck Institute for Astronomy

Posted on by Jon Voisey

The Black Hole/Globular Cluster Correlation

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Often in astronomy, one observable property traces another property which may be more difficult to observe directly; X-ray activity on stars can be used to trace turbulent heating of the photosphere. CO is used to trace cold H2. Sometimes these correlations make sense. Activities in stars produce the X-ray emissions. Other times, the tracer seems distantly related at best.

This is the case of a newly discovered correlation between the mass of the central black hole of galaxies and the number of globular clusters they contain. What can this relationship teach astronomers? Why does it hold for some types of galaxies better than others? And where does it come from in the first place.

The mass of a galaxy’s super massive black hole (SMBH) is known to have a strong relationship between many features of their host galaxies. It has identified to follow the range of velocities of stars in the galaxy, the mass and luminosity of the bulge of spiral galaxies, and the total amount of dark matter in galaxies. Because dark matter in the halo of galaxies and the luminosity have also been known to correspond to the number of globular clusters, Andreas Burkert of the Max-Planck-Institute for Extraterrestrial Physics in Germany, and Scott Tremaine at Princeton wondered if they could cut out the middlemen of dark matter and luminosity and still maintain a strong correlation between the central SMBH and the number of globular clusters.

Their initial investigation involved only 13 galaxies, but a follow-up study by Gretchen and William Harris and submitted to the Monthly Notices of the Royal Astronomical Society, increased the number of galaxies included in the survey to 33. The results of these studies indicated that for elliptical galaxies, the SMBH-GC relationship is evident. However, for lenticular galaxies there was no clear correlation. While there appeared to be a trend for classical spirals, the small number of data points (4) would not provide a strong statistical case independently, but did appear to follow the trend established by the elliptical galaxies.

Although the correlation appeared strong in most cases, about 10% of the galaxies included in the larger surveys were clear outliers. This included the Milky Way which has a SMBH mass that falls significantly short of the expectation from cluster number. One source of error the authors of the original study suspect is that it is possible that, in some cases, objects identified as globular clusters may have been misidentified and in actuality, be the cores of tidally stripped dwarf galaxies. Regardless, the relationship as it stands presently, seems to be quite strong and is even more tightly defined than that of the correlation between that of the SMBH mass and velocity dispersion that implied the potential relationship in the first place. The reason for the discordance in lenticular galaxies has not yet been explained and no reasons have yet been postulated.

But what of the cause of this unusual relation? Both sets of authors suggest the connection lies in the formation of the objects. While distinct in most respects, both are fed by major merger events; Black holes gain mass by accreting gas and globular clusters are often formed from the resulting shocks and interactions. Additionally, the majority of both types of objects formed at high redshifts.

Sources:

A correlation between central supermassive black holes and the globular cluster systems of early-type galaxies

The Globular Cluster/Central Black Hole Connection in Galaxies

Posted on by Jon Voisey

Ultraluminous Gamma Ray Burst 080607 – A “Monster in the Dark”

Shedding Light on Dark Gamma Ray Bursts
Shedding Light on Dark Gamma Ray Bursts

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Gamma Ray Bursts (GRBs) are among the most energetic phenomena astronomers regularly observe. These events are triggered by massive explosions and a large amount of the energy if focused into narrow beams that sweep across the universe. These beams are so tightly concentrated that they can be seen across the visible universe and allow astronomers to probe the universe’s history. If such an event happened in our galaxy and we stood in the path of the beam, the effects would be pronounced and may lead to large extinctions. Yet one of the most energetic GRBs on record (GRB 080607) was shrouded in cloud of gas and dust dimming the blast by a factor of 20 – 200, depending on the wavelength.  Despite this strong veil, the GRB was still bright enough to be detected by small optical telescopes for over an hour. So what can this hidden monster tell astronomers about ancient galaxies and GRBs in general?

GRB 080607 was discovered on June 6, 2008 by the Swift satellite. Since GRBs are short lived events, searches for them are automated and upon detection, the Swift satellite immediately oriented itself towards the source. Other GRB hunting satellites quickly joined in and ground based observatories, including ROTSE-III and Keck made observations as well. This large collection of instruments allowed astronomers, led by D. A. Perley of UC Berkley, to develop a strong understanding of not just the GRB, but also the obscuring gas. Given that the host galaxy lies at a distance of over 12 billion light years, this has provided a unique probe into the nature of the environment of such distant galaxies.

One of the most surprising features was unusually strong absorption near 2175 °A. Although such absorption has been noticed in other galaxies, it has been rare in galaxies at such large cosmological distances. In the local universe, this feature seems to be most common in dynamically stable galaxies but tends to be “absent in more disturbed locations such as the SMC, nearby starburst galaxies” as well as some regions of the Milky Way which more turbulence is present. The team uses this feature to imply that the host galaxy was stable as well. Although this feature is familiar in nearby galaxies, observing it in this case makes it the furthest known example of this phenomenon. The precise cause of this feature is not yet known, although other studies have indicated “polycyclic aromatic hydrocarbons and graphite” are possible suspects.

Earlier studies of this event have shown other novel spectral features. A paper by Sheffer et al. notes that the spectrum also revealed molecular hydrogen. Again, such a feature is common in the local universe and many other galaxies, but never before has such an observation been made linked to a galaxy in which a GRB has occurred. Molecular hydrogen (as well as other molecular compounds) become disassociated at high temperatures like the ones in galaxies containing large amounts of star formation that would produce regions with large stars capable of triggering GRBs. With observations of one molecule in hand, this lead Sheffer’s team to suspect that there might be large amounts of other molecules, such as carbon monoxide (CO). This too was detected making yet another first for the odd environment of a GRB host.

This unusual environment may help to explain a class of GRBs known as “subluminous optical bursts” or “dark bursts” in which the optical component of the burst (especially the afterglow) is less bright than would be predicted by comparison to more traditional GRBs.

Sources:

Monster in the Dark: The Ultra Luminous GRB 080706 and its Dusty Environment

The Discovery of Vibrationally-Excited H2 In the Molecular Cloud Near GRB 080706

disassociated
Posted on by Nancy Atkinson

Colliding Galaxies Created the First Black Holes

The Antennae Galaxies in Collision Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

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How were the Universe’s first supermassive black holes formed? A new model of the evolution of galaxies and black holes show collisions show that colliding galaxies likely spawned black holes that formed about 13 billion years ago. The discovery fills in a missing chapter of our universe’s early history, and could help write the next chapter — in which scientists better understand how gravity and dark matter formed the universe as we know it.

Following the recent discovery that galaxies formed much earlier in the Universe’s history than previously thought, Stelios Kazantzidis from The Ohio State University and his team created new computer simulations that show the first-ever super-massive black holes were likely born when those early galaxies collided and merged together. This likely happened during the first few billion years after the Big Bang.

“Our results add a new milestone to the important realization of how structure forms in the universe,” Kazantzidis said.

Previously, astronomers thought galaxies evolved hierarchically, where gravity drew small bits of matter together first, and those small bits gradually came together to form larger structures.

But the the new models turn that notion on its head.

“Together with these other discoveries, our result shows that big structures — both galaxies and massive black holes — build up quickly in the history of the universe,” he said. “Amazingly, this is contrary to hierarchical structure formation. The paradox is resolved once one realizes that dark matter grows hierarchically, but ordinary matter doesn’t. The normal matter that makes up visible galaxies and super-massive black holes collapses more efficiently, and this was true also when the universe was very young, giving rise to anti-hierarchical formation of galaxies and black holes.”

So, that means that big galaxies and super-massive black holes come together quickly, and smaller bits like our own Milky Way galaxy — and the comparatively small black hole at its center — form more slowly. The galaxies that formed those first super-massive black holes are still around, Kazantzidis said.
The new simulations done on supercomputers were able to resolve features that were 100 times smaller, and revealed details in the heart of the merged galaxies on a scale of less than a light year.

Because of this, the astronomers were able to see two things: First, gas and dust in the center of the galaxies condensed to form a tight nuclear disk. Then the disk became unstable, and the gas and dust contracted again, to form an even denser cloud that eventually spawned a super-massive black hole.

The implications for cosmology are far-reaching, Kazantzidis said.

“For example, the standard idea — that a galaxy’s properties and the mass of its central black hole are related because the two grow in parallel — will have to be revised. In our model, the black hole grows much faster than the galaxy. So it could be that the black hole is not regulated at all by the growth of the galaxy. It could be that the galaxy is regulated by the growth of the black hole.”

In the image, the panel illustrates the complexity of dynamical evolution in a typical collision between two equal-mass disk galaxies. The simulation follows dark matter, stars, gas, and supermassive black holes, but only the gas component is visualized. Brighter colors indicate regions of higher gas density and the time corresponding to each snapshot is given by the labels. The first 10 panel images measure 100 kpc on a side, roughly five times the diameter of the visible part of the Milky Way galaxy. The next five panels represent successive zooms on the central region. The final frame shows the inner 300 pc of the nuclear region at the end of the simulation. Credit: Ohio State University

This new model could also help astronomers who are searching the skies for direct evidence of Einstein’s theory of general relativity: gravitational waves.

According to general relativity, any ancient galaxy mergers would have created massive gravitational waves — ripples in the space-time continuum — the remnants of which should still be visible today.

New gravitational wave detectors, such as NASA’s Laser Interferometer Space Antenna, were designed to detect these waves directly, and open a new window into astrophysical and physical phenomena that cannot be studied in other ways.

Scientists will need to know how super-massive black holes formed in the early universe and how they are distributed in space today in order interpret the results of those experiments. The new computer simulations should provide a clue.

See this link for videos of the models of galaxy collisions.

Source: Ohio State University

Posted on by Tammy Plotner

Astrophotography Spotlight – Centaurus A

“I’m on rhe outside… I’m lookin’ in.” And just who are we looking in at this time? None other than the familiar face of Centaurus A.. The stunning, turbulent dust lane is cloaked in the ethereal mist of living galaxy stuff – the result of a gravitationally hungry elliptical galaxy drawing a smaller companion spiral galaxy towards its demise. Like a spider waiting in the center of a web, the black hole at the heart of NGC 5128 takes no prisoners. Its complexity screams out to us in radio, X-ray, and gamma-ray energy. “I can see through you… See the real you.”

It waits in space some 10 to 11 million light years away. It’s the nearest active galaxy to Earth and contains a core black hole estimated to be a billion times the mass of our Sun. The result of Centaurus A’s merger event is so incredibly powerful that it may have even shifted the axis of the massive black hole from its expected orientation – an area not much larger than our own solar system. “The variability of the nucleus may represent the accretion of individual stellar or cloud remnants onto the black hole triggering renewed jet activity and fueling the radio source.” says F.P. Israel. “Details of these processes are not clear yet, but careful and frequent monitoring of Centaurus A at radio, X-ray and -ray wavelengths may provide important information. For instance, how does the nucleus drive the nuclear jets, and how are the relativistic nuclear jets transformed into the nonrelativistic inner jets? The circumnuclear disk does not seem capable of controlling the collimation of the nuclear jets, but its orientation exactly perpendicular to these jets, suggests that it is somehow connected with the collimating agent.”

Could it be the unique properties of Centaurus A originate from its cannibalizing an equally unique galaxy? If you examine the full size image by Ken Crawford you’ll find many background galaxies hidden amongst the stars. What we may very well be viewing is the early results of an giant elliptical merging with a much small spiral structure – creating a stunning halo. “When most people think of NGC 5128 (also known as Centaurus A) they see radio jets, central black holes, a very visible accretion disk and more. But these are “icing on the cake” of the underlying giant E galaxy.” says Gretchen Harris (University of Waterloo). “We now know the it has a fairly normal old halo system as seen in its globular clusters, planetary nebulae, and red giant stars. Its proximity makes NGC 5128 an ideal template for understanding the properties of large E galaxies in general.”

While science may consider Centaurus A to be a template, its tortured form makes it an incredible palette to the eye of the camera. Utilizing a RCOS 14.5″ Truss telescope and taking various exposures for nearly two hours, Ken has produced an image which reveals intricate details almost as fine as the 7 light-year resolution photos taken by the Hubble Space telescope.

Here you will see clumps of hot, young blue stars which have newly formed and the pink signature of star forming regions – as well as the release of gas which hasn’t conformed to the spin axis of the central black hole. Maybe two black holes duking it out? “This black hole is doing its own thing. Aside from receiving fresh fuel from a devoured galaxy, it may be oblivious to the rest of the galaxy and the collision,” said Ethan Schreier of the Space Telescope Science Institute. “”We have found a complicated situation of a disk within a disk within a disk, all pointing in different directions. It is not clear if the black hole was always present in the host galaxy or belonged to the spiral galaxy that fell into the core, or if it is the product of the merger of a pair of smaller black holes that lived in the two once-separate galaxies.”

Although the galactic merger may have began around 200 to 700 million years ago, the incredible arcs of multi-million degree gas remain in a 25,000 light-year diameter wobbling ring producing high energy jets. Given its size and location this ring might very well be a galaxy-sized shockwave – the million mile per hour outward ripples of an intense explosion which may have occurred some 10 million years ago. “We believe that most of these stars formed from the interaction of the jet with local concentrations of dust and gas.” says John Graham. “The brightest blue stars are presumably the youngest stars and tend to lie close to the X-ray jet. We suggest that the raw material for star formation is found in dust patches of small angular size in the area and that star formation is triggered by shocks initiated by the jet.”

Now I want you to take a closer look. What you are going to discover (highlighted by the small arrow) is a thin, blue smear of newly formed stars. It’s something you’d probably never notice unless it was pointed out to you.

What you are seeing is a thousand light year long band of scar tissue. A dead giveaway of a recent galactic absorption. Astronomers had previously noticed the arc now identified as a galactic merger remnant, but without recognizing its origin. “This adds a nice example in the local universe to the growing evidence that galaxy halos are built up from the accretion of dwarf satellite galaxies,” said Eric Peng, a graduate student in astronomy at Johns Hopkins University. “These halos are interesting partly because they’re hard to study, but also because time scales for things to happen in halos are very long, which means they may preserve conditions that reveal how a galaxy formed and evolved.”

But for now? “I’m on the outside… And I’m lookin’ in. I can see through you… See your true colors.”

Many thanks to Ken Crawford for his exquisite work which led to a wonderfully pleasant day of researching the ins and outs of a most remarkable galaxy!

Posted on by Nancy Atkinson

Giant Ultraviolet Rings Found Around Ancient Galaxies

Astronomers have found unexpected rings and arcs of ultraviolet light around a selection of galaxies, four of which are shown here as viewed by NASA's and the European Space Agency's Hubble Space Telescope. Image credit: NASA/ESA /JPL-Caltech/STScI/UCLA

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Title this ‘Zombie Galaxies’ or ‘Night of the Living Galaxies.’ Astronomers have found mysterious, giant loops of ultraviolet light around old, massive galaxies, which were presumed to be “dead,” and these galaxies seem to have come back to life. Somehow these “over-the-hill galaxies” have been infused with fresh gas to form new stars that power these truly gargantuan rings, some of which could encircle several Milky Way galaxies.

The discovery of these rings implies that old bloated galaxies that were once devoid of star-making can be reignited with star birth, and that galaxy evolution does not proceed straight from the cradle to the grave.

“In a galaxy’s lifetime, it must make the transition from an active, star-forming galaxy to a quiescent galaxy that does not form stars,” said Samir Salim, lead author of a recent study and a research scientist in the department of astronomy at Indiana University, Bloomington. “But it is possible this process goes the other way, too, and that old galaxies can be rejuvenated.”

Using two orbiting observatories, NASA’s Galaxy Evolution Explorer and Hubble Space Telescope, the astronomers surveyed a vast region of the sky in ultraviolet light. GALEX picked out 30 elliptical and lens-shaped “early” galaxies with puzzlingly strong ultraviolet emissions but no signs of visible star formation, and Hubble was used to take a closer look.

What Hubble showed shocked the astronomers. Three-quarters of the galaxies were spanned by great, shining rings of ultraviolet light, with some ripples stretching 250,000 light-years. A few galaxies even had spiral-shaped ultraviolet features.

“We haven’t seen anything quite like these rings before,” said Michael Rich, co-author of the paper and a research astronomer at UCLA. “These beautiful and very unusual objects might be telling us something very important about the evolution of galaxies.”

But astronomers are unsure where the gas for this galactic resurrection came from and how it has created rings. One possibility is that a smaller galaxy merged with a big, old one, bringing in fresh gas to spawn hordes of new stars, and could in rare instances give rise to the ring structures as well.

But the researchers have their doubts about this origin scenario. “To create a density shock wave that forms rings like those we’ve seen, a small galaxy has to hit a larger galaxy pretty much straight in the center,” said Salim. “You have to have a dead-on collision, and that’s very uncommon.”

Another option that the astronomers like better is that the rejuvenating spark could have come from a gradual sopping-up of the gas in the so-called intergalactic medium, the thin soup of material between galaxies. This external gas could generate these rings, especially in the presence of bar-like structures that span some galaxies’ centers.

Ultimately, more observations will be needed to show how these galaxies began growing younger and lit up with humongous halos. Salim and Rich plan to search for more evidence of bars, as well as faint structures that might be the remnants of stellar blooms that occurred in the galaxies’ pasts. Rather like recurring seasons, it may be that galaxies stirred from winter can breed stars again and then bask in another vibrant, ultraviolet-soaked summer.

The study detailing the findings appeared in the April 21 issue of the Astrophysical Journal.

Source: JPL

Posted on by Nancy Atkinson

Breathtaking Galaxy Amid the Dense Coma Cluster

A majestic face-on spiral galaxy located deep within the Coma Cluster of galaxies. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

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The Coma Cluster is a huge, densely populated cluster, with thousands of galaxies closely bunched together. Amid the bedlam of ellipticals, lenticulars and irregulars is this majestic face-on spiral galaxy known as NGC 4911. Hubble stared long and deep to get this highly detailed image of this particular galaxy located deep within the Coma Cluster. Data from three different years and 28 hours of exposure time were combined to capture this breathtaking look at spiral arms, glowing newborn star clusters and iridescent pink clouds of hydrogen, meaning there is ongoing star formation.

The Coma Cluster lies 320 million light-years away in the northern constellation Coma Berenices. As usual for clusters like this, there are only a few young spirals galaxies, and Hubble magnificently captured one of them in all its glory, using long exposure times with the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys.

Source: HubbleSite

Posted on by Nancy Atkinson

Space Telescopes Team Up to Capture Spectacular Galactic Collision

A new image of two tangled galaxies has been released by NASA's Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long antenna-like arms seen in wide-angle views of the system. These features were produced in the collision. Image credit: Chandra: NASA/CXC/SAO, Spitzer: NASA/JPL-Caltech, Hubble: NASA/STScI

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From JPL:

A new image of two tangled galaxies has been released by NASA’s Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long, antenna-like arms seen in wide-angle views of the system. These features were produced in the collision.

The collision, which began more than 100 million years ago and is still occurring, has triggered the formation of millions of stars in clouds of dusts and gas in the galaxies. The most massive of these young stars have already sped through their evolution in a few million years and exploded as supernovas.

The X-ray image from Chandra shows huge clouds of hot, interstellar gas, which have been injected with rich deposits of elements from supernova explosions. This enriched gas, which includes elements such as oxygen, iron, magnesium and silicon, will be incorporated into new generations of stars and planets. The bright, point-like sources in the image are produced by material falling onto black holes and neutron stars that are remnants of the massive stars. Some of these black holes may have masses that are almost one hundred times that of the sun.

The Spitzer data show infrared light from warm dust clouds that have been heated by newborn stars, with the brightest clouds lying in the overlap region between the two galaxies. The Hubble data reveal old stars and star-forming regions in gold and white, while filaments of dust appear in brown. Many of the fainter objects in the optical image are clusters containing thousands of stars.

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

Cosmologists Provide Closest Measure of Elusive Neutrino

Slices through the SDSS 3-dimensional map of the distribution of galaxies. Earth is at the center, and each point represents a galaxy, typically containing about 100 billion stars. Galaxies are colored according to the ages of their stars, with the redder, more strongly clustered points showing galaxies that are made of older stars. The outer circle is at a distance of two billion light years. The region between the wedges was not mapped by the SDSS because dust in our own Galaxy obscures the view of the distant universe in these directions. Both slices contain all galaxies within -1.25 and 1.25 degrees declination. Credit: M. Blanton and the Sloan Digital Sky Survey.

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Cosmologists – and not particle physicists — could be the ones who finally measure the mass of the elusive neutrino particle. A group of cosmologists have made their most accurate measurement yet of the mass of these mysterious so-called “ghost particles.” They didn’t use a giant particle detector but used data from the largest survey ever of galaxies, the Sloan Digital Sky Survey. While previous experiments had shown that neutrinos have a mass, it is thought to be so small that it was very hard to measure. But looking at the Sloan data on galaxies, PhD student Shawn Thomas and his advisers at University College London put the mass of a neutrino at no greater than 0.28 electron volts, which is less than a billionth of the mass of a single hydrogen atom. This is one of the most accurate measurements of the mass of a neutrino to date.

Their work is based on the principle that the huge abundance of neutrinos (there are trillions passing through you right now) has a large cumulative effect on the matter of the cosmos, which naturally forms into “clumps” of groups and clusters of galaxies. As neutrinos are extremely light they move across the universe at great speeds which has the effect of smoothing this natural “clumpiness” of matter. By analysing the distribution of galaxies across the universe (i.e. the extent of this “smoothing-out” of galaxies) scientists are able to work out the upper limits of neutrino mass.

A neutrino is capable of passing through a light year –about six trillion miles — of lead without hitting a single atom.

Central to this new calculation is the existence of the largest ever 3D map of galaxies, called Mega Z, which covers over 700,000 galaxies recorded by the Sloan Digital Sky Survey and allows measurements over vast stretches of the known universe.

“Of all the hypothetical candidates for the mysterious Dark Matter, so far neutrinos provide the only example of dark matter that actually exists in nature,” said Ofer Lahav, Head of UCL’s Astrophysics Group. “It is remarkable that the distribution of galaxies on huge scales can tell us about the mass of the tiny neutrinos.”

The Cosmologists at UCL were able to estimate distances to galaxies using a new method that measures the colour of each of the galaxies. By combining this enormous galaxy map with information from the temperature fluctuations in the after-glow of the Big Bang, called the Cosmic Microwave Background radiation, they were able to put one of the smallest upper limits on the size of the neutrino particle to date.

“Although neutrinos make up less than 1% of all matter they form an important part of the cosmological model,” said Dr. Shaun Thomas. “It’s fascinating that the most elusive and tiny particles can have such an effect on the Universe.”

“This is one of the most effective techniques available for measuring the neutrino masses,” said Dr. Filipe Abadlla. “This puts great hopes to finally obtain a measurement of the mass of the neutrino in years to come.”

The authors are confident that a larger survey of the Universe, such as the one they are working on called the international Dark Energy Survey, will yield an even more accurate weight for the neutrino, potentially at an upper limit of just 0.1 electron volts.
The results are published in the journal Physical Review Letters.

Source: University College London