Posted on by Tammy Plotner

Cooking Up Stars In Cygnus X

A bubbling cauldron of star birth is highlighted in this new image from NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

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Thanks to the incredible infra-red imagery of NASA’s Spitzer Space Telescope, we’re able to take a look into a tortured region of star formation. Infrared light in this image has been color-coded according to wavelength. Light of 3.6 microns is blue, 4.5-micron light is blue-green, 8.0-micron light is green, and 24-micron light is red. The data was taken before the Spitzer mission ran out of its coolant in 2009, and began its “warm” mission. This image reveals one of the most active and tumultuous areas of the Milky Way – Cygnus X. Located some 4,500 light years away, the violent-appearing dust cloud holds thousands of massive stars and even more of moderate size. It is literally “star soup”…

“Spitzer captured the range of activities happening in this violent cloud of stellar birth,” said Joseph Hora of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who presented the results today at the 219th meeting of the American Astronomical Society in Austin, Texas. “We see bubbles carved out by massive stars, pillars of new stars, dark filaments lined with stellar embryos and more.”

According to popular theory, stars are created in regions similar to Cygnus X. As their lives progress, they drift away from each other and it is surmised the Sun once belonged to a stellar association formed in a slightly less extreme environment. In regions like Cygnus X, the dust clouds are characterized with deformations caused by stellar winds and high radiation. The massive stars literally shred the clouds that birth them. This action can stop other stars from forming… and also cause the rise of others.

“One of the questions we want to answer is how such a violent process can lead to both the death and birth of new stars,” said Sean Carey, a team member from NASA’s Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. “We still don’t know exactly how stars form in such disruptive environments.”

Thanks to Spitzer’s infra-red data, scientists are now able to paint a clearer picture of what happens in dusty complexes. It allows astronomers to peer behind the veil where embryonic stars were once hidden – and highlights areas like pillars where forming stars pop out inside their cavities. Another revelation is dark filaments of dust, where embedded stars make their home. It is visions like this that has scientists asking questions… Questions such as how filaments and pillars could be related.

“We have evidence that the massive stars are triggering the birth of new ones in the dark filaments, in addition to the pillars, but we still have more work to do,” said Hora.

Original Story Source: NASA Spitzer News Release.

Posted on by Ray Sanders

A Psychedelic Guide to Tycho’s Supernova Remnant

Gamma-rays detected by Fermi's LAT show that the remnant of Tycho's supernova shines in the highest-energy form of light. This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data. Image Credit: Gamma ray, NASA/DOE/Fermi LAT Collaboration; X-ray, NASA/CXC/SAO; Infrared, NASA/JPL-Caltech; Optical, MPIA, Calar Alto, O. Krause et al. and DSS)

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By no means are we suggesting that NASA’s Fermi Gamma-Ray Space Telescope can induce altered states of awareness, but this ‘far-out’ image is akin to 1960’s era psychedelic art. However, the data depicted here provides a new and enlightened way of looking at an object that’s been observed for over 400 years. After years of study, data collected by Fermi has revealed Tycho’s Supernova Remnant shines brightly in high-energy gamma rays.

The discovery provides researchers with additional information on the origin of cosmic rays (subatomic particles that are on speed). The exact process that gives cosmic rays their energy isn’t well understood since charged particles are easily deflected by interstellar magnetic fields. The deflection by interstellar magnetic fields makes it impossible for researchers to track cosmic rays to their original sources.

“Fortunately, high-energy gamma rays are produced when cosmic rays strike interstellar gas and starlight. These gamma rays come to Fermi straight from their sources,” said Francesco Giordano at the University of Bari in Italy.

But here’s some not-so-psychedelic facts about supernova remnants in general and Tycho’s in particular:

When a massive star reaches the end of its lifetime, it can explode, leaving behind a supernova remnant consisting of an expanding shell of hot gas propelled by the blast shockwave. In many cases, a supernova explosion can be visible on Earth – even in broad daylight. In November of 1572, a new “star” was discovered in the constellation Cassiopeia. The discovery is now known to be the most visible supernova in the past 400 years. Often called “Tycho’s supernova”, the remnant shown above is named after Danish astronomer Tycho Brahe, who spent a great deal of time studying the supernova.

Tycho's map shows the supernova's position (largest symbol, at top) relative to the stars that form Cassiopeia. Image credit: University of Toronto
The 1572 supernova event occurred when the night sky was considered to be a fixed and unchanging part of the universe. Tycho’s account of the discovery gives a sense of just how profound his discovery was. Regarding his discovery, Tycho stated, “When I had satisfied myself that no star of that kind had ever shone forth before, I was led into such perplexity by the unbelievability of the thing that I began to doubt the faith of my own eyes, and so, turning to the servants who were accompanying me, I asked them whether they too could see a certain extremely bright star…. They immediately replied with one voice that they saw it completely and that it was extremely bright”

In 1949, physicist Enrico Fermi (the namesake for the Fermi Gamma-ray Space Telescope) theorized that high-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. Following up on Fermi’s work, astronomers learned that supernova remnants might be the best candidate sites for magnetic fields of such magnitude.

One of the main goals of the Fermi Gamma-ray Space Telescope is to better understand the origins of cosmic rays. Fermi’s Large Area Telescope (LAT) can survey the entire sky every three hours, which allows the instrument to build a deeper view of the gamma-ray sky. Since gamma rays are the most energetic form of light, studying gamma ray concentrations can help researchers detect the particle acceleration responsible for cosmic rays.

Co-author Stefan Funk (Kavli Institute for Particle Astrophysics and Cosmology) adds, “This detection gives us another piece of evidence supporting the notion that supernova remnants can accelerate cosmic rays.”

After scanning the sky for nearly three years, Fermi’s LAT data showed a region of gamma-ray emissions associated with the remnant of Tycho’s supernova. Keith Bechtol, (KIPAC graduate student) commented on the discovery, saying, “We knew that Tycho’s supernova remnant could be an important find for Fermi because this object has been so extensively studied in other parts of the electromagnetic spectrum. We thought it might be one of our best opportunities to identify a spectral signature indicating the presence of cosmic-ray protons”

The team’s model is based on LAT data, gamma-rays mapped by ground-based observatories and X-ray data. The conclusion the team has come to regarding their model is that a process called pion production is the best explanation for the emissions. The animation below depicts a proton moving at nearly the speed of light and striking a slower-moving proton. The protons survive the collision, but their interaction creates an unstable particle — a pion — with only 14 percent of the proton’s mass. In 10 millionths of a billionth of a second, the pion decays into a pair of gamma-ray photons.

If the team’s interpretation of the data is accurate, then within the remnant, protons are being accelerated to near the speed of light. After being accelerated to such tremendous speeds, the protons interact with slower particles and produce gamma rays. With all the amazing processes at work in the remnant of Tycho’s supernova, one could easily imagine how impressed Brahe would be.

And no tripping necessary.

Learn more about the Fermi Gamma-ray Space Telescope at: http://www.nasa.gov/mission_pages/GLAST/main/index.html

Source: Fermi Gamma-ray Space Telescope Mission News

Posted on by Tammy Plotner

In The Dragonfish’s Mouth – The Next Generation Of “SuperStars”

A high-resolution infrared image of Dragonfish association, showing the shell of hot gas. Credit:NASA/JPL-Caltech/GLIMPSE Team/Mubdi Rahman

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At the University of Toronto, a trio of astronomers have been fishing – fishing for a copious catch of young, supermassive stars. What they caught was unprecedented… Hundreds of thousands of stars with several hundreds of these being the most massive kind. They hauled in blue stars dozens of times heavier than the Sun, with light so intense it ate its way through the gas that created it. All that’s left is the hollow egg-shell… A shell that measures a hundred light years across.

Their work will be published in the December 20 issue of the Astrophysical Journal Letters, but the team isn’t stopping there. The next catch is waiting. “By studying these supermassive stars and the shell surrounding them, we hope to learn more about how energy is transmitted in such extreme environments,” says Mubdi Rahman, a PhD candidate in the Department of Astronomy & Astrophysics at the University of Toronto. Rahman led the team, along with supervisors, Professors Dae-Sik Moon and Christopher Matzner.

Is the discovery of a huge factory for massive stars new? No. Astronomers have picked them up in other galaxies, but the distance didn’t allow for a clear picture – even when combined with data from other telescopes. “This time, the massive stars are right here in our galaxy, and we can even count them individually,” Rahman says.

However, studying this bright stellar cache isn’t going to be an easy task. Since they are located some 30,000 light years away, the measurements will be extremely labor intensive due to intervening gas and dust. Their light is absorbed, which makes the most luminous of them seem to be smaller and closer. To make matters worse, the fainter stars don’t show up at all. “All this dust made it difficult for us to figure out what type of stars they are,” Rahman says. “These stars are incredibly bright, yet, they’re very hard to see.”

By employing the New Technology Telescope at the European Southern Observatory in Chile, the researchers gathered as much light as possible from a small collection of stars. From this point, they calculated the amount of light each star emitted across the spectrum to determine how many were massive. At least twelve were of the highest order, with a few measuring out to be around a hundred times more massive than the Sun. Before researching the area with a ground-based telescope, Rahman used the WMAP satellite to study the microwave band. There he encountered the glow of the heated gas shell. Then it was Spitzer time… and the imaging began in infra-red.

Once the photos came back the picture was clear… Rahman noticed the stellar egg-shell had a striking resemblance to Peter Shearer’s illustration “The Dragonfish”. And indeed it does look like a mythical creature! With just a bit of imagination you can see a tooth-filled mouth, eyes and even a fin. The interior of the mouth is where the gas has been expelled by the stellar light and propelled forward to form the shell. Not a sight you’d want to encounter on a dark night… Or maybe you would!

“We were able to see the effect of the stars on their surroundings before seeing the stars directly,” Rahman says. This strange heat signature would almost be like watching a face lit by a fire without being able to see the fueling source. Just as red coals are cooler than blue flame, gas behaves the same way in color – with much of it in the infra-red end of the spectrum and only visible to the correct instrumentation. At the other end of the equation are the giant stars which emit in ultra-violet and remain invisible in this type of image. “But we had to make sure what was at the heart of the shell,” Rahman says.

With the positive identification of several massive stars, the team knew they would expire quickly in astronomical terms. “Still, if you thought the inside of the shell was empty, think again,” explains Rahman. For every few hundred superstars, thousands of ordinary stars like the Sun also exist in this region. When the massive ones go supernova, they’ll release metals and heavy atoms which – in turn – may create solar nebulae around the less dramatic stars. This means they could eventually form solar systems of their own

“There may be newer stars already forming in the eyes of the Dragonfish,” Rahman says. Because some areas of the shell appear brighter, researchers surmise the gases contained there are possibly compressing enough to ignite new stars – with enough to go around for many more. However, when there’s no mass or gravity to hold them captive, it would seem they want to fly the nest. “We’ve found a rebel in the group, a runaway star escaping from the group at high speed,” Rahman says. “We think the group is no longer tied together by gravity: however, how the association will fly apart is something we still don’t understand well.”

Original Story Source: In The Dragonfish’s Mouth: The Next Generation Of Superstars To Stir Up Our Galaxy.

Posted on by Tammy Plotner

Massive Stars Start Life Big… Really BIG!

Artist’s impression illustrating the formation process of massive stars. At the end of the formation process, the surrounding accretion disk disappears, revealing the surface of the young star. At this phase the young massive star is much larger than when it has reached a table equilibrium, i.e., when arriving on the so-called main sequence. Copyright: Lucas Ellerbroek/Lex Kaper University of Amsterdam

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It might be hard to believe, but massive stars are larger in their infant stage than they are when fully formed. Thanks to a team of astronomers at the University of Amsterdam, observations have shown that during the initial stages of creation, super-massive stars are super-sized. This research now confirms the theory that massive stars contract until they reach the age of equilibrium.

In the past, one of the difficulties in proving this theory has been the near impossibility of getting a clear spectrum of a massive star during formation due to obscuring dust and gases. Now, using the powerful spectrograph X-shooter on ESO’s Very Large Telescope in Chile, researchers have been able to obtain data on a young star cataloged as B275 in the “Omega Nebula” (M17). Built by an international team, the X-shooter has a special wavelength coverage: from 300 nm (UV) to 2500 nm (infrared) and is the most powerful tool of its kind. Its “one shot” image has now provided us with the first solid spectral evidence of a star on its way to main sequence. Seven times more massive than the Sun, B275 has shown itself to be three times the size of a normal main-sequence star. These results help to confirm present modeling.

When young, massive stars begin to coalesce, they are shrouded in a rotating gas disk where the mass-accretion process starts. In this state, strong jets are also produced in a very complicated mechanism which isn’t well understood. These actions were reported earlier by the same research group. When accretion is complete, the disk evaporates and the stellar surface then becomes visible. As of now, B275 is displaying these traits and its core temperature has reached the point where hydrogen fusion has commenced. Now the star will continue to contract until the energy production at its center matches the radiation at the surface and equilibrium is achieved. To make the situation even more curious, the X-shooter spectrum has shown B275 to have a measurably lower surface temperature for a star of its type – a very luminous one. This wide margin of difference can be equated to its large radius – and that’s what the results show. The intense spectral lines associated with B275 are consistent with a giant star.

Lead author Bram Ochsendorf, was the man to analyze the spectrum of this curious star as part of his Master’s research program at the University of Amsterdam. He has also began his PhD project in Leiden. Says Ochsendorf, “The large wavelength coverage of X shooter provides the opportunity to determine many stellar properties at once, like the surface temperature, size, and the presence of a disk.”

The spectrum of B275 was obtained during the X-shooter science verification process by co-authors Rolf Chini and Vera Hoffmeister from the Ruhr-Universitaet in Bochum, Germany. “This is a beautiful confirmation of new theoretical models describing the formation process of massive stars, obtained thanks to the extreme sensitivity of X-shooter”, remarks Ochsendorf’s supervisor Prof. Lex Kaper.

Original Story Source: First firm spectral classification of an early-B pre-main-sequence star: B275 in M17.

Posted on by Tammy Plotner

Cygnus X – A Cosmic-ray Cocoon

Cygnus X hosts many young stellar groupings, including the OB2 and OB9 associations and the cluster NGC 6910. The combined outflows and ultraviolet radiation from the region's numerous massive stars have heated and pushed gas away from the clusters, producing cavities of hot, lower-density gas. In this 8-micron infrared image, ridges of denser gas mark the boundaries of the cavities. Bright spots within these ridges show where stars are forming today. Credit: NASA/IPAC/MSX

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Situated about 4,500 light-years away in the constellation of Cygnus is a veritable star factory called Cygnus X… one estimated to have enough “raw materials” to create as many as two million suns. Caught in the womb are stellar clusters and OB associations. Of particular interest is one labeled Cygnus OB2 which is home to 65 of the hottest, largest and meanest O-type stars known – and close to 500 B members. The O boys blast out holes in the dust clouds in intense outflows, disrupting cosmic rays. Now, a study using data from NASA’s Fermi Gamma-ray Space Telescope is showing us this disturbance can be traced back to its source.

Discovered some 60 years ago in radio frequencies, the Cygnus X region has long been of interest, but dust-veiled at optical wavelengths. By employing NASA’s Fermi Gamma-ray Space Telescope, scientists are now able to peer behind the obscuration and take a look at the heart through gamma ray observations. In regions of star formation like Cygnus X, subatomic particles are produced and these cosmic rays shoot across our galaxy at light speed. When they collide with interstellar gas, they scatter – making it impossible to trace them to their point of origin. However, this same collision produces a gamma ray source… one that can be detected and pinpointed.

“The galaxy’s best candidate sites for cosmic-ray acceleration are the rapidly expanding shells of ionized gas and magnetic field associated with supernova explosions.” says the FERMI team. “For stars, mass is destiny, and the most massive ones — known as types O and B — live fast and die young.”

Because these star types aren’t very common, regions like Cygnus X become important star laboratories. Its intense outflows and huge amount of mass fills the prescription for study. Within its hollowed-out walls, stars reside in layers of thin, hot gas enveloped in ribbons of cool, dense gas. It is this specific area in which Fermi’s LAT instrumentation excels – detecting an incredible amount of gamma rays.

“We are seeing young cosmic rays, with energies comparable to those produced by the most powerful particle accelerators on Earth. They have just started their galactic voyage, zig-zagging away from their accelerator and producing gamma rays when striking gas or starlight in the cavities,” said co-author Luigi Tibaldo, a physicist at Padova University and the Italian National Institute of Nuclear Physics.

Clocked at up to 100 billion electron volts by the LAT, these highly accelerated particles are revealing the extreme origin of gamma-ray emission. For example, visible light is only two to three electron volts! But why is Cygnus X so special? It entangles its sources in complex magnetic fields and keeps the majority of them from escaping. All thanks to those high mass stars…

“These shockwaves stir the gas and twist and tangle the magnetic field in a cosmic-scale jacuzzi so the young cosmic rays, freshly ejected from their accelerators, remain trapped in this turmoil until they can leak into quieter interstellar regions, where they can stream more freely,” said co-author Isabelle Grenier, an astrophysicist at Paris Diderot University and the Atomic Energy Commission in Saclay, France.

However, there’s more to the story. The Gamma Cygni supernova remnant is also nearby and may impact the findings as well. At this point, the Fermi team considers it may have created the initial “cocoon” which holds the cosmic rays in place, but they also concede the accelerated particles may have originated through multiple interactions with stellar winds.

“Whether the particles further gain or lose energy inside this cocoon needs to be investigated, but its existence shows that cosmic-ray history is much more eventful than a random walk away from their sources,” Tibaldo added.

Original Story Source: NASA Fermi News.

Posted on by Tammy Plotner

SOFIA Reveals Star-Forming Region W40

This mid-infrared image of the W40 star-forming region of the Milky Way galaxy was captured recently by the FORCAST instrument on the 100-inch telescope aboard the SOFIA flying observatory. (NASA / FORCAST image)

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Around 1957 light years away, a dense molecular cloud resides beside an OB star cluster locked in a massive HII region. The hydrogen envelope is slowly beginning to billow out and separate itself from the molecular gas, but we’re not able to get a clear picture of the situation thanks to interfering dust. However, by engaging NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), we’re now able to take one of the highest resolution mid-infrared looks into the heart of an incredible star-forming region known as W40 so far known to science.

Onboard a modified 747SP airliner, the Faint Object infraRed Camera for the SOFIA Telescope (FORCAST) has been hard at work utilizing its 2.5 meter (100″) reflecting telescope to capture data. The composite image shown above was taken at wavelengths of 5.4, 24.2 and 34.8 microns. Why this range? Thanks to the high flying SOFIA telescope, we’re able to clear Earth’s atmosphere and “get above” the ambient water vapor which blocks the view. Not even the highest based terrestrial telescope can escape it – but FORCAST can!

With about 1/10 the UV flux of the Orion Nebula, region W40 has long been of scientific interest because it is one of the nearest massive star-forming regions known. While some of its OB stars have been well observed at a variety of wavelengths, a great deal of the lower mass stars remain to be explored. But there’s just one problem… the dust hides their information. Thanks to FORCAST, astronomers are able to peer through the obscuration at W40’s center to examine the luminous nebula, scores of neophyte stars and at least six giants which tip the scales at six to twenty times more massive than the Sun.

Why is studying a region like W40 important to science? Because at least half of the Milky Way’s stellar population formed in similar massive clusters, it is possible the Solar System also “developed in such a cluster almost 5 billion years ago”. The stars FORCAST measures aren’t very bright and intervening dust makes them even more dim. But no worries, because this type of study cuts them out of dust that’s only carrying a temperature of a few hundred degrees. All that from a flying observatory!

Now, that’s cool…

Original Story Source: NASA/SOFIA News. For Further Reading: The W40 Cloud Complex and A Chandra Observation of the Obscured Star-Forming Complex W40.

Posted on by Tammy Plotner

The Way Cool Clouds Of The Carina Nebula

The APEX observations, made with its LABOCA camera, are shown here in orange tones, combined with a visible light image from the Curtis Schmidt telescope at the Cerro Tololo Interamerican Observatory. The result is a dramatic, wide-field picture that provides a spectacular view of Carina’s star formation sites. The nebula contains stars equivalent to over 25 000 Suns, and the total mass of gas and dust clouds is that of about 140 000 Suns.

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It’s beautiful…. But it’s cold. By utilizing the submillimetre-wavelength of light, the 12 meter APEX telescope has imaged the frigid, dusty clouds of star formation in the Carina Nebula. Here, some 7500 light-years away, unrestrained stellar creation produces some of the most massive stars known to our galaxy… a picturesque petri dish in which we can monitor the interaction between the neophyte suns and their spawning molecular clouds.

By examining the region in submillimetre light through the eyes of the LABOCA camera on the Atacama Pathfinder Experiment (APEX) telescope on the plateau of Chajnantor in the Chilean Andes, a team of astronomers led by Thomas Preibisch (Universitäts–Sternwarte München, Ludwig-Maximilians-Universität, Germany), in close cooperation with Karl Menten and Frederic Schuller (Max-Planck-Institut für Radioastronomie, Bonn, Germany), have been able to pick apart the faint heat signature of cosmic dust grains. These tiny particles are cold – about minus 250 degrees C – and can only be detected at these extreme, long wavelengths. The APEX LABOCA observations are shown here in orange tones, combined with a visible light image from the Curtis Schmidt telescope at the Cerro Tololo Interamerican Observatory.

This amalgamate image reveals the Carina nebula in all its glory. Here we see stars with mass exceeding 25,000 sun-like stars embedded in dust clouds with six times more mass. The yellow star in the upper left of the image – Eta Carinae – is 100 times the mass of the Sun and the most luminous star known. It is estimated that within the next million years or so, it will go supernova, taking its neighbors with it. But for all the tension in this region, only a small part of the gas in the Carina Nebula is dense enough to trigger more star formation. What’s the cause? The reason may be the massive stars themselves…

With an average life expectancy of just a few million years, high-mass stars have a huge impact on their environment. While initially forming, their intense stellar winds and radiation sculpt the gaseous regions surrounding them and may sufficiently compress the gas enough to trigger star birth. As their time closes, they become unstable – shedding off material until the time of supernova. When this intense release of energy impacts the molecular gas clouds, it will tear them apart at short range, but may trigger star-formation at the periphery – where the shock wave has a lesser impact. The supernovae could also spawn short-lived radioactive atoms which could become incorporated into the collapsing clouds that could eventually produce a planet-forming solar nebula.

Then things will really heat up!

Original Story Source: ESO News Release.

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 Tammy Plotner

Antique Stars Could Help Solve Mysteries Of Early Milky Way

The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO
The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO

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Utilizing ESO’s giant telescopes located in Chile, researchers at the Niels Bohr Institute have been examining “antique” stars. Located at the outer reaches of the Milky Way, these superannuated stellar specimens are unusual in the fact that they contain an over-abundance of gold, platinum and uranium. How they became heavy metal stars has always been a puzzle, but now astronomers are tracing their origins back to our galaxy’s beginning.

It is theorized that soon after the Big Bang event, the Universe was filled with hydrogen, helium and… dark matter. When the trio began compressing upon themselves, the very first stars were born. At the core of these neophyte suns, heavy elements such as carbon, nitrogen and oxygen were then created. A few hundred million years later? Hey! All of the elements are now accounted for. It’s a tidy solution, but there’s just one problem. It would appear the very first stars only had about 1/1000th of the heavy-elements found in sun-like stars of the present.

How does it happen? Each time a massive star reaches the end of its lifetime, it will either create a planetary nebula – where layers of elements gradually peel away from the core – or it will go supernova – and blast the freshly created elements out in a violent explosion. In this scenario, the clouds of material once again coalesce… collapse again and form more new stars. It’s just this pattern which gives birth to stars that become more and more “elementally” concentrated. It’s an accepted conjecture – and that’s what makes discovering heavy metal stars in the early Universe a surprise. And even more surprising…

Right here in the Milky Way.

“In the outer parts of the Milky Way there are old ‘stellar fossils’ from our own galaxy’s childhood. These old stars lie in a halo above and below the galaxy’s flat disc. In a small percentage – approximately one to two percent of these primitive stars, you find abnormal quantities of the heaviest elements relative to iron and other ‘normal’ heavy elements”, explains Terese Hansen, who is an astrophysicist in the research group Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen.

The 17 observed stars are all located in the northern sky and could therefore be observed with the Nordic Optical Telescope, NOT on La Palma. NOT is 2.5 meter telescope that is well suited for just this kind of observations, where continuous precise observations of stellar motions over several years can reveal what stars belong to binary star systems.
But the study of these antique stars just didn’t happen overnight. By employing ESO’s large telescopes based in Chile, the team took several years to come to their conclusions. It was based on the findings of 17 “abnormal” stars which appeared to have elemental concentrations – and then another four years of study using the Nordic Optical Telescope on La Palma. Terese Hansen used her master’s thesis to analyse the observations.

“After slaving away on these very difficult observations for a few years I suddenly realised that three of the stars had clear orbital motions that we could define, while the rest didn’t budge out of place and this was an important clue to explaining what kind of mechanism must have created the elements in the stars”, explains Terese Hansen, who calculated the velocities along with researchers from the Niels Bohr Institute and Michigan State University, USA.

What exactly accounts for these types of concentrations? Hansen explains their are two popular theories. The first places the origin as a close binary star system where one goes supernova, inundating its companion with layers of heavier elements. The second is a massive star also goes supernova, but spews the elements out in dispersing streams, impregnating gas clouds which then formed into the halo stars.

The research group has analysed 17 stellar fossils from the Milky Way’s childhood. The stars are small light stars and they live longer than large massive stars. They do not burn hydrogen longer, but swell up into red giants that will later cool and become white dwarves. The image shows the most famous of the stars CS31082-001, which was the first star that uranium was found in.
“My observations of the motions of the stars showed that the great majority of the 17 heavy-element rich stars are in fact single. Only three (20 percent) belong to binary star systems – this is completely normal, 20 percent of all stars belong to binary star systems. So the theory of the gold-plated neighbouring star cannot be the general explanation. The reason why some of the old stars became abnormally rich in heavy elements must therefore be that exploding supernovae sent jets out into space. In the supernova explosion the heavy elements like gold, platinum and uranium are formed and when the jets hit the surrounding gas clouds, they will be enriched with the elements and form stars that are incredibly rich in heavy elements”, says Terese Hansen, who immediately after her groundbreaking results was offered a PhD grant by one of the leading European research groups in astrophysics at the University of Heidelberg.

May all heavy metal stars go gold!

Original Story Source: Niels Bohr Institute News Release. For Further Reading: The Binary Frequency of r-Process-element-enhanced Metal-poor Stars and Its Implications: Chemical Tagging in the Primitive Halo of the Milky Way.

Posted on by Tammy Plotner

Early Galaxy Chemistry: VLT Observes Gamma-Ray Burst

Artist’s impression of a gamma-ray burst shining through two young galaxies in the early Universe. Credit: ESO

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“Shot through the heart and you’re to blame…” There’s nothing more powerful than a gamma-ray burst. These abrupt, mega-bright events are captured by orbiting telescopes where the information is immediately relayed to the ground for observation in visible light and infra-red. Some events are so powerful that they linger for hours or even days. But just how quick can we spot them? A burst cataloged as GRB 090323 was picked up by the NASA Fermi Gamma-ray Space Telescope, then confirmed by the X-ray detector on NASA’s Swift satellite and with the GROND system at the MPG/ESO 2.2-metre telescope in Chile. Within a day it was being studied by ESO’s Very Large Telescope. It was so intense it penetrated its host galaxy and another… heading out on a 12 billion light year journey just to get here.

“When we studied the light from this gamma-ray burst we didn’t know what we might find. It was a surprise that the cool gas in these two galaxies in the early Universe proved to have such an unexpected chemical make-up,” explains Sandra Savaglio (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the paper describing the new results. “These galaxies have more heavy elements than have ever been seen in a galaxy so early in the evolution of the Universe. We didn’t expect the Universe to be so mature, so chemically evolved, so early on.”

As the brilliant beacon passed through the galaxies, the gases performed as a filter, absorbing some wavelengths of light. But the real kicker here is we wouldn’t have even known these galaxies existed if it weren’t for the gamma-ray burst! Because the light was affected, astronomers were able to detect the “composition of the cool gas in these very distant galaxies, and in particular how rich they were in heavy elements.” It had been surmised that early galaxies would have less heavy elements since their stellar populations weren’t old enough to have produced them… But the findings pointed otherwise. These new galaxies were rich in heavy elements and going against what we thought we knew about galactic evolution.

So exactly what does that mean? It would appear these new, young galaxies are forming stars at an incredible rate. To enrich their gases so quickly, it’s possible they are in a merger process. While this isn’t a new concept, it just may support the theory that gamma-ray bursts can be associated with “vigorous massive star formation”. Furthermore, it’s surmised that rapid stellar growth may have simply stopped in the primordial Universe. What’s left that we can observe some 12 billion years later are mere shadows of what once was… like cool dwarf stars and black holes. These two newly discovered galaxies are like finding a hidden stain on the outskirts of the distant Cosmos.

“We were very lucky to observe GRB 090323 when it was still sufficiently bright, so that it was possible to obtain spectacularly detailed observations with the VLT. Gamma-ray bursts only stay bright for a very short time and getting good quality data is very hard. We hope to observe these galaxies again in the future when we have much more sensitive instruments, they would make perfect targets for the E-ELT,” concludes Savaglio.

Original Story Source: ESO Press Release. For Further Reading: Super-solar Metal Abundances in Two Galaxies at z ~ 3.57 revealed by the GRB 090323 Afterglow Spectrum.