Astronomers have glimpsed into the birth of a star, and have seen what could be the youngest known star at the very moment it is being born. “It’s very difficult to detect objects in this phase of star formation, because they are very short-lived and they emit very little light,” said Xuepeng Chen, from Yale University and lead author of a new paper. Not yet fully developed into a true star, the object is in the earliest stages of star formation and has just begun pulling in matter from a surrounding envelope of gas and dust. The team detected the faint light emitted by the nearby dust.
Using the Submillimeter Array in Hawaii and the Spitzer Space Telescope, the astronomers studied L1448-IRS2E, located in the Perseus star-forming region, about 800 light years away within our Milky Way galaxy.
Stars form out of large, cold, dense regions of gas and dust called molecular clouds, which exist throughout the galaxy. Astronomers think L1448-IRS2E is in between the prestellar phase, when a particularly dense region of a molecular cloud first begins to clump together, and the protostar phase, when gravity has pulled enough material together to form a dense, hot core out of the surrounding envelope.
Most protostars are between one to 10 times as luminous as the Sun, with large dust envelopes that glow at infrared wavelengths. Because L1448-IRS2E is less than one tenth as luminous as the Sun, the team believes the object is too dim to be considered a true protostar. Yet they also discovered that the object is ejecting streams of high-velocity gas from its center, confirming that some sort of preliminary mass has already formed and the object has developed beyond the prestellar phase. This kind of outflow is seen in protostars (as a result of the magnetic field surrounding the forming star), but has not been seen at such an early stage until now.
The team hopes to use the new Herchel space telescope, launched last May, to look for more of these objects caught between the earliest stages of star formation so they can better understand how stars grow and evolve. “Stars are defined by their mass, but we still don’t know at what stage of the formation process a star acquires most of its mass,” said Héctor Arce, also from Yale. “This is one of the big questions driving our work.”
Other authors of the paper include Qizhou Zhang and Tyler Bourke of the Harvard-Smithsonian Center for Astrophysics; and Ralf Launhardt, Markus Schmalzl and Thomas Henning of the Max Planck Institute for Astronomy.
The new study appears in the current issue of the Astrophysical Journal.
No, not really (but I got all three key words into the title in a way that sorta makes sense).
Astronomers, like most scientists, just love acronyms; unfortunately, like most acronyms, on their own the ones astronomers use make no sense to non-astronomers.
And sometimes not even when written in full:
GOODS = Great Observatories Origins Deep Survey; OK that’s vaguely comprehensible (but what ‘origins’ is it about?)
AEGIS = All-wavelength Extended Groth strip International Survey; hmm, what’s a ‘Groth’?
GEMS = Galaxy Evolution from Morphology and SEDs; is Morphology the study of Morpheus’ behavior? And did you guess that the ‘S’ stood for ‘SEDs’ (not ‘Survey’)?
But, given that these all involve a ginormous amount of the ‘telescope time’ of the world’s truly great observatories, to produce such visually stunning images as the one below (NOT!), why do astronomers do it? GEMS tile#58 (MPIfA)
Astronomy has made tremendous progress in the last century, when it comes to understanding the nature of the universe in which we live.
As late as the 1920s there was still debate about the (mostly faint) fuzzy patches that seemed to be everywhere in the sky; were the spiral-shaped ones separate ‘island universes’, or just funny blobs of gas and dust like the Orion nebula (‘galaxy’ hadn’t been invented then)?
Today we have a powerful, coherent account of everything we see in the night sky, no matter whether we use x-ray eyes, night vision (infrared), or radio telescopes, an account that incorporates the two fundamental theories of modern physics, general relativity and quantum theory. We say that all the stars, emission and absorption nebulae, planets, galaxies, supermassive black holes (SMBHs), gas and plasma clouds, etc formed, directly or indirectly, from a nearly uniform, tenuous sea of hydrogen and helium gas about 13.4 billion years ago (well, maybe the SMBHs didn’t). This is the ‘concordance LCDM cosmological model’, known popularly as ‘the Big Bang Theory’.
But how? How did the first stars form? How did they come together to form galaxies? Why did some galaxies’ nuclei ‘light up’ to form quasars (and others didn’t)? How did the galaxies come to have the shapes we see? … and a thousand other questions, questions which astronomers hope to answer, with projects like GOODS, AEGIS, and GEMS.
The basic idea is simple: pick a random, representative patch of sky and stare at it, for a very, very long time. And do so with every kind of eye you have (but most especially the very sharp ones).
By staring across as much of the electromagnetic spectrum as possible, you can make a chart (or graph) of the amount of energy is coming to us from each part of that spectrum, for each of the separate objects you see; this is called the spectral energy distribution, or SED for short.
By breaking the light of each object into its rainbow of colors – taking a spectrum, using a spectrograph – you can find the tell-tale lines of various elements (and from this work out a great deal about the physical conditions of the material which emitted, or absorbed, the light); “light” here is shorthand for electromagnetic radiation, though mostly ultraviolet, visible light (which astronomers call ‘optical’), and infrared (near, mid, and far).
By taking really, really sharp images of the objects you can classify, categorize, and count them by their shape, morphology in astronomer-speak.
And because the Hubble relationship gives you an object’s distance once you know its redshift, and as distance = time, sorting everything by redshift gives you a picture of how things have changed over time, ‘evolution’ as astronomers say (not to be confused with the evolution Darwin made famous, which is a very different thing).
GOODS
The great observatories are Chandra, XMM-Newton, Hubble, Spitzer, and Herschel (space-based), ESO-VLT (European Southern Observatory Very Large Telescope), Keck, Gemini, Subaru, APEX (Atacama Pathfinder Experiment), JCMT (James Clerk Maxwell Telescope), and the VLA. Some of the observing commitments are impressive, for example over 2 million seconds using the ISAAC instrument (doubly impressive considering that ground-based facilities, unlike space-based ones, can only observe the sky at night, and only when there is no Moon).
There are two GOODS fields, called GOODS-North and GOODS-South. Each is a mere 150 square arcminutes in size, which is tiny, tiny, tiny (you need five fields this size to completely cover the Moon)! Of course, some of the observations extend beyond the two core 150 square arcminutes fields, but every observatory covered every square arcsecond of either field (or, for space-based observatories, both). GOODS-N ACS fields (GOODS/STScI)
GOODS-N is centered on the Hubble Deep Field (North is understood; this is the first HDF), at 12h 36m 49.4000s +62d 12′ 58.000″ J2000. GOODS-S ACS fields (GOODS/STScI)
GOODS-S is centered on the Chandra Deep Field-South (CDFS), at 3h 32m 28.0s -27d 48′ 30″ J2000.
The Hubble observations were taken using the ACS (Advanced Camera for Surveys), in four wavebands (bandpasses, filters), which are approximately the astronomers’ B, V, i, and z. Extended Groth Strip fields (AEGIS) AEGIS
The ‘Groth’ refers to Edward J. Groth who is currently at the Physics Department of Princeton University. In 1995 he presented a ‘poster paper’ at the 185th meeting of the American Astronomical Society entitled “A Survey with the HST“. The Groth strip is the 28 pointings of the Hubble’s WFPC2 camera in 1994, centered on 14h 17m +52d 30′. The Extended Groth Strip (EGS) is considerably bigger than the GOODS fields, combined. The observatories which have covered the EGS include Chandra, GALEX, the Hubble (both NICMOS and ACS, in addition to WFPC2), CFHT, MMT, Subaru, Palomar, Spitzer, JCMT, and the VLA. The total area covered is 0.5 to 1 square degree, though the Hubble observations cover only ~0.2 square degrees (and only 0.0128 for the NICMOS ones). Only two filters were used for the ACS observations (approximately V and I).
I guess you, dear reader, can work out why this is called an ‘All wavelength’ and ‘International Survey’, can’t you? GEMS' ACS fields (MPIfA) GEMS
GEMS is centered on the CDFS (Chandra Deep Field-South, remember?), but covers a much bigger area than GOODS-S, 900 square arcminutes (the largest contiguous field so far imaged by the Hubble at the time, circa 2004; the COSMOS field is certainly larger, but most of it is monochromatic – I band only – so the GEMS field is the largest contiguous color one, to date). It is a mosaic of 81 ACS pointings, using two filters (approximately V and z).
Sources: GOODS (STScI), GOODS (ESO), AEGIS, GEMS, ADS
Special thanks to reader nedwright for catching the error re GEMS (and thanks to to readers who have emailed me with your comments and suggestions; much appreciated)
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The Spitzer Space Telescope has found what appear to be two of the earliest and most primitive supermassive black holes known. “We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution,” said Linhua Jiang of the University of Arizona, Tucson, lead author of a paper published this week in Nature.
A quasar is a compact region in the center of a massive galaxy surrounding the central supermassive black hole.
As shown by the image we posted earlier today from the Planck mission, our galaxy – and the Universe – is littered with dust. But scientists believe the very early universe didn’t have any dust — which tells them that the most primitive quasars should also be dust-free. But nobody had seen any “clean” quasars — until now.
Spitzer has identified two — the smallest on record — about 13 billion light-years away from Earth. The quasars, called J0005-0006 and J0303-0019, were first unveiled in visible light using data from the Sloan Digital Sky Survey. That discovery team, which included Jiang, was led by Xiaohui Fan, a coauthor of the recent paper. NASA’s Chandra X-ray Observatory had also observed X-rays from one of the objects. X-rays, ultraviolet and optical light stream out from quasars as the gas surrounding them is swallowed.
“Quasars emit an enormous amount of light, making them detectable literally at the edge of the observable universe,” said Fan. These two data plots from NASA's Spitzer Space Telescope show a primitive supermassive black hole (top) compared to a typical one. Image credit: NASA/JPL-Caltech
When Jiang and his colleagues set out to observe J0005-0006 and J0303-0019 with Spitzer between 2006 and 2009, their targets didn’t stand out much from the usual quasar bunch. Spitzer measured infrared light from the objects along with 19 others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a supermassive black hole weighing more than 100 million suns.
Of the 21 quasars, J0005-0006 and J0303-0019 lacked characteristic signatures of hot dust, the Spitzer data showed. Spitzer’s infrared sight makes the space telescope ideally suited to detect the warm glow of dust that has been heated by feeding black holes.
“We think these early black holes are forming around the time when the dust was first forming in the universe, less than one billion years after the Big Bang,” said Fan. “The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars.”
The astronomers also observed that the amount of hot dust in a quasar goes up with the mass of its black hole. As a black hole grows, dust has more time to materialize around it. The black holes at the cores of J0005-0006 and J0303-0019 have the smallest measured masses known in the early universe, indicating they are particularly young, and at a stage when dust has not yet formed around them.
The Spitzer observations were made before the telescope ran out of its liquid coolant in May 2009, beginning its “warm” mission.
Luminous Blue Variables (LBVs) are a rare class of extremely massive stars that teeter on the very edge of being stable. The most famous of this class of stars is the well studied Eta Carinae. Like many other LBVs, Eta Carinae is shrouded in a nebula of its own making. The instability of the star causes it to throw off large amounts of mass even during its brief main sequence lifetime. What makes these stars so unstable is an open question which has been difficult to answer do the the paucity of known LBVs. Given that the initial mass function predicts that such massive stars should be rare, this is not surprising, but identifying these stars is often made even more difficult due to the reddening caused by their nebulae.
However, an international team working from Russia and South Africa proposes that the nebula itself may be able to help identify potential candidates of LBVs. To test out their hypothesis, they scanned the Spitzer image archives for nebulae with features similar to those of known LBVs. The feature that distinguished potential LBV nebulae from other nebulae was emission only in the 24 ?m images (likely due to the fact that nebulae do not operate as model blackbodies at such wavelengths, but instead emit most strongly at specific wavelengths due to fluorescence).
In their review of potential nebulae, they identified a one known as MN112. To further explore the possibility, the team took high resolution spectra of the central star. They determined the central star had strong similarities to the known LBV P Cygni. Most notably, the candidate LBV showed very strong emission lines for hydrogen and He I right next to absorption lines for the same elements. This is caused by high pressure regions, either in the atmosphere of the star, or as the faster wind from the star interacts with a slower moving nebula around it. The high pressure region becomes more dense and gives emission lines. Since it moves outwards, it is slightly blueshifted and thus, does not appear directly on top of the absorption line caused by the relatively less dense atmosphere. This time of feature is known as a P Cygni profile.
Another identifying feature of Luminous Blue Variables is that they are variable (Surprise!) up to as much as 1-2 magnitudes. The team had records of the star from photographic plates dating back as far as 1965 as well as more recent CCD measurements and found that the star had not been seen to vary significantly from an apparent blue magnitude (mB) of 17. However, in the infrared region, they determined (using their own photometric observations) that the star had brightened by 0.4 magnitudes over the past 19 years. Although this falls short of the expected variability for a LBV, they suggest “it is quite possible that a significant fraction of LBVs (if not all of them) goes through the long quiescent periods (lasting centuries or more; e.g. Lamers 1986) so that the fast variability (on time
scales from years to decades) observed in the vast majority of classical LBVs could be merely due to the selection effect.”
The authors state their intention to continue observation of this candidate LBV “in the hope that the ”duck” will ”quack” in the foreseeable future.”
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Astronomy is all about getting the big picture of our place in the cosmos, but some pictures are bigger than others. This one is really big. The world’s largest image of our Milky Way galaxy went on display today at the Adler Planetarium in Chicago. The image spans an area of 37 meters (120 feet) long by 1 meter (3 feet) wide at its sides, bulging to 2 meters (6 feet) to show the center of our humongous galaxy. The panorama represents 800,000 separate images taken by the Spitzer Space Telescope over a five-year period.
“This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way,” said Sean Carey of NASA’s Spitzer Science Center, speaking when the image was unveiled in 2008 at the American Astronomical Society meeting in St. Louis (see our article and image of the unveiling). “Where previous surveys saw a single source of light, we now see a cluster of stars. With this data, we can learn how massive stars form, map galactic spiral arms and make a better estimate of our galaxy’s star-formation rate.” Spitzer Survey image compiled. Credit: NASA/JPL
Data from Spitzer’s Infrared Array Camera (IRAC) and the Multiband Imaging Photometer were used to create the image.
If you want to download a very large version of this image (2400 x 3000) click here — warning: very big file.
From our vantage point on Earth, we see the Milky Way as a blurry, narrow band of light that stretches across the sky. In the visible, we only see about 5% of what’s actually out there. But with Spitzer’s dust-piercing infrared eyes, astronomers have peered 60,000 light-years away into this fuzzy band, called the galactic plane, and saw all the way to the other side of the galaxy.
The panorama reveals star formation as never seen before on both the large and small scale. Most of the star forming regions had not been seen before this project was undertaken.
I had the good fortune of seeing the image in St. Louis, and I highly recommend taking the opportunity to go see it at the Adler Planetarium if you are in Chicago. Here’s a video that explains how astronomers took the images and put them all together to form this gigantic panorama.
Why – and how — do brown dwarfs form? Since these cosmic misfits fall somewhere between planets and stars in terms of their temperature and mass, astronomers haven’t yet been able to determine how they form: are their beginnings like planets or stars? Now, the Spitzer Space Telescope has found what could be two of the youngest brown dwarfs. While astronomers are still looking to confirm the finding of these so-called “proto brown dwarfs” it has provided a preliminary answer of how these unusual stars form.
The baby brown dwarfs were found in Spitzer data collected in 2005. Astronomers had focused their search in the dark cloud Barnard 213, a region of the Taurus-Auriga complex well known to astronomers as a hunting ground for young objects.
“We decided to go several steps back in the process when (brown dwarfs) are really hidden,” said David Barrado of the Centro de Astrobiología in Madrid, Spain, lead author of the paper, published in the Astronomy & Astrophysics journal. “During this step they would have an (opaque) envelope, a cocoon, and they would be easier to identify due to their strong infrared excesses. We have used this property to identify them. This is where Spitzer plays an important role because Spitzer can have a look inside these clouds. Without it this wouldn’t have been possible.”
Barrado said the findings potentially solve the mystery about whether brown dwarfs form more like stars or planets. The team’s findings? Brown dwarfs form like low-mass stars.
Brown dwarfs are cooler and more lightweight than stars and more massive (and normally warmer) than planets. They are born of the same dense, dusty clouds that spawn stars and planets. But while they may share the same galactic nursery, brown dwarfs are often called “failed” stars because they lack the mass of their hotter, brighter stellar siblings. Without that mass, the gas at their core does not get hot enough to trigger the nuclear fusion that burns hydrogen — the main component of these molecular clouds — into helium. Unable to ignite as stars, brown dwarfs end up as cooler, less luminous objects that are more difficult to detect — a challenge that was overcome in this case by Spitzer’s heat-sensitive infrared vision. This artist's rendering gives us a glimpse into a cosmic nursery as a star is born from the dark, swirling dust and gas of this cloud. Image credit: NASA/JPL-Caltech
Young brown dwarfs also evolve rapidly, making it difficult to catch them when they are first born. The first brown dwarf was discovered in 1995 and, while hundreds have been found since, astronomers had not been able to unambiguously find them in their earliest stages of formation until now.
Spitzer’s longer-wavelength infrared camera penetrated the dusty natal cloud to observe STB213 J041757. The data, confirmed with near-infrared imaging from Calar Alto Observatory in Spain, revealed not one but two of what would potentially prove to be the faintest and coolest brown dwarfs ever observed.
The twins were observed from around the globe, and their properties were measured and analyzed using a host of powerful astronomical tools. One of the astronomers’ stops was the Caltech Submillimeter Observatory in Hawaii, which captured the presence of the envelope around the young objects. That information, coupled with what they had from Spitzer, enabled the astronomers to build a spectral energy distribution — a diagram that shows the amount of energy that is emitted by the objects in each wavelength.
From Hawaii, the astronomers made additional stops at observatories in Spain (Calar Alto Observatory), Chile (Very Large Telescopes) and New Mexico (Very Large Array). They also pulled decade-old data from the Canadian Astronomy Data Centre archives that allowed them to comparatively measure how the two objects were moving in the sky. After more than a year of observations, they drew their conclusions.
“We were able to estimate that these two objects are the faintest and coolest discovered so far,” Barrado said. This theory is bolstered because the change in brightness of the objects at various wavelengths matches that of other very young, low-mass stars.
While further study will confirm whether these two celestial objects are in fact proto brown dwarfs, they are the best candidates so far, Barrado said. He said the journey to their discovery, while difficult, was fun. “It is a story that has been unfolding piece by piece. Sometimes nature takes its time to give up its secrets.”
Lead image caption: This image shows two young brown dwarfs, objects that fall somewhere between planets and stars in terms of their temperature and mass. Image credit: NASA/JPL-Caltech/Calar Alto Obsv./Caltech Sub. Obsv.
All we can say is, “Wow!” In celebration of the International Year of Astronomy 2009, NASA’s Great Observatories — the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory — have collaborated to produce an unprecedented image of the central region of our Milky Way galaxy. This is a never-before-seen view of the turbulent heart of our home galaxy. The image is being unveiled by NASA to commemorate the anniversary of when Galileo first turned his telescope to the heavens in 1609. NASA provided this image and the individual images taken by each of the Great Observatories to more than 150 planetariums, museums, nature centers, libraries, and schools across the country.
In this spectacular image, observations using infrared light and X-ray light see through the obscuring dust and reveal the intense activity near the galactic core. Note that the center of the galaxy is located within the bright white region to the right of and just below the middle of the image. The entire image width covers about one-half a degree, about the same angular width as the full moon.
NASA’s Spitzer Space Telescope captured this infrared image of a giant halo of very fine dust around the young star HR 8799. Image credit: NASA/JPL-Caltech/Univ. of Ariz.
Just what is going on over at the star HR 8799? The place is a mess! But we can just blame it on the kids. Young, hyperactive planets circling the star are thought to be disturbing smaller comet-like bodies, causing them to collide and kick up a huge halo of dust. HR 8799 was in the news in November 2008, for being one of the first with imaged planets. Now, NASA’s Spitzer Space Telescope has taken a closer look at this planetary system and found it to be a very active, chaotic and dusty system. Ah, youth: our solar system was likely in a similar mess before our planets found their way to the stable orbits they circle in today.
The Spitzer team, led by Kate Su of the University of Arizona, Tucson, says the giant cloud of fine dust around the disk is very unusual. They say this dust must be coming from collisions among small bodies similar to the comets or icy bodies that make up today’s Kuiper Belt objects in our solar system. The gravity of the three large planets is throwing the smaller bodies off course, causing them to migrate around and collide with each other. Astronomers think the three planets might have yet to reach their final stable orbits, so more violence could be in store. The planets around HR 8799 are about 10 times the mass of Jupiter.
“The system is very chaotic and collisions are spraying up a huge cloud of fine dust,” said Su. “What’s exciting is that we have a direct link between a planetary disk and imaged planets. We’ve been studying disks for a long time, but this star and Fomalhaut are the only two examples of systems where we can study the relationships between the locations of planets and the disks.”
When our solar system was young, it went through similar planet migrations. Jupiter and Saturn moved around quite a bit, throwing comets around, sometimes into Earth. Some say the most extreme part of this phase, called the late heavy bombardment, explains how our planet got water. Wet, snowball-like comets are thought to have crashed into Earth, delivering life’s favorite liquid.
The Spitzer results were published in the Nov. 1 issue of Astrophysical Journal. The observations were made before Spitzer began its “warm” mission and used up its liquid coolant.
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Something strange is going on around a young star called LRLL 31. Astronomers have witnessed a swirling disk of gas and dust which is changing rather quickly; sometimes weekly. This is likely a planet forming disk, however, planets take millions of years to form, so it’s rare to see anything change on time scales we humans can perceive. Another object appears to be pushing a clump of planet-forming material around the star, and this region is offering astronomers with the Spitzer Space Telescope a rare look into the early stages of planet formation.
Astronomer are seeing the light from this disk varying quite frequently. One possible explanation is that a close companion to the star — either a star or a developing planet — could be shoving planet-forming material together, causing its thickness to vary as it spins around the star.
“We don’t know if planets have formed, or will form, but we are gaining a better understanding of the properties and dynamics of the fine dust that could either become, or indirectly shape, a planet,” said James Muzerolle of the Space Telescope Science Institute, Baltimore, Md. Muzerolle is first author of a paper accepted for publication in the Astrophysical Journal Letters. “This is a unique, real-time glimpse into the lengthy process of building planets.”
One theory of planet formation suggests that planets start out as dusty grains swirling around a star in a disk. They slowly bulk up in size, collecting more and more mass like sticky snow. As the planets get bigger and bigger, they carve out gaps in the dust, until a so-called transitional disk takes shape with a large doughnut-like hole at its center. Over time, this disk fades and a new type of disk emerges, made up of debris from collisions between planets, asteroids and comets. Ultimately, a more settled, mature solar system like our own forms.
Before Spitzer was launched in 2003, only a few transitional disks with gaps or holes were known. With Spitzer’s improved infrared vision, dozens have now been found. The space telescope sensed the warm glow of the disks and indirectly mapped out their structures.
Muzerolle and his team set out to study a family of young stars, many with known transitional disks. The stars are about two to three million years old and about 1,000 light-years away, in the IC 348 star-forming region of the constellation Perseus. A few of the stars showed surprising hints of variations. The astronomers followed up on one, LRLL 31, studying the star over five months with all three of Spitzer’s instruments.
The observations showed that light from the inner region of the star’s disk changes every few weeks, and, in one instance, in only one week. “Transition disks are rare enough, so to see one with this type of variability is really exciting,” said co-author Kevin Flaherty of the University of Arizona, Tucson.
Both the intensity and the wavelength of infrared light varied over time. For instance, when the amount of light seen at shorter wavelengths went up, the brightness at longer wavelengths went down, and vice versa.
Muzerolle and his team say that a companion to the star, circling in a gap in the system’s disk, could explain the data. “A companion in the gap of an almost edge-on disk would periodically change the height of the inner disk rim as it circles around the star: a higher rim would emit more light at shorter wavelengths because it is larger and hot, but at the same time, the high rim would shadow the cool material of the outer disk, causing a decrease in the longer-wavelength light. A low rim would do the opposite. This is exactly what we observe in our data,” said Elise Furlan, a co-author from NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
The companion would have to be close in order to move the material around so fast — about one-tenth the distance between Earth and the sun.
The astronomers plan to follow up with ground-based telescopes to see if a companion is tugging on the star hard enough to be perceived. Spitzer will also observe the system again in its “warm” mission to see if the changes are periodic, as would be expected with an orbiting companion. Spitzer ran out of coolant in May of this year, and is now operating at a slightly warmer temperature with two infrared channels still functioning.
“For astronomers, watching anything in real-time is exciting,” said Muzerolle. “It’s like we’re biologists getting to watch cells grow in a petri dish, only our specimen is light-years away.”
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Combining data from the Chandra X-Ray Observatory and the Spitizer Space Telescope allowed astronomers to create this gorgeous new image of Cepheus B. Besides being incredible eye candy, the new image also provides fresh insight into how some stars are born. The research shows that radiation from massive stars may trigger the formation of many more stars than previously thought.
While astronomers have long understood that stars and planets form from the collapse of a cloud of gas, the question of the main causes of this process has remained open.
“Astronomers have generally believed that it’s somewhat rare for stars and planets to be triggered into formation by radiation from massive stars,” said Konstantin Getman of Penn State University, and lead author of the study. “Our new result shows this belief is likely to be wrong.” Chandra image of Cepheus B. Credit: NASA/Chandra team
The new study suggests that star formation in the region of study in this image, Cepheus B, is mainly triggered by radiation from one bright, massive star outside the molecular cloud. According to theoretical models, radiation from this star would drive a compression wave into the cloud triggering star formation in the interior, while evaporating the cloud’s outer layers. The Chandra-Spitzer analysis revealed slightly older stars outside the cloud while the youngest stars with the most protoplanetary disks congregate in the cloud interior — exactly what is predicted from the triggered star formation scenario.
“We essentially see a wave of star and planet formation that is rippling through this cloud,” said co-author Eric Feigelson, also of Penn State. “Outside the cloud, the stars probably have newly born planets while inside the cloud the planets are still gestating.”
Cepheus B is a cloud of mainly cool molecular hydrogen located about 2,400 light years from the Earth. There are hundreds of very young stars inside and around the cloud — ranging from a few millions years old outside the cloud to less than a million in the interior — making it an important testing ground for star formation.
Previous observations of Cepheus B had shown a rim of ionized gas around the molecular cloud and facing the massive star. However, the wave of star formation — an additional crucial feature to identifying the source of the star formation — had not previously been seen. “We can even clock how quickly this wave is traveling and it’s going about 2,000 miles per hour,” said Getman.
The star that is the catalyst for the star formation in Cepheus B, is about 20 times as massive as the Sun, or at least five times weightier than any of the other stars in Cepheus B.
The Chandra and Spitzer data also suggest that multiple episodes of star and planet formation have occurred in Cepheus B over millions of years and that most of the material in the cloud has likely already been evaporated or transformed into stars.
“It seems like this nearby cloud has already made most of its stars and its fertility will soon wane,” said Feigelson. “It’s clear that we can learn a lot about stellar nurseries by combining data from these two Great Observatories.”
A paper describing these results was published in the July 10 issue of the Astrophysical Journal.
