The Large Magellanic Cloud is one of the closest galaxies to our own. Astronomers have now used the power of the ESO’s Very Large Telescope to explore NGC 2035, one of its lesser known regions, in great detail. This new image shows clouds of gas and dust where hot new stars are being born and are sculpting their surroundings into odd shapes. But the image also shows the effects of stellar death — filaments created by a supernova explosion (left). Credit: ESO
Some 160,000 light years away towards the constellation of Dorado (the Swordfish), is an amazing area of starbirth and death. Located in our celestial neighbor, the Large Magellanic Cloud, this huge stellar forge sculpts vast clouds of gas and dust into hot, new stars and carves out ribbons and curls of nebulae. However, in this image taken by ESO’s Very Large Telescope, there’s more. Stellar annihilation also awaits and shows itself as bright fibers left over from a supernova event.
For southern hemisphere observers, one of our nearest galactic neighbors, the Large Magellanic Cloud, is a well-known sight and holds many cosmic wonders. While the image highlights just a very small region, try to grasp the sheer size of what you are looking at. The fiery forge you see is several hundred light years across, and the factory in which it is contained spans 14,000 light years. Enormous? Yes. But compared to the Milky Way, it’s ten times smaller.
Even at such a great distance, the human eye can see many bright regions where new stars are actively forming, such as the Tarantula Nebula. This new image, taken by ESO’s Very Large Telescope at the Paranal Observatory in Chile, explores an area cataloged as NGC 2035 (right), sometimes nicknamed the Dragon’s Head Nebula. But, just what are we looking at?
The Dragon’s Head is an HII region, more commonly referred to as an emission nebula. Here, young stars pour forth energetic radiation and illuminate the surrounding clouds. The radiation tears electrons away from the atoms contained within the gas. These atoms then gel again with other atoms and release light. Swirling in the mix is dark dust, which absorbs the light and creates deep shadows and create contrast in the nebula’s structure.
However, as we look deep into this image, there’s even more… a fiery finale. At the left of the photo you’ll see the results of one of the most violent events in the Universe – a supernova explosion. These troubled tendrils are all that’s left of what once was a star and its name is SNR 0536-67.6. Perhaps when it exploded, it was so bright that it was capable of outshining the Magellanic Cloud… fading away over the weeks or months that followed. However, it left a lasting impression!
Gamma-ray pulsars in the Milky Way's plane, found by volunteers using Einstein@Home. The sky map is from Fermi's Large Area Telescope. The brighter the color you see, the more intense the radiation in that spot. The small flags show the nationality of the volunteers whose computers spotted the pulsars. Credit: Knispel/Pletsch/AEI/NASA/DOE/Fermi LAT Collaboration
Imagine that you’re innocently running your computer in pursuit of helping data crunch a huge science project. Then, out of the thousands of machines running the project, yours happens to stumble across a discovery. That’s what happened to several volunteers with Einstein@Home, which seeks pulsars in data from the Fermi Gamma-Ray Space Telescope, among other projects.
“At first I was a bit dumbfounded and thought someone was playing a hoax on me. But after I did some research,” everything checked out. That someone as insignificant as myself could make a difference was amazing,” stated Kentucky resident Thomas M. Jackson, who contributed to the project.
Pulsars, a type of neutron star, are the leftovers of stars that exploded as supernovae. They rotate rapidly, with such precision in their rotation periods that they have sometimes been likened to celestial clocks. Although the discovery is exciting to the eight volunteers because they are the first to find these gamma-ray pulsars as part of a volunteer computing project, the pulsars also have some interesting scientific features.
Artist’s illustration of a neutron star, a tiny remnant that remains after its predecessor star explodes. Here, the 12-mile (20-kilometer) sphere is compared with the size of Hannover, Germany. Credit: NASA’s Goddard Space Flight Center
The four pulsars were discovered in the plane of the Milky Way in an area that radio telescopes had looked at previously, but weren’t able to find themselves. This means that the pulsars are likely only visible in gamma rays, at least from the vantage point of Earth; the objects emit their radiation in a narrow direction with radio, but a wider stripe with gamma rays. (After the discoveries, astronomers used the Max Planck Institute for Radio Astronomy’s 100-meter Effelsberg radio telescope and the Australian Parkes Observatory to peer at those spots in the sky, and still saw no radio signals.)
Two of the pulsars also “hiccup” or exhibit a pulsar glitch, when the rotation sped up and then fell back to the usual rotation period a few weeks later. Astronomers are still learning more about these glitches, but they do know that most of them happen in young pulsars. All four pulsars are likely between 30,000 and 60,000 years old.
Artist’s conception of a gamma-ray pulsar. Gamma rays are shown in purple, and radio radiation in green. Credit: NASA/Fermi/Cruz de Wilde
“The first-time discovery of gamma-ray pulsars by Einstein@Home is a milestone – not only for us but also for our project volunteers. It shows that everyone with a computer can contribute to cutting-edge science and make astronomical discoveries,” stated co-author Bruce Allen, principal investigator of Einstein@Home. “I’m hoping that our enthusiasm will inspire more people to help us with making further discoveries.”
Einstein@Home is run jointly by the Center for Gravitation and Cosmology at the University of Wisconsin–Milwaukee and the Albert Einstein Institute in Hannover, Germany. It is funded by the National Science Foundation and the Max Planck Society. As for the volunteers, their names were mentioned in the scientific literature and they also received certificates of discovery for their work.
A brown dwarf from the thick-disk or halo is shown. Although astronomers observe these objects as they pass near to the solar system, they spend much of their time away from the busiest part of the Galaxy, and the Milky Way's disk can be seen in the background. Credit: John Pinfield
As the name implies, a brown dwarf is small… only about 7% the size of the Sun. As far as stellar senior citizens go, they’re cool. Zipping along through space at speeds of 100 to 200 kilometers per second, they may have formed back when our galaxy was young – perhaps 10 billion years ago. Now a team of astronomers headed by Dr. David Pinfield at the University of Hertfordshire has identified a pair of the oldest brown dwarfs known… a set of orbs which could be the harbinger of a huge amount of new, unseen objects.
Although we sometimes refer to them as stars, brown dwarfs are in a class of their own. Because they didn’t ignite in nuclear fusion, they don’t generate internal heat like an ordinary star. After they are formed, they continue to cool and fade as time passes. This process makes them very difficult to observe and the discovery of two very old brown dwarfs, with temperatures of 250-600 C is cause for astronomical excitement.
Just how did Pinfield’s team pick such tiny objects out of the vastness of space? The discovery was facilitated thanks to a survey made by the Wide-field Infrared Survey Explorer (WISE), a NASA observatory that scanned the mid-infrared sky from orbit in 2010 and 2011. The ancient objects are cataloged as WISE 0013+0634 and WISE 0833+0052, and they are located in the constellations of Pisces and Hydra. Because they are so elusive, they were also confirmed by large ground-based telescopes (Magellan, Gemini, VISTA and UKIRT).
However, identifying the pair wasn’t easy. Seeing through the eyes of infrared reveals a crowded space – one populated with reddened stars, distant background galaxies and pockets of nebulous gas and dust. Picking out such a small character from a stellar cast would be like finding one tiny pearl in the vastness of an ocean. But Pinfield’s researchers employed a new method which utilizes WISE’s capabilities. As it scanned the sky over and over again, it revealed the cool, brown dwarfs – picking up the faint signature that other searches had missed.
These two particular brown dwarfs are different from the other slow movers of their type. By studying their spectra, the astronomers have identified atmospheres almost entirely comprised of hydrogen. This sets them apart from younger stars which have an abundance of heavier elements. Does being lighter make them speedier? According to Pinfield, “Unlike in other walks of life, the galaxy’s oldest members move much faster than its younger population.”
Stars near to Sun are considered the “local volume” and are created with three overlapping populations – the thin disk, the thick disk and the halo. Each of these layers has a certain amount of age associated with it: the oldest being the thickest and its member stars move up and down at a higher rate of speed. The halo contains both disks, along with the initial materials which formed the very first stars. Thin disk objects abound in the local volume and account for about 97% of the local stars, while thick disk and halo objects are a meager 3%. Chances are, brown dwarfs belong to that smaller percentage which explains why these fast-moving thick-disk/halo objects are only now being revealed.
Just how many may await discovery? Scientists surmise there may be as many as 70 billion brown dwarfs in the galaxy’s thin disk, and the thick disk and halo take up significantly larger galactic volumes. Even at a tiny 3%, this means there could be an army of ancient brown dwarfs in the galaxy. “These two brown dwarfs may be the tip of an iceberg and are an intriguing piece of astronomical archaeology,” said Pinfield. “We have only been able to find these objects by searching for the faintest and coolest things possible with WISE. And by finding more of them we will gain insight into the earliest epoch of the history of the galaxy.”
A simulated dwarf galaxy when the universe was 0.5 billion years old. Magenta represents cool gas, green is warm ionized gas, and red is hot gas. Check out the movie. Image credit: Hopkins et al. 2013.
For the first time, astronomers are able to accurately simulate galaxies from shortly after the big bang to today by including a realistic treatment of the effects stars have on their host galaxies.
For the past few decades astronomers have simulated galaxies by mixing the basic physical ingredients — gravity, gas chemistry and the evolution of the universe — into their models.
For years their simulations have shown that gas cools off quickly and falls to the center of the galaxy. Eventually all of the gas forms stars. But observations show only “10 percent of the gas in the universe actually does so,” CalTech astronomer Dr. Philip Hopkins explained. “And in very small or very large galaxies, the number can go down to well below a percent.”
Models of galaxies create far too many stars and as a result end up weighing more than real galaxies in the observable universe. But in theory the solution is simple: the missing physics is a process known as stellar feedback.
For that, astronomers have to look at how stars help shape the evolution of the galaxies in which they reside. And what they have found is that stars affect their environments drastically.
When stars are very young they are extremely hot and blast off a high amount of radiation into space. This radiation heats up and pushes on the nearby interstellar gas. Later on stellar winds – particles streaming from the surface of stars — also push on the gas, further disrupting nearby star formation. Finally, explosions as supernovae can push the gas to nearly sonic speeds.
While astronomers have understood the missing physics for quite a while, they have not been able to successfully incorporate it a priori into their models. Despite their efforts their simulated galaxies have always weighed more than observed galaxies actually weigh.
Understanding the missing physics is a completely different question than being able to incorporate the missing physics directly into their models.
Instead, astronomers made big assumptions based on what galaxies should look like. At some point in their simulations, they had to go in by hand and tune certain parameters. They would get rid of so much gas until the results roughly matched the galaxies we observe.
“Basically, they (astronomers) said ‘we need there to be winds to explain the observations, so we’re going to insert those winds by hand into our models, and adjust the parameters until it looks like what’s observed,’ ” Hopkins told Universe Today.
At the time tuning their models in this way was the best astronomers could do and their models did help improve our understanding of galaxy evolution. But Hopkins and a team of astronomers from across North America have found a way to incorporate the missing physics — stellar feedback — directly into their models.
The research team is creating simulations that draw from stellar feedback explicitly. The FIRE (Feedback in Realistic Environments) project is a multi-year, multi-institution effort.
While it was no easy task, they incorporated the necessary and dare I say messy physics into their models, allowing for unprecedented accuracy. They tracked the affects radiation and stellar winds have on their environments and included a realistic supernovae rate.
“The result is that we see these stars pushing on the gas, and supernovae explosions sweeping up and ‘blowing out’ large amounts of material from galaxies,” Hopkins explained. “When you follow all of this, the story holds together, and indeed we can explain the observed masses of galaxies just from the input of stars.”
A simulated galaxy when the universe was 11.7 billion years old. Blue regions are young star clusters that have blown away their gas. Red regions are obscured by dust. Make sure the check out the movie by clicking on the image above. Image credit: Hopkins et al. 2013.
The results have been rewarding — providing some pretty cool videos of galaxies forming across the observable universe — and surprising.
It has become clear that the different types of stellar feedback don’t work alone. While the energy given off by stellar winds can push away interstellar gas, it cannot launch the gas out of the galaxy entirely. The necessary propulsion occurs, instead, when a supernova explosion happens nearby.
But this isn’t to say that supernova explosions play a larger role than stellar winds. If the authors left out any stellar feedback mechanism (the radiation from hot young stars, stellar winds, or supernova explosions) the results were equally poor — with too many stars and masses much too large.
“We’ve just begun to explore these new surprises, but we hope that these new tools will enable us to study a whole host of open questions in the field.”
The paper has been submitted for publication in the Monthly Notices of the Royal Astronomical Society and is available for download here.
Hopkins discusses the “Cosmological zoom-in simulation using new stellar feedback” at at workshop at the University of California, Santa Cruz earlier this year:
NGC 3572 seen with a 2.2-meter telescope at the European Southern Observatory's La Silla Observatory in Chile. Credit: ESO/G. Beccari
Star winds are pushing the gas around NGC 3572 into “elephant trunks”, as you can see if you look carefully as this picture snapped by a La Silla Observatory telescope at the European Southern Observatory in Chile. It’s a demonstration of the power of the youngster blue-white stars embedded in the cloud, which are generating huge gusts blowing the gas and dust away from them.
It’s common for young stars to form in groups. After a few million years growing together, their respective gravities pushes everything further apart, and the stars then finish their lifetimes on their own. Looking at young star clusters such as this gives astronomers a better sense about how our own Sun began its life.
If we zoomed closer to those elephant trunks, they would look similar to the famous “Pillars of Creation” image captured in 1995 by the Hubble Space Telescope in the Eagle Nebula (M16). NASA also did a follow-up observation using infrared wavelengths in 2005 and 2011, which made the young stars a bit easier to see amid the gas and dust.
One of the Hubble Space Telescope’s most famous images, the “Pillars of Creation” in the Eagle Nebula. Credit: NASA/ESA
As for the picture of NGC 3572, the high-resolution image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope is also revealing new mysteries that will require further investigation, ESO stated.
“A strange feature captured in this image is the tiny ring-like nebula located slightly above the centre of the image,” ESO wrote. “Astronomers still are a little uncertain about the origin of this curious feature. It is probably a dense leftover from the molecular cloud that formed the cluster, perhaps a bubble created around a very bright hot star. But some authors have considered that it may be some kind of oddly shaped planetary nebula — the remnants of a dying star.”
Astronomers were also surprised by seeing stars older than 10 million years old within this image that were still picking up mass, which implies that planetary formation could take longer than previously believed.
Research was led by ESO astronomer Giacomo Beccari.
Stellar birth is visible in this image of HH 46/47 taken with the Spitzer Space Telescope and Atacama Large Millimeter/submillimeter Array (ALMA). Credit: NASA/JPL-Caltech/ALMA
Talk about birth in the fast lane. Fresh observations of HH 46/47 — an area well-known for hosting a baby star — demonstrate material from the star pushing against the surrounding gas at supersonic speeds.
“HH” stands for Herbig-Haro, a type of object created “when jets shot out by newborn stars collide with surrounding material, producing small, bright, nebulous regions,” NASA stated. It’s a little hard to see what’s inside these regions, however, as they’re clouded by debris (specifically, gas and dust).
The Spitzer space telescope (which looks in infrared) and the massive Chilean Atacama Large Millimeter/submillimeter Array (ALMA) are both designed to look through the stuff to see what’s within. Here’s what they’ve spotted:
– ALMA: The telescope is showing that the gas is moving apart faster than ever believed, which could have echoes on how the star cloud is forming generally. “In turn, the extra turbulence could have an impact on whether and how other stars might form in this gaseous, dusty, and thus fertile, ground for star-making,” NASA added.
Another view of HH 46/47 with the Atacama Large Millimeter/submillimeter Array (ALMA). Credit: ESO/ALMA (ESO/NAOJ/NRAO)/H. Arce. Acknowledgements to Bo Reipurth
– Spitzer: Two supersonic blobs are emerging from the star in the middle and pushing against the gas, creating the big bubbles you can see here. The right-aiming blob has a lot more material to push through than the left one, “offering a handy compare-and-contrast setup for how the outflows from a developing star interact with their surroundings,” NASA stated.
“Young stars like our sun need to remove some of the gas collapsing in on them to become stable, and HH 46/47 is an excellent laboratory for studying this outflow process,” stated Alberto Noriega-Crespo, a scientist at the Infrared Processing and Analysis Center at the California Institute of Technology.
“Thanks to Spitzer, the HH 46/47 outflow is considered one of the best examples of a jet being present with an expanding bubble-like structure.”
Two nascent black holes formed by the collapse of an early supergiant star. From a visualization by by Christian Reisswig (Caltech).
It’s one of the puzzles of cosmology and stellar evolution: how did supermassive black holes get so… well, supermassive… in the early Universe, when seemingly not enough time had yet passed for them to accumulate their mass through steady accretion processes alone? It takes a while to eat up a billion solar masses’ worth of matter, even with a healthy appetite and lots within gravitational reach. But yet there they are: monster black holes are common within some of the most distant galaxies, flaunting their precocious growth even as the Universe was just celebrating its one billionth birthday.
Now, recent findings by researchers at Caltech suggest that these ancient SMBs were formed by the death of certain types of primordial giant stars, exotic stellar dinosaurs that grew large and died young. During their violent collapse not just one but two black holes are formed, each gathering its own mass before eventually combining together into a single supermassive monster.
Watch a simulation and find out more about how this happens below:
To investigate the origins of young supermassive black holes, Christian Reisswig, NASA Einstein Postdoctoral Fellow in Astrophysics at Caltech and Christian Ott, assistant professor of theoretical astrophysics, turned to a model involving supermassive stars. These giant, rather exotic stars are hypothesized to have existed for just a brief time in the early Universe.
Unlike ordinary stars, supermassive stars are stabilized against gravity mostly by their own photon radiation. In a very massive star, photon radiation—the outward flux of photons that is generated due to the star’s very high interior temperatures—pushes gas from the star outward in opposition to the gravitational force that pulls the gas back in.
During its life, a supermassive star slowly cools due to energy loss through the emission of photon radiation. As the star cools, it becomes more compact, and its central density slowly increases. This process lasts for a couple of million years until the star has reached sufficient compactness for gravitational instability to set in and for the star to start collapsing gravitationally.
Previous studies predicted that when supermassive stars collapse, they maintain a spherical shape that possibly becomes flattened due to rapid rotation. This shape is called an axisymmetric configuration. Incorporating the fact that very rapidly spinning stars are prone to tiny perturbations, Reisswig and his colleagues predicted that these perturbations could cause the stars to deviate into non-axisymmetric shapes during the collapse. Such initially tiny perturbations would grow rapidly, ultimately causing the gas inside the collapsing star to clump and to form high-density fragments.
“The growth of black holes to supermassive scales in the young universe seems only possible if the ‘seed’ mass of the collapsing object was already sufficiently large.”
– Christian Reisswig, NASA Einstein Postdoctoral Fellow at Caltech
Composite image from Chandra and Hubble showing supermassive black holes in the early Universe.
These fragments would orbit the center of the star and become increasingly dense as they picked up matter during the collapse; they would also increase in temperature. And then, Reisswig says, “an interesting effect kicks in.” At sufficiently high temperatures, there would be enough energy available to match up electrons and their antiparticles, or positrons, into what are known as electron-positron pairs. The creation of electron-positron pairs would cause a loss of pressure, further accelerating the collapse; as a result, the two orbiting fragments would ultimately become so dense that a black hole could form at each clump. The pair of black holes might then spiral around one another before merging to become one large black hole.
“This is a new finding,” Reisswig says. “Nobody has ever predicted that a single collapsing star could produce a pair of black holes that then merge.”
An exploding star in our home galaxy might be visible to Earth in the next 50 years, astronomers say in a new calculation of the odds of a nearby supernova.
This explosion would be too faint to prove a hazard to Earthlings, and in fact it may not even be visible with the naked eye in the starry sky. Its heat signature, however, would be seen in the right kind of camera as long as we could swing a telescope there fast enough.
“For [researchers], this study suggests that they have a solid chance of doing something that’s never been done before: detect a supernova fast enough to witness what happens at the very beginning of a star’s demise,” wrote Ohio State University in a press release about the research, which was led by university astronomer researcher Scott Adams.
Fishing Boats Meet the Milky Way on the Isle of Wight (south of England) on May 16, 2013. Credit and copyright: Chad Powell.
The challenge with observing a supernova in our own galaxy is the presence of cosmic dust that can sometimes obscure supernovae and other phenomena from our view. However, infrared light is not as badly affected by this and may be able to see something through the obscurity.
To jump on the supernova as it is happening, the scientists propose having a network in place to send out neutrino alerts when these particles, which would arrive at Earth first after an explosion, are detected on Earth. The key is to figure out the difference between neutrinos from space and neutrinos from other sources, such as nuclear reactors, the sun or even spurious glitches.
A University of Tokyo group led the building of a model of a new kind of neutrino detector, a model that is now operating underground in Japan. Called EGADS (Evaluating Gadolinium’s Action on Detector Systems), the water in the system would be “spiked” with a bit of gadolinium, which would reportedly assist with neutrino detections from outside of Earth.
The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles.
“When a neutrino from a Milky Way supernova enters the tank, it can collide with the water molecules and release energy, along with some neutrons,” Ohio State added. “Gadolinium has a great affinity for neutrons, and will absorb them and then re-emit energy of its own. The result would be one detection signal followed by another a tiny fraction of a second later—a “heartbeat” signal inside the tank for each detected neutrino.”
But what about a naked-eye supernova? The researchers say the probability of that is just 20% to 50% in the next century, with southern hemisphere residents having a better chance since more of the galaxy is visible there. The last instance of this happening, by the way, was in 1604.
Where is the coldest place in the Universe? Right now, astronomers consider the “Boomerang Nebula” to have the honors. Located about 5,000 light-years away in the constellation Centaurus, this pre-planetary nebula carries a temperature of about one Kelvin – or a brisk, minus 458 degrees Fahrenheit. That makes it even colder than the natural background temperature of space! What makes it more frigid than the elusive afterglow of the Big Bang? Astronomers are employing the powers of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to tell us more about its chilly properties and unusual shape.
The “Boomerang” is different all the way around. It is not yet a planetary nebula. The fueling light source – the central star – just isn’t hot enough yet to emit the massive amounts of ultra-violet radiation which lights up the structure. Right now it is illuminated by starlight shining off its surrounding dust grains. When it was first observed in optical light by our terrestrial telescopes, the nebula appeared to be shifted to one side and that’s how it got its fanciful name. Subsequent observations with the Hubble Space Telescope revealed an hour-glass structure. Now, enter ALMA. With these new observations, we can see the Hubble images only show part of what’s happening and the dual lobes seen in the older data were probably only a “trick of the light” as presented by optical wavelengths.
“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” said Raghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper published in the Astrophysical Journal. “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”
So what is going on out there that makes the Boomerang such a cool customer? It’s the outflow, baby. The central star is expanding at a frenzied pace and it is lowering its own temperature in the process. A prime example of this is an air conditioner. It uses expanding gas to create a colder core and as the breeze blows over it – or in this case, the expanding shell – the environment around it is cooled. Astronomers were able to determine just how cool the gas in the nebula is by noting how it absorbed the constant of the cosmic microwave background radiation: a perfect 2.8 degrees Kelvin (minus 455 degrees Fahrenheit).
Credit: NASA/ESA“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”
However, the single-dish millimeter wavelength telescopes didn’t see things the same as Hubble. Rather than a skinny waist, they found a fuller figure – a “nearly spherical outflow of material”. According to the news release, ALMA’s unprecedented resolution permitted researchers to determine why there was such a difference in overall appearance. The dual-lobe structure was evident when they focused on the distribution of carbon monoxide molecules as seen at millimeter wavelengths, but only toward the inside of the nebula. The outside was a different story, though. ALMA revealed a stretched, cold gas cloud that was relatively rounded. What’s more, the researchers also pinpointed a thick corridor of millimeter-sized dust grains enveloping the progenitor star – the reason the outer cloud took on the appearance of a bowtie in visible light! These dust grains shielded a portion of the star’s light, allowing just a glimpse in optical wavelengths coming from opposite ends of the cloud.
“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”
There’s even more to these new findings. Even though the perimeter of the nebula is beginning to warm up, it’s still just a bit colder than the cosmic microwave background. What could be responsible? Just ask Einstein. He called it the “photoelectric effect”.
A "super star cluster", Westerlund 1, which is about 16,000 light-years from Earth. It can be found in the southern constellation of Ara. The picture was taken from the European Southern Observatory's VLT Survey Telescope. Credit: ESO/VPHAS+ Survey/N. Wright
The faint green glow you see in that picture is not an early harbringer of Hallowe’en spooks. It’s hydrogen gas clouds found recently nearby W26, a future supernova in the star cluster Westerlund 1.
The European Southern Observatory’s VLT Survey Telescope in Chile spotted the hydrogen in the cluster, which has hundreds of huge stars that are only believed to be a few million years old. (Our solar system, by comparison, is about 4.5 billion years old.)
“Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star,” the European Southern Observatory stated.
“W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionizing radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.”
Funny enough, the nebula that surrounds the red supergiant is similar to the one surrounding SN1987A, a star that exploded as a fairly bright supernova in 1987. “Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise,” ESO added.
