Mega-Star Eta Carinae Isn't a Cosmic Loner

For decades, astronomers have wondered if Eta Carinae, a massive binary star that shines 5 million times brighter than the sun, was unique, as nothing like it had been found in the Milky Way galaxy, or beyond.

But scientists now know that Eta Carinae, located about 7,500 light years from Earth, is not alone. A study using archived Hubble and Spitzer space telescope imagery found five Eta Carinae "twins" in nearby galaxies, astronomers said at the American Astronomical Society meeting in Kissimmee, Fla., on Wednesday.

Aside from its girth, Eta Carinae’s most distinctive feature is an expanding envelope of gas and dust, the result of a massive eruption in the 1840s that spewed the equivalent of more than 10 times the mass of the sun into space.

What triggered Eta Carinae’s eruption remains a mystery, but scientists used telltale fingerprints of its distinctive dust cloud to find five more supermassive stars that experienced similar explosions.

“We’re looking for a rare evolutionary phase in very rare stars -- the rarest of the rare objects,” astronomer Rubab Khan, with NASA’s Goddard Space Flight Center in Greenbelt, Md., told reporters.

Eta Carinae’s twins are far way, up to 26 million light years away -- too far for telescopes to pick out individual stars. Instead, Khan and colleagues developed an optical and infrared blueprint to hunt for similar stars.

The technique compares the amount of ultraviolet and visible light, which is dimmed by the dust cloud, with heating in the dust caused by the light being re-absorbed at longer, mid-infrared wavelengths.

Scientists then tried to find matches with the amount of dust observed around Eta Carinae. Two similar stars were found in the galaxy M83, located about 15 million light years away, and one each in NGC 6946, M101, and M51, located between 18 million and 26 million light-years away.

Khan said each Eta Carinae twin is believed to be a supermassive star buried in gas and dust equivalent to five to 10 times the mass of the sun.

“Eta Carinae is not unique ... It happens in nature. However, it’s very, very rare. This is the first time we can quantitatively say just how rare Eta Carinae is,” Khan said.

Read more at Discovery News

ALMA Spies Baby Stars' Planetary Workshops

This artist's impression shows the formation of massive planets in the dust gap of a transitional disk surrounding a young star.

Planetary formation remains one of the biggest puzzles in modern astronomy. Although we know that the vast majority of stars possess systems of planets — from tiny Mercury-sized rocky worlds to massive gas giants that would dwarf Jupiter — mysteries remain as to how material accretes to form small planetoids and how long it takes for these planetary embryos to plump-up into what we would consider to be planets.

Now, with the help of the awesome Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have zoomed-in on a selection of very young stars, revealing never-before-seen detail in the planet-forming regions surrounding them. And what they found were monster planets, several times more massive than Jupiter, hiding inside the dusty planetary workshops.

When a star is born, it will often be accompanied by a protoplanetary disk. As the star settles and disk matures, small dusty particles accrete (clump together), eventually creating gravitationally-dominant protoplanets that rapidly vacuum up more and more material, growing bigger and more massive. Of particular interest to astronomers are transitional disks that have a surprising lack of dust in their centers, in the region between the disk and star.

This may not seem surprising; astronomers have explained away these features as either a consequence of stellar radiation pressure (as the star matures, its radiation blasts any nearby dust away), or massive planets could be lurking in this zone, having cleared their orbits of dust through their gravitational dominance.

We’ve been stuck at this impasse for some time; how can we tell whether this dust gap is caused by radiation pressure or planetary formation?

This ALMA image combines a view of the dust around the young star HD 135344B (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disc. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU).

This is where ALMA comes in. The array of radio antennae are sensitive to emissions from the gas these transitional disks contain and through studies of 4 young stars, astronomers have found that inside these dust gaps, there are also gas gaps, but they are 3 times thinner. Only with ALMA’s precision observations could these gas gaps be pinpointed and they can mean only one thing.

“Previous observations already hinted at the presence of gas inside the dust gaps,” said astronomer Nienke van der Marel, of Leiden Observatory in the Netherlands. “But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc.”

Although we are looking at very alien star systems, it’s studies such as these that will ultimately reveal how the planets in our own solar system formed, likely clearing up many mysteries surrounding our understanding of planetary evolution. And as observatories become more sophisticated answers are likely to come sooner rather than later.

Read more at Discovery News

This Is the Hottest White Dwarf in Our Galaxy

New observations of a white dwarf reveal that it is a scorcher, at roughly 250,000 degrees Celsius (482,000 Fahrenheit) -- about 2.5 times hotter than a typical star remnant that is just beginning to cool. What's more, scientists discovered the dwarf lives just at the edge of the Milky Way, contradicting previous research showing it is from outside the galaxy.

The new observations come courtesy of ultraviolet observations performed by the Hubble Space Telescope, suggesting that the star was once five times more massive than our own Sun. No one is quite sure how this star got so hot, and its chemical composition still needs to be analyzed.

"The strange thing about this white dwarf (and its cooler twin H1504+65) is the surface composition," wrote lead author Klaus Werner of the University of Tübingen in Germany, in an e-mail to Discovery News. "It is carbon and oxygen without hydrogen and helium. Currently, there is no good explanation for this phenomenon. Commonly, white dwarfs have either hydrogen-dominated or helium-dominated atmospheres."

A little bit is known about RX J0439.8-6809 by modelling its history. It appears the star's temperature peaked at more than 400,000 degrees Celsius about 1,000 years ago. It was spotted in X-ray images about 20 years ago because it was so hot, but it originally was believed to be in the Large Magellanic Cloud, a galaxy outside of our own.

"Future X-ray surveys (eRosita) combined with optical surveys might reveal more of this kind of white dwarf with unusual surface composition," Werner added. "The search for trace elements (other metals) might give hints as to the evolutionary history."

From Discovery News

Violent Tiny Star Is a Magnetic Powerhouse

Some stars are just born with extremely magnetic personalities.

Take TVLM 513-46546 for example. It’s a small M-class red dwarf, a star that belongs to the most populous stellar group in the galaxy. But TVLM 513-46546 would find it hard blending in with the crowd.

As observed by the Atacama Large Millimeter/submillimeter Array (ALMA), this little star was found to have an extremely powerful magnetic field, rivaling the most powerful magnetically active regions on our sun. It is so active, argue astronomers, that if our planet was in orbit around this star, satellites would not function.

“If we lived around a star like this one, we wouldn’t have any satellite communications. In fact, it might be extremely difficult for life to evolve at all in such a stormy environment,” said Peter Williams, of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. and lead author of the study published in the Astrophysical Journal.

TVLM 513-46546 is located some 35 light-years from Earth in the constellation Boötes. It is a teeny tiny star is only 10 percent the mass of our sun, so tiny in fact that it is on the cusp of the bridging gap between what constitutes a star and what constitutes a planet. If the star were any smaller, there would be insufficient pressure in its core to ignite fusion, making it a brown dwarf, or a “failed star.” But a brown dwarf TVLM 513-46546 is not, it is a magnetic powerhouse and one of the most violent stellar objects we’ve seen in the Milky Way.

The red dwarf is spinning rapidly, taking only 2 hours to spin a full rotation — by comparison, our sun takes 25 days to complete one rotation — and this rotation rate could be the root as to why TVLM 513-46546′s magnetic field is so strong.

“This star is a very different beast from our sun, magnetically speaking,” said coauthor Edo Berger, also from the CfA.

When studying the object with ALMA, the researchers detected powerful radio signals that betrayed the star’s magnetic personality. They measured a signal at 95 GHz, a high-frequency radiation produced by a process known as synchrotron emission, which is generated by high-energy electrons rapidly accelerated by intense magnetic fields. From this measured frequency, the researchers realized the star had a global magnetic field hundreds of times more powerful than the average magnetic field observed in our sun. Although our sun can muster the strength to occasionally generate synchrotron emissions at these frequencies, only the most powerful solar flares can generate them.

Read more at Discovery News

Strange Stellar Spirals Could Hide Baby Exoplanets

Artist's illustration of a protoplanetary disc and a young star. Can we spot giant planets from the patterns in spirals?

When planets are in the process of being born, they grow from clouds of gas and dust surrounding their young star. However, penetrating this dense region to see planets coming to be, or to understand if planets outside of the dust are influencing them, is a difficult task.

To face this challenge, new research has found that some spiral patterns in the dust could, however, be evidence of huge planets swimming in its midst.

Scientists observed a protoplanetary disc around star MWC 758, using the ground-based Very Large Telescope. They found a spiral pattern that could suggest a planet lurking nearby. It's about 1.7 times the mass of our sun and only 8 million years old, a youngster compared to the sun's 4.5 billion years. The planet is believed to be outside the arms at about five times Neptune's equivalent distance from the sun.

"Our model with a 10 Jupiter mass planet is the best (and I would say the only) model so far to be able to account for all the major aspects of the arms as seen in the observations," wrote lead author Ruobing Dong, a NASA Hubble Fellow at Lawrence Berkeley National Laboratory and the University of California, in an e-mail to Discovery News. "Also, in such a young system, it is quite reasonable to believe there are giant planets currently forming. 10 Jupiter mass planets have been found around other (much older) stars, for example HR 8799."

A protoplanetary disc around MWC 758, a young star, based on observations from the European Southern Observatory's Very Large Telescope. The spiral arms are each about 10 billion miles long, or more than three times the diameter of Neptune's orbit.

The challenge is these features are hard to spot. You need to be able to see extremely fine detail, which can only be achieved by the Hubble Space Telescope and a few 8-meter ground based telescopes, Dong said. Worse, the light from the star can wash out the details in the disc. Adaptive optics on Earth can help account for that, but such a system to reduce the star's glare does not exist on Hubble.

The James Webb Space Telescope, which launches in 2018, should "in principle" be able to block out the light of the star and perhaps be able to better see these features than Hubble. The challenge, however, is it observes at longer wavelengths of light than Hubble and ground-based telescope, which makes the resolution more blurry. "Without carrying out detailed simulations to examine the predicted performance of JWST in this sort of observations, I would just say it might (work), but not sure," he added.

But if we were to see better in these systems, it would complement all the Kepler space telescope observations of older stars that we already have in hand. We would understand more about the older stars' history by looking at the youngsters, Dong said, using the analogy of observing business mogul (and presidential candidate) Donald Trump today versus when he was a child.

This computer model attempts to duplicate the structure seen in MWC 758. The "X" marked in the picture is where a planet supposedly lurks, unseen among all the dust and creating the arms.

"You don’t know what kind of baby he was when he was two years old," Dong said. "Did he cry a lot? Was he friendly to his playmates in day care? What kind of fairy tales did he like? In one sentence, Kepler finds 70-year-old Trumps, while the significance of our research is that we want to find baby Trumps."

The shape of the arms tells us about the mass of the planet, which they estimate is about 10 times the size of Jupiter. A smaller planet would be too weak to make the arms the shape that we see, according to the simulations, while a larger planet should already have been spotted in the disc, dusty as it is. Dong allowed, however, that there is some uncertainty in the calculations and the planet could be a slightly different mass than predicted.

Read more at Discovery News

Gang of Young Stars Found Loitering at Galaxy's Core

A group of young stars has been caught loitering near the center of the Milky Way galaxy, a region previously thought to be dominated by a more mature population. Astronomers say the stars form a disk (previously unknown to scientists) that passes through the outer part of the dusty, peanut-shaped bulge at the galactic center.

The thick forest of dust located at the Milky Way's galactic center is a place where even the bright flame of a burning star can be nearly impossible for astronomers to see. But scientists are coming up with new ways to pull back the veil on this shadowy region, and now, new observations using the VISTA telescope have identified this previously undiscovered group of youngsters. Check out this video on Space.com to see where the stars are located relative to Earth and the sun.

The entire group of young stars has not been seen directly, but its presence is deduced by the detection of a group of very bright, very unusual stars called Cepheids. These act as though they're attached to a cosmic dimmer switch; they go through regular swings in their apparent brightness over days or months.

Cepheids are a type of variable star, meaning (just as the name suggests) they change over time. They go through regular oscillations in size and temperature, which cause each star to appear as if it were pulsing, going from a peak brightness to a peak dimness, and back again.

These pulsation periods are extremely regular, and in 1908 the astronomer Henrietta Swann Leavitt discovered that brighter Cepehids had longer pulsation periods, and dimmer Cepheids had shorter periods. With this insight, scientists were able to figure out the actual luminosity of these stars (whereas normally scientists only know how bright the star looks from Earth). That information then made it possible to use Cepheids to measure cosmic distances, making these stars an invaluable cosmic tool.

A co-author on the new paper, Daniel Majaess of Saint Mary's University in Nova Scotia, Canada, said in an email, "I couldn't help think how amazed Henrietta Leavitt would be to learn about the important and diverse role Cepheids would play in shaping our understanding of the cosmos, all of which is invariably tied to her seminal discovery of the Cepheid period-luminosity relationship. From helping define the extragalactic distance scale and expansion rate of the universe, to now-seminal constraints on the nature of the mysterious region encompassing the galactic center."

In the new study, a group of scientists report finding 655 new candidate Cepheid stars in the Milky Way. The data comes from the Vista Variables in the Vía Láctea Survey (VVV), completed by the European Southern Observatory's VISTA telescope at the Paranal Observatory in Chile between 2010 and 2014. Cepheids are brighter than most nonvariable stars — several thousand times brighter than Earth's sun, for example — which makes these stars easier to spot, said Istvan Dekany of the Pontifical Catholic University of Chile.

"This discovery is a very powerful demonstration of the recent technological advancement in infrared astronomy," Dekany, who is the lead author on the new paper, told Space.com via email. VISTA's "large field of view and superb near-infrared imaging capability allowed us to penetrate through the vast amount of interstellar dust that is blocking our view towards the inner Milky Way, and probe areas that are invisible in the optical light."

Also necessary to finding the new haul of Cepheids was the amount of time that VISTA spent watching the same area of the sky, which allowed scientists to spot the fluctuations in the Cepheids' brightness.

Among the 655 new Cepheids, 35 are so-called classical Cepheids, and all of them are less than 100 million years old. This makes them juveniles compared to a star like Earth's sun, which is 4.57 billion years old, and only about halfway through its lifetime.

"Classical Cepheids are very rare, 'one in a million' objects," Dekany wrote. Stars are typically born in large groups, so the presence of the young, classical Cepheids indicates that there are other sibling stars nearby. In this way, the scientists say they have traced this new, thin disk of young stars that crosses the galactic bulge.

Scientists previously thought of the galactic bulge as a home to mostly old stars, but finding a population of young stars there is not totally surprising, Dekany said.

Read more at Discovery News

Hubble Zooms-in on Veil Nebula's Shocked Tendrils

These beautiful, shimmering tendrils of plasma are all that remain of an ancient massive star that, approximately 8,000 years ago, died and exploded as a supernova. This zoomed-in section of the Veil Nebula has just been released by the Hubble Space Telescope, revealing the intricate beauty that’s left in the wake of one of the most violent events in the universe.

The Veil Nebula is one of the best known supernova remnants in the sky, featuring vast wispy structures of hot plasma some 110 light-years across. The nebula is located around 2,100 light-years away in the constellation Cygnus, the Swan.

Vast as it may be, this new observation features 6 images stitched together as a mosaic, only spanning 2 light-years, providing a very detailed look at the innermost detail of this fascinating object.

The Veil’s brightest components are caused by the ancient supernova’s shock wave that is traveling through interstellar space, blasting into the edge of a cavity, or bubble, etched out into a region of cool interstellar gas. Viewed edge-on, the crumpled structure of the expanding bubble’s leading edge glows in a range of vivid colors, heated by the interaction between the shock waves and cavity gas.

These colors represent the superheated glow of various different gases in the cavity wall — red is the glow of hydrogen; green is sulfur; blue is oxygen. The less defined, more diffuse glow is caused by cooler gases that was heated by the traveling shock wave in the past.

Read more at Discovery News

Extreme Star Formation Mystery Cracked

Scientists have long pondered how extremely bright, ancient galaxies known as submillimeter galaxies (SMGs) managed to pump out stars 1,000 times faster than the Milky Way does today.

Two theories have dominated the debate. The first is that galaxy collisions drove short-lived, but spectacular bursts of star formation. The other idea is that SMGs are long-lived structures that accumulated mass over time.

“Neither scenario has been successful in fully replicating the observed properties of SMGs,” astronomer Romeel Dave, with the University of the Western Cape, Cape Town, South Africa, wrote in an essay in this week’s Nature.

A new study, also published Nature, details a computer simulation that,  for the first time,  matches observed properties of SMGs. The model shows that the galaxies aren’t transient and that they can generate stars at the incredible rate of 500- to 1,000 solar-mass stars PER YEAR for a billion years.

What makes them so productive? The simulation suggests the galaxies, which date back to about 3 billion years after the Big Bang,  tapped reservoirs of gas to form new stars, rather than rely on mergers with other galaxies.

“In a nutshell, the authors find that SMGs plausibly arise from a ‘perfect storm’ of high rates of gravitationally driven gas accretion, the recycling of previously ejected material and contributions to the systems’ submillimetre luminosity from nearby galaxies,” Dave wrote.

From Discovery News

Ghostly Orb is Dying Star's Final Farewell

When a star like our sun runs out of fuel and begins to die, violent stellar winds rip it to shreds, blasting massive quantities of stellar matter into space. The result is a planetary nebula, a vast bubble of expanding gas that represents a star’s final, beautiful, farewell.

As imaged by the ESO’s Very Large Telescope, this particularly exquisite planetary nebula is called ESO 378-1 and very little was known about the object until the powerful telescope located in northern Chile zoomed in.

Also known as the Southern Owl Nebula, this planetary nebula is nearly 4 light-years wide and joins its visual cousin, the Owl Nebula, in the northern constellation of Hydra (The Female Water Snake).

Planetary nebulae are fairly short-lived stellar phenomena. As the star, with a mass less than 8 times that of our sun, starts to die, a huge envelope of gas expands into interstellar space. The core of the star remains in the center of the planetary nebula, powerful ultraviolet light ionizing the gas, causing it to glow.

When the nebula fades away, a white dwarf star will remain behind, glowing and slowly cooling down for billions of years, long after the nebula is gone.

From Discovery News

Stellar Mystery Solved: Exploding Star is a Lithium Factory

Lithium has been detected in stellar material blasting away from an exploding star, possibly revealing the source of the basic element in young stars, thereby solving a mystery that has perplexed astronomers for decades.

The event, known as a nova, occurred in southern skies in December 2013 near the bright star Beta Centauri. A nova is thought to occur in binary star systems where a white dwarf star pulls hydrogen from its binary partner. Once this material reaches a critical mass, the hydrogen undergoes a runaway fusion reaction, causing the white dwarf to erupt.

It has long been known that novae can produce an array of different chemical elements that enrich the interstellar medium with gases that go on to help form later generations of stars. However, though lithium is theorized to also be produced by these explosions, astronomers have not been able to detect any trace of the element in previous novae.

Lithium is one of the few elements that is thought to have been produced by the Big Bang, nearly 14 billion years ago. However, astronomers have observed a greater abundance of lithium in younger stars than older stars, indicating there must be another production mechanism in the modern universe.

So, in the 1970s, astronomers’ attention shifted to novae as being the culprit. Although rare, and much less powerful than their larger supernova cousins, it was thought that over the history of the Milky Way enough novae likely occurred to explain this abundance of lithium. But observations of novae seeking elusive lithium proved fruitless.

Then Nova Centauri 2013 (also known as V1369 Centauri) lit up our skies, an explosion that was easily visible to the naked eye and the brightest nova so far this century.

As reported in a new study published Wednesday in the Astrophysical Journal Letters, Luca Izzo, from Sapienza University of Rome and ICRANet, Pescara, Italy, and his team used the FEROS instrument on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile, and the PUCHEROS spectrograph on the ESO 0.5-meter telescope at the Observatory of the Pontificia Universidad Catolica de Chile near Santiago, to zoom in on V1369 Centauri.

These new data have revealed a “very clear signature” of lithium speeding away from the stellar explosion at a speed of 2 million kilometers (1.2 million miles) per hour, the first time lithium has ever been seen being produced by a nova.

Read more at Discovery News

Plus-Sized Black Hole Busting Out of Skinny Galaxy

A newfound giant black hole nearly as massive as 7 billion suns is dozens of times larger than astronomers expected given its host galaxy's size, researchers say.

This finding may call most current models of galaxy formation into question, scientists added.

Astronomers investigated a supermassive black hole known as CID-947 using the W.M. Keck Observatory in Hawaii, NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton spacecraft.

This black hole, one of the largest ever seen, formed in the early universe about 11.7 billion years ago — 2 billion years after the Big Bang. The very fast motion of gas near the black hole suggests that it has a very high mass — the equivalent of about 7 billion suns.

The discovery was unexpected. "Our survey was designed to observe the average objects, not the exotic ones," study co-author C. Megan Urry, of Yale University, said in a statement. "This project specifically targeted moderate black holes that inhabit typical galaxies today. It was quite a shock to see such a ginormous black hole."

However, it was the mass of the galaxy surrounding this black hole that most surprised the research team.

"The measurements correspond to the mass of a typical galaxy," study lead author Benny Trakhtenbrot, an astrophysicist at the Swiss Federal Institute of Technology in Zurich, said in a statement. "We therefore have a gigantic black hole within a normal-size galaxy."

Most galaxies, including the Milky Way, possess at their hearts a supermassive black hole with a mass ranging from millions to billions of times the mass of the sun. The supermassive black holes seen up to now usually make up only 0.2 to 0.5 percent of the mass of their galaxies —  far less than CID-947 does.

"The black hole has roughly one-tenth of the mass of the host," Trakhtenbrot told Space.com. "The black hole is massive compared with the normal host galaxy." The result was so surprising that the astronomers had outside experts verify their results independently.

Current models of galaxy formation suggest that galaxies and their supermassive black holes evolve in sync, growing at the same rate. However, CID-947 defies this rule, precociously growing much faster than researchers would have predicted.

"The black hole and the galaxy were not growing in parallel, as many models would suggest," Trakhtenbrot said.

In addition, the scientists found that, although the black hole had reached the end of its growth, stars were still forming in its galaxy. Prior research suggested that radiation and flowing gas from around the black hole would stifle the birth of stars.

Read more at Discovery News

Eerie Dark Cloud Blocks Distant Starlight from View

Like a black fog churning through space, this view of a dark molecular cloud seems to extinguish the sparkle of distant stars.

Believed to be the genesis of a possible star system, this dusty cloud — called LDN1774 — may collapse under mutual gravity in the future, eventually sparking the birth of a protostar and eventual system of planets.

This feature was observed in visible light by the Wide Field Imager, an instrument attached to the European Southern Observatory’s 2.2-meter MPG/ESO telescope at La Silla, Chile, but it’s not the only example of such an ominous looking black cosmic cloud.

Located around 500 light-years from Earth, another pitch black molecular cloud called Barnard 68 resides. Extensively studied by ESO telescopes, this cloud can be probed in infrared wavelengths — this form of radiation can pass through the star-forming material, allowing astronomers to see the earliest stages stellar birth.

From Discovery News

Stunning 3-D View of Hubble's Famous 'Pillars of Creation'

For the first time, astronomers have added a new 3-dimensional perspective to the Hubble Space Telescope’s dazzling view of the Eagle Nebula’s famous “Pillars of Creation.”

Using the MUSE instrument on the European Southern Observatory’s Very Large Telescope (VLT) in Chile, the Eagle Nebula was studied in unprecedented detail, bringing a new perspective to the Pillars — large columns of dust and gas cocooning young stars sparking to life.

These young O and B-class stars are pumping out powerful ultraviolet radiation, destroying the remaining wisps of gas and dust, blasting out cavities in the material and carving the tell-tale shape of the Pillars of Creation that were first imaged in detail by the Hubble Space Telescope some 20 years ago.

MUSE has now added some depth to the Pillars, showing that the left pillar is facing us, but located behind NGC 6611 — a star cluster within the Eagle Nebula. The other pillars are located in front of NGC 6611. The tip of the left pillar is bearing the brunt of the powerful radiation from NGC 6611′s young stars, causing it to glow bright in reflected light. The tips of the other three pillars are facing away from us and are therefore darker.

Within the pillars are dense knots of gas, the locations of protostars in the process of being born.

Using observations such as this ESO view into the Eagle Nebula, scientists hope to better understand how O and B-class stars influence the production of subsequent stars within the nebula in which they themselves had been spawned. The intense radiation and powerful stellar winds can compress the remaining gas, correlling it to accumulate and spark new star formation. But they also destroy the star-foming material inside the nebula, hindering further star birth.

Which process dominates can transform the future landscapes of star-forming nebulae like the Pillars of Creation, so understanding their formative years by creating a 3-D look deep inside these clouds should help us better model the mechnics of stellar evolution.

Read more at Discovery News

Star 'Mass Grave' Surrounds Our Galaxy's Black Hole

Astronomers have zoomed into an X-ray emission region immediately surrounding our galaxy’s supermassive black hole, gaining the highest X-ray resolution view to date, and it looks like they’ve stumbled on a mysterious place where stars go to die.

Sagittarius A*, or Sgr A*, is the enigmatic compact radio source surrounding the supermassive black hole in the center of our galaxy. The black hole, which has a mass 4 million times that of our sun, dominates this region with its extreme gravitational well. Many efforts have been carried out in an attempt to understand the population of stars and other stellar phenomena in the immediate vicinity of Sgr A*, but resolving features from such an extreme environment at a distance of 25,000 light-years is not easy.

Through measurements of X-ray spectra from the black hole’s neighborhood, however, astronomers are gradually adding some detail to Sgr A*’s landscape and in new research published in the journal Nature, it seems there’s a strange population of ‘dead’ stars accumulated in the black hole’s shadow.

Using data from NASA’s NuSTAR X-ray space telescope, high-energy physicist Kerstin Perez, of Haverford College, PA, and Columbia University, New York, and her team have been able to better resolve the signatures of various X-ray emissions and it appears that some sources are consistent with a large population of white dwarf stars.

White dwarfs are the stellar remnants of larger stars that have run out of hydrogen fuel and died. Our sun, for example, after exhausting its fuel in about 5 billion years, will puff up into a huge red giant and then rip itself to shreds, expelling huge quantities of solar matter through violent winds. This will cause chaos in the solar system, destroying planets and producing a vast planetary nebula of hot gas. In the center of all the mess will be a white, glowing ball of degenerate matter, a white dwarf.

From previous studies of white dwarfs elsewhere in our galaxy, astronomers have a good idea as to their X-ray emission profiles, so when studying the few parsecs surrounding Sgr A*, Perez’s team were surprised to find an abundance of white dwarf-like emissions. In short, it looks like they stumbled on a puzzling “mass grave” of dead stars.

“The Galactic Center region is dense with X-ray-emitting objects; it contains the supernova remnant Sagittarius (Sgr) A East, the colliding stellar winds surrounding Sgr A*, the hot plasma of the Sgr A East plume, dozens of magnetic X-ray filaments, and thousands of resolved and unresolved point sources that constitute the Galactic ridge X-ray emission,” the researchers write in their Nature Letters paper.

"Almost anything that can emit X-rays is in the galactic center," said Perez in a NASA Jet Propulsion Laboratory news release. "The area is crowded with low-energy X-ray sources, but their emission is very faint when you examine it at the energies that NuSTAR observes, so the new signal stands out."

Within this mess of X-rays are emissions that aren’t associated with other known emission sources, such as dense molecular gas or dust.

“A natural explanation for our emission is provided by the intermediate polar (a type of cataclysmic variable binary star), which has the hardest spectrum of all accreting magnetic white dwarfs.”

There are some other possible explanations — such as an anomalous population of pulsars (rapidly-spinning neutron stars) — but the most likely source appears to be a large number of white dwarfs orbiting within 10 parsecs (33 light-years) of our Milky Way’s supermassive black hole. The X-ray emission originates from these white dwarfs 'feeding' off binary partners' stellar gas.

If they are white dwarf stars, why are they there? The researchers aren’t too sure, but these observations provide a valuable insight to the stellar dynamics in close proximity to a galaxy’s supermassive black hole.

Read more at Discovery News

Stars May Form in Shadow of Galaxy's Black Hole Beast

Despite the harsh environment created by the monster black hole lurking in the center of the Milky Way galaxy, new observations show that stars — and, potentially, planets — are forming just two light-years away from the colossal giant.

Bright and massive stars were spotted circling the 4-million-solar-mass behemoth more than a decade ago, sparking a debate within the astronomy community. Did they migrate inward after they formed? Or did they somehow manage to form in their original positions?

Most astronomers had said the latter idea seemed far-fetched, given that the black hole wreaks havoc on its surroundings, often stretching any nearby gas into taffylike streamers before it has a chance to collapse into stars. But the new study details observations of low-mass stars forming within reach of the galactic center. The findings lend support to the argument that "adult" stars observed in this region formed near the black hole.

The new evidence for ongoing star formation near the black hole is "a nail in the coffin" for the theory that the stars form in situ, said lead author Farhad Yusef-Zadeh, of Northwestern University. The observations, if accurate, make it unlikely that the stars migrated from elsewhere, the researchers said.

Birth Near a Black Hole

Stars are born within clouds of dust and gas. Turbulence within these clouds give rise to knots that begin to collapse under their own weight. The knots grows hotter and denser, rapidly becoming protostars, which are so-named because they have yet to start fusing hydrogen into helium.

But a protostar can rarely be seen. It has yet to generate energy via nuclear fusion, and any faint light it does produce is often blocked by the disk of gas and dust still surrounding it.

So, when Yusef-Zadeh and his colleagues used the Very Large Array in New Mexico to scan the skies near the central supermassive black hole, they didn't spot the protostars but rather the disks of gas and dust surrounding them.

"You could see these beautiful cometary-shaped structures," Yusef-Zadeh told Space.com. Intense starlight and stellar winds from previously discovered high-mass stars had shaped these disks into cometlike structures with bright heads and tails. Similar structures (called bow shocks) can be seen anywhere young stars are being born, including the famous Orion Nebula.

"There is, of course, one big catch here — and that is that the tidal force on the black hole is so strong that it's hard to see how these stars would form," Yusef-Zadeh said. "Many people think that star formation is forbidden near a supermassive black hole. But nature finds a way."

Astronomers have managed to find a way as well. Over the last decade, they've come up with two scenarios, both of which use the nearby black hole to simulate star formation.

In the first scenario, a cloud might break apart in the strong gravitational field and reassemble into a disk that surrounds the black hole. This disk would then form stars in the same way that the disks surrounding young stars form planets. Although this scenario was first proposed in 2005 by Sergei Nayakshin, an astronomer at the University of Leicester in the United Kingdom, it predicts the formation of low-mass stars. Until now, such stars hadn't been discovered in the galactic center.

In the second scenario, a cloud gets stretched into a taffylike streamer. But as this happens, the gravitational tide from the nearby black hole does two different things. "It disrupts in one direction, but it squeezes in another direction," Yusef-Zadeh said. It's this squeezing, or compressing, that would trigger star formation within the long streamer, Yusef-Zadeh added.

Both scenarios explain why stars encircling the monster black hole, called Sagittarius A*, are found in two rings, or disks, as opposed to random placements.

But some astronomers remain cautious.

"The center of our galaxy is a unique and extreme environment very different from our local solar neighborhood and the rest of the Milky Way," said Jessica Lu, an astronomer at the University of Hawaii's Institute for Astronomy. It's therefore crucial that astronomers don't jump to any conclusions.

"While these bow shocks have similar shapes to protostars seen in the nearby Orion cluster, there are other ways to produce these bow shocks around small clumps of gas," Lu told Space.com in an email.

A Place for Planets

Some scientists who do think that stars — even low-mass stars — are forming within a few light-years of supermassive black holes are now starting to wonder if planets are forming there, too.

Typically, a disk circling a protostar will break up into clumps of gas and dust that later become full-fledged planets. But in such an extreme environment, the wind from nearby stars (the same winds that are responsible for the cometlike shapes of the disks seen by Yusef-Zadeh and his colleagues), may also steal mass from these disks. Yusef-Zadeh and his colleagues estimate that there could be enough material left in those disks to form planets.

Read more at Discovery News

The Milky Way May be 50 Percent Bigger Than Thought

A ring-like filament of stars wrapping around the Milky Way may actually belong to the galaxy itself, rippling above and below the relatively flat galactic plane. If so, that would expand the size of the known galaxy by 50 percent and raise intriguing questions about what caused the waves of stars.

Scientists used data collected by the Sloan Digital Sky Survey to reanalyze the brightness and distance of stars at the edge of the galaxy. They found that the fringe of the disk is puckered into ridges and grooves of stars, like corrugated cardboard.

“It looks to me like maybe these patterns are following the spiral structure of the Milky Way, so they may be related,” astronomer Heidi Newberg, with Rensselaer Polytechnic Institute in New York, told Discovery News.

She and colleagues suspect that a dwarf galaxy may have plunged through the disk of the Milky Way, setting off ripples, like a pebble falling into a pond.

Intruder galaxies also may have set up spiral wave patterns that later trigger star formation in the gas along waves, leading to spiral arms in galaxies.

Evidence that the so-called Monoceros Ring, located more than 65,000 light years from the center of the galaxy, actually is part of the Milky Way surprised Newberg, who was on a team that discovered the ring in 2002.

“We thought it was a tidal debris stream -- a dwarf galaxy that came in and spread itself out in this big ring. For 15 years, there’s been a controversy in the field where half the astronomers think it’s a tidal stream and half the astronomers think its something in the disk. I was in the stream camp,” Newberg said.

“What I was trying to do was find more evidence that it was streams. It took a very long time to get this result, partly because I had to change my whole my whole way of thinking. It now looks to me like it’s part of the disk,” she said.

Incorporating the ring into the map of the Milky Way expands the galaxy’s span from 100,000 light years to 150,000 light years, said astronomer Yan Xu, with the National Astronomical Observatories of China and a former visiting scientist at Rensselaer.

Light travels at 186,000 miles per second, so one light year is nearly 6 trillion miles.

Read more at Discovery News