Tag Archives: black hole

Astronomers Solve Mystery Of Strange Object At The Center Of The Milky Way

G2, a mysterious object near the supermassive blackhole at the center of the galaxy, hosts what was once a pair of stars that have been merged by the enormous gravitational influence of their near neighbor.

Strange things happen at the center of galaxies. Black holes millions of times the mass of the sun produce enormous gravitational forces and emit x-rays. Stars crowd so close together, they are in danger of bumping into each other. Ionized streams of gas light up like auroras.

Yet even in such an intense environment, G2 is something special. It has puzzled astronomers, who initially suspected it of being a gas cloud approaching Sgr A*, the black hole at the galaxy’s center. Debate raged as to how much of it would survive the encounter

However, UCLA’s Professor Andrea Ghez challenged the assumption on which these ideas are based. G2, she argues in The Astrophysical Journal Letters, is not a gas cloud of roughly three Earth masses, as others have speculated, but instead contains a central star, one she suspects of a very interesting history.

Ghez’s conclusions are based on observations of G2 as it reached its closest approach (periapse) to Sgr A* in the course of its orbit. This happened earlier this year when G2 reached a distance of 3000 times the event horizon from Sgr A*. “It was one of the most watched events in astronomy in my career,” says Ghez.

A gas cloud lacking a central object, “should be tidally disrupted during periapse passage,” Ghez and her co-author’s suggest. However, using the 10m Keck telescopes and laser guide star adaptive optics to adjust for the effects of the Earth’s atmosphere, the authors found G2’s brightness and size remained the same and its orbital characteristics were consistent with a condensed object.

They propose the center of G2 is a star. “This star has a luminosity of ~30L? and is surrounded by a large (~2.6 AU) optically thick dust shell,” they argue.

Stars 30 times the brightness of the sun are not unusual; Vega and Sirius are a little above and below that respectively. However, Ghez says although we cannot see it directly, the team believe G2’s star is distinctive for its expansive size, the product of two stars merging together. This prompts an expansion that lasts around a million years before returning to a more normal diameter. 

“This may be happening more than we thought. The stars at the center of the galaxy are massive and mostly binaries,” syas Ghez. “It’s possible that many of the stars we’ve been watching and not understanding may be the end product of mergers that are calm now.”

The combination of the dense packing of stars at the galactic center, and the influence of Sgr A*’s gravity could cause stars to collide and join on a regular basis in a way that almost never happens in the outer reaches of the galaxy. G2’s collision occurred recently enough for us to see the process in action.

Read more: http://www.iflscience.com/space/solution-mystery-galaxys-heart

GRAVITY Instrument Prepares To Observe Our Galaxy’s Black Hole

A new instrument designed to observe regions near black holes is almost up and running and we can expect its first spectacular viewslater this year.

The instrument is called GRAVITY, and it has been installed on the European Southern Observatorys (ESO) Very Large Telescope (VLT) in Chile. It creates a virtual telescope 200 meters (660 feet) across by combining light from multiple telescopes at the VLT site, via a process called interferometry.

GRAVITY will be used to study the extremely strong gravitational fields that exist close to the supermassive black hole at the center of our galaxy, named Sagittarius A*. Specifically, it will look towards the event horizon the theoretical boundary to the inner black hole where gravity is so strong that nothing, not even light, can escape.

The instrument will also observe mass accretion around supermassive black holes, which is the process of material getting pulled in and swirling around in a superheated disc. GRAVITY will also be able to study this process occurring at newborn stars.

Where GRAVITY excels over other instruments is that it can make observations for several minutes, which is more than a hundred times longer than previously possible. GRAVITY will open optical interferometry to observations of much fainter objects, and push the sensitivity and accuracy of high angular resolution astronomy to new limits, far beyond what is currently possible, said Frank Eisenhauer of the Max Planck Institute for Extraterrestrial Physics in Germany, who led the installation of the instrument.

Shown is the GRAVITY instrument at the VLT in Chile.ESO/GRAVITY consortium

The instrument has already made its first observations, looking at the bright, young stars of the Trapezium Cluster. And it even made a discovery, finding that one component of the cluster was a previously unknown double star.

This observation was made using smaller telescopes at the VLT site, four 1.8-meter (6-foot) Auxilliary Telescopes. Later in 2016, it will use the four 8-meter (26-foot) VLT Unit Telescopes to start probing the regions near our supermassive black hole.

And this isnt the only new black hole-hunting telescope. The Event Horizon Telescope, which will link nine telescopes from across the world, will also start observing Sagittarius A*, sometime in 2017. It is expected to get our first ever views of the black hole itself.

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Read more: http://www.iflscience.com/space/gravity-instrument-prepares-observe-our-galaxys-black-hole

This Image Shows The Most Terrifying Explosion In The Universe

The most powerful black hole ever discovered resides in the galaxy cluster MS 0735.6+7421, 2.6 billion light-years away in the constellation of the Giraffe (Camelopardalis).

It has a mass estimated around 10 billion solar masses, and every second produces the same amount of energy emitted by the Sun every 200,000 years. In its 100 million years of activity, it has emitted1055 Joules of energy, consuming a mass equivalent to 600 million solar masses.

Although discovered in 2005, astronomersare still unsure where all this material came from. Large black holes are expected to have grown very little in the recent past, so scientists are definitely intrigued by this object. A leading theory suggests that the gas in the galaxy suddenly and catastrophically cooled and was swallowed by the black hole. This black hole is feasting when it should be fasting as it was once described.

The monstrous black hole has a dramatic effect on the entire cluster. Materialsbetween the galaxies in the cluster are heated up to 100 million degrees Kelvin and two large cavities, 600,000 light-years across, have been produced by the powerful jets of the black hole.

The jets are made by highly energetic electrons which emitradio waves (the pinkish light in the image above). These electrons move through the hot intergalactic gas at supersonic speed up to a million light-years from their source, forming the seen gaps.

Astronomers were able to estimate the energy of the black holes (among other properties), just by looking at the size of the cavities. The X-ray telescopeChandra, which was used to discover the object, has seen other cavities like these but never of such enormous size.

Thisimage of MS 0735.6+7421 is one of a collection of six images releasedfrom the Chandra Data Archive in early October, which has been collecting datafor16 years, operating asNASA’sX-ray observatory.

Read more: http://www.iflscience.com/space/most-terrifying-explosion-universe

Astronomers Spot A Star Being Ripped Apart By A Black Hole

A team of astronomers has observed stellar debris being flung around a black hole in a (relatively) nearby galaxy.These types of events are called tidal disruptions, and the one reported in this study is the closest detected in the last 10 years.

The galaxy, named PGC 043234, is a small elliptical galaxy about 295million light-years from the Milky Way. The scientists witnessed the consequences of a star passing too close to a central black hole within PGC 043234; the strong gravitational forces around the black hole shredded the star apart, sucking most of the materialbeyond the event horizon (the point of no return around a black hole)while flinging some of it outwards into a wider orbit around the black hole.

The tidal disruption was first observed in optical light by the All-Sky Automated Survey for Supernovae (ASAS-SN), then quickly followed with NASA’s Chandra X-ray Observatory, NASA’s Swift Gamma-ray Burst Explorer and the ESA’s XMM-Newton satellite.

Materials around black holes tend to have a strong X-ray signature. As the stellar material falls towards the black hole, it forms an accretion disk; the acceleration and the friction within the disk, due to the immense gravitational pull, is enough to generate a substantial amount of X-rays. The accretion disk can reach temperatures of 10 million degrees, according to some studies.

“We have seen evidence for a handful of tidal disruptions over the years and have developed a lot of ideas of what goes on,” said lead author Jon M. Miller, a professor of astronomy at the University of Michigan, in a statement. “This one is the best chance we have had so far to really understand what happens when a black hole shreds a star.”

The formation of accretion disks has remained a mystery, but the observation of this event allowed the team to witness how such disks come to be. Scientists have been studying tidal disruptions for three decades, but this is the first detailed close-up of one.

The black hole, called ASASSN-14li, is believed to have the mass of 2 million Suns, making it about half the size of the Milky Ways own supermassive black hole, Sagittarius A*.

The study was published in the October 22, 2015, issue of the journal Nature.

Read more: http://www.iflscience.com/space/astronomers-saw-star-ripped-apart-black-hole

Rare Double Star System Seen In Final Death Throes Before It Explodes

An incredible stellar system has been found where two stars are so close that their surfaces are overlapping. It is the hottest and most massive double star system ever seen, and provides a rare glimpse into what is believed to be a relatively brief cosmic event.

The system is known as VFTS 352, found 160,000 light-years away in the Tarantula Nebula by the European South Observatory’sVery Large Telescope. Both of the stars are nearly identical in size, with a combined mass 57 times greater than the Sun, meaning one is not sucking material from the other rather, they are likely sharing 30% of their material. This has led to a bridge forming between their two connected surfaces.

The two stars, classed as O-type stars that shine blue-white, have surface temperatures of more than 40,000degrees Celsius(72,000degrees Fahrenheit), and complete an orbit of each other in just one Earth day. Double systems like this may be the main source of certain elements such as oxygen in the universe.

Their centers are separated by a mere 12 million kilometers (7.5 million miles), and the intense tidal forces (the gravitational pull of one star on the other) are thought to be mixing the material in their interiors. The VFTS 352 is the best case yet found for a hot and massive double star that may show this kind of internal mixing, said lead author Leonardo Almeida from the University of So Paulo, Brazil in a statement. As such its a fascinating and important discovery.

What will happen next to the stars is especially interesting. Its possible that the two may combine into a single giant star in 600,000 years that would spin extremely rapidly, and ultimately end in a huge explosion up to four million years later known as a long-duration gamma-ray burst, one of the most explosive events in the universe.

The other possibility is that the two will go supernova separately in about three million years, both becoming black holes but continuing to orbit one another, forming a binary black hole system. Such a remarkable object would be an intense source of gravitational waves, Selma de Mink of the University of Amsterdam, the lead theoretical astrophysicist on the team, said in the statement.

Whatever happens, this system is proving to be a fascinating insight into a rare and ethereal phenomenon.

Read more: http://www.iflscience.com/space/rare-double-star-system-seen-final-death-throes-it-explodes

Astronomers Think They’ve Found The Second-Largest Black Hole In The Milky Way

There are thought to be three types of black holes out there, each a different sized, star-swallowing, spacetime-warping colossus. A new study published in The Astrophysical Journal Letters claims to have discovered a fourth intermediary type hiding within our very own galaxy.

The first type of black holes, stellar black holes (SBHs), appearwhen extremely massive stars, having reached the end of their lives, are no longer able to perform nuclear fusion. The inwardly directed gravitational force of the star overcomes the externally directed generation of heat, and a catastrophic implosion occurs. The resulting SBH typically has a massof around ten Suns (solar masses).

The second type, primordial black holes, are purely hypothetical at this stage. Formed by the compaction of matter present during the universes early expansion, they could be as small as a single atom, but with the mass of a large mountain.

Supermassive black holes (SMBHs) are typically found at the hearts of galaxies, and are easily the most gargantuan. Our Milky Way’sSagittarius A*, for example,is four million times more massive than the Sun. Their formation mechanism is still open to debate: Some scientists think that they grow by absorbing smaller black holes over time, whereas others believe they form from the collapse of enormous gas clouds early on during the galaxy formation.

The problem with this three-tiered categorization is that there isnt much room for intermediate-mass black holes or IMBHs those with masses somewhere between that of a SBH and a SMBH. In 2014, the discovery of one such black hole was claimed: A luminous object called X-1 in the constellation M82, with 400 solar masses, was spotted, and astronomers declared it an IMBH.

The SMBH, Sagittarius A*, at the core of the Milky Way, seen with respect to the new IMBH candidate, highlighted in magenta. The scale bar is in parsecs, where one parsec equals 3.26 light-years. Oka et al./The Astrophysical Journal Letters

Its mass was calculated by looking at the X-ray emissions jettisoning from it. Astronomers noticed that these emissions seem to beat like a drum, appearing at set 3-2 ratios for example, 300 times per second and then 200 times per second. The frequency of these beats are inversely proportional to the mass of the black hole, so an emission rhythm of 150 times per second then 100 times per second would be coming from a more massive black hole than one with a 300-200 beat. X-1 had a rhythm of roughly 5-3.3 X-ray emissions per second, meaning that it had a mass of 428 Suns, making it an IMBH.

This more recent study wasnt actually looking for IMBHs, but was instead peering at an enigmatic gas cloud called CO-0.40-0.22. Using Japans Nobeyama and Chiles ASTE radio telescopes, the researchers noticed that the gas molecules in the cloud were all moving at a wide range of speeds, meaning something was accelerating them. X-ray observations, like those used to look at X-1, revealed nothing.

However, a simulation of the gas movement in the cloud suggested only one culprit: namely, an IMBH of around 100,000 solar masses is hiding in the cloud, using its powerful gravitational field to fling particles chaotically through space. If proven to be true by independent studies, this IMBH will be the first of its kind: it, and its gas cloud shield, are both within our own Milky Way. It will also be the second most massive black hole in our galaxy, after Sagittarius A*.

However, a controversy now exists. X-1 was detected using powerful X-ray emissions, and this new IMBH candidate was not. And since there is no reference IMBH for comparison,that these two studies therefore sharply disagree on which one, if any, is actually an IMBH.

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Read more: http://www.iflscience.com/space/have-astronomers-found-milky-ways-second-most-massive-black-hole

Magnetar Formation: It’s A Game Of Pass The Parcel

Using the world’s most advanced optical instrument, the ESO’s Very Large Telescope (VLT), astronomers have made a discovery which could help shed light on something that has puzzled scientists for decades: how magnetars form.

When the life of a massive star comes to an end and it explodes dramatically as a supernova, either a neutron star or black hole is formed. A magnetar is a rare and extremely unusual type of fast-spinning neutron star. They’re tiny yet incredibly dense; a mere teaspoon of magnetar material would have a mass of around a billion tonnes. They’re also the most powerful magnets known to exist in the entire universe, but the mechanism behind their formation has been shrouded in mystery.

In an attempt to find out more about these enigmatic objects, astronomer Simon Clark of the Open University, U.K., and colleagues turned to a star cluster known as Westerlund 1. This young cluster, which is found 16,000 light-years away from us within a constellation called Ara, contains one of the few known magnetars in the Milky Way called CXOU J164710.2-455216.

According to Clark, this magnetar was puzzling since they had previously demonstrated that it formed from the explosion of a star around 40 times as massive as our Sun. This left the team scratching their heads since the explosion of a star this massive should result in a black hole.

The team hypothesized that this magnetar could have formed through interactions with another massive star, but prior to this study no companion star was discovered that fitted the bill. However, the astronomers managed to identify a blue supergiant star that they postulate may have once orbited the star that was destined to become the magnetar. This highly luminous star, named Westerlund 1-5, appeared to be fleeing Westerlund 1 at a high velocity, as would be expected if it had been flung out of orbit by the supernova explosion.

In a report published in Astronomy & Astrophysics, the scientists describe the likely series of events that led up to the formation of the magnetar. As Westerlund 1-5 started to run out of fuel, it began to unload a substantial amount of its gas onto its smaller companion star, causing it to spin faster. According to the scientists, this dramatic increase in rotation was responsible for the increase in the star’s magnetic field.

As the partner star grew in size it reached a stage where it became so massive that it then started to cast off a substantial amount of its mass, some of which was passed back to Westerlund 1-5. This loss of mass was critical since if the star exploded when it was extremely massive it would have collapsed into a black hole.

In support of this second mass transfer, Westerlund 1-5 was found to have an unusual chemical composition. In particular, they found that was rich in carbon when it shouldn’t be. The team believe that shortly before its demise, the pre-magnetar star burned helium into carbon and shed this carbon onto Westerlund 1-5.

“It is this process of swapping material that has imparted the unique chemical signature to Westerlund 1-5 and allowed the mass of its companion to shrink to low enough levels that a magnetar was born instead of a black hole- a game of stellar pass-the-parcel with cosmic consequences!” said Francisco Najarro, one of the authors of the study.

Although this work is not definitive, it could serve as a reasonable theory to explain how at least some of these perplexing super magnets come into existence. 

Read more: http://www.iflscience.com/space/magnetar-formation-its-game-pass-parcel

Black Holes May Collapse Into Their Exact Opposites: White Holes

Despite its name, a black hole is not an empty void. Most black holes form when stars die in a supernova explosion, collapsing under their own gravity. When a star 10 times more massive than the sun dies in a supernova, for example, its mass can be squeezed into a ball with the diameter of New York City. The resulting gravitational field is so strong not even light can escape.

For decades, astrophysicists have wondered whether black holes destroy information — meaning what falls into them is lost forever. A new model suggests that at the end of their lives, black holes turn into “white holes,” explosively pouring all the material they have ever swallowed into space, Nature reports

According to the new model, developed by Carlo Rovelli and Hal Haggard from Aix-Marseille University in France, the transformation from a black hole to a white hole would occur right after the initial formation of the black hole. Their model is based on a theory called “loop quantum gravity” — where gravity and space-time are quantized, woven from tiny-individual loops that can’t be subdivided any further. 

As a dying star collapses under its own gravity, it’s surrounded by a boundary called the event horizon: the point of no return, past which nothing can escape the black hole’s gravity. The star will continue to shrink, but eventually it will reach a stage where it can’t get any smaller because the loops cannot compress anymore. 

At this point, the loops exert an outward pressure called “quantum bounce,” which transforms the black hole into a white hole. According to the team’s rough estimates, it takes just a few thousandths of a second for a black hole to transform into a white hole. Yet even though the transformation is nearly instantaneous, the researchers say, black holes can still appear to us as lasting billions or trillions of years because their gravity stretches light waves and dilates time.

If that’s the case, then rather than being shrouded by a true, eternal event horizon, black holes would be concealed by a temporary “apparent horizon,” Rovelli says. That’s important, because a true event horizon might violate the laws of physics.

In the 1970s, Stephen Hawking of the University of Cambridge calculated that a black hole should emit radiation out of its event horizon, slowly losing energy and shrinking in the process until it completely disappears. But that means information carried by matter falling into black holes would vanish forever. “There is no escape from a black hole in classical theory,” the famed physicist told Nature earlier this year, “but quantum theory enables energy and information to escape.”

Having black holes turn into white holes could solve one of fundamental physics’ most troublesome questions. Their work is available at arXiv. 

[Via Nature]

Read more: http://www.iflscience.com/space/black-holes-may-collapse-their-exact-opposites-white-holes

Black Holes Burp Might Help In Forming New Stars

Black holes are thought to be world destroyers, but some new evidence suggests that in some cases, they can actually help in the formation of stars.

In the findings, made by the Chandra X-ray Observatory andpresented yesterday at the 227thMeeting of the American Astronomical Society, researchers highlighted the dramatic feedback mechanisms between a galaxy and its supermassive black hole. Thisblack hole has been observed producing outbursts of material, which are compressing gas, and astronomers believe it will induce new star formation.

The galaxy, called M51b, is the small companion of the more famous Whirlpool galaxy. Its a small elliptical galaxy that is slowly being assimilated by its larger spiral companion. When galaxies merge, the strong forces produce intense episodes of star formation and as the gas moves around, the supermassive black holes at their center wake up and start gorging on whatever is around them.

The more material around a black hole, the more energy the black hole releases. This energy creates galactic winds thatthen snuff out potential new stars. This feedback between galaxies, stars, and black holes regulates how a galaxy evolves during a merger.

“We think that feedback keeps galaxies from becoming too large,” said Marie Machacek, a coauthor of the study from the Harvard-Smithsonian Center for Astrophysics (CfA), in a statement.”But at the same time, it can be responsible for how some stars form. This shows that black holes can create, not just destroy.”

The team has detected two enormous arcs of material glowing in X-rays, which were emitted by the black holes several million years ago. Observing the region outside the arcs, they saw cool hydrogen, which is the necessary component for stars to form. The arcs have been plowing material from the center of the galaxy to the outskirts, and now the material is dense enough and cool enough to trigger star formation.

M51b, seen top left, is a companion of the larger Whirlpool Galaxy.NASA/CXC/Univ of Texas/STScI/E.Schlegel et al

Due to their position in the galaxy, the researchers think this is a rare view of the intermediate stage of the feedback process.

“For an analogy, astronomers often refer to black holes as ‘eating’ stars and gas.Apparently, black holes can also burp after their meal,” said Eric Schlegel of The University of Texas in San Antonio, who led the study.

“Our observation is important because this behavior would likely happen very often in the early universe, altering the evolution of galaxies. It is common for big black holes to expel gas outward, but rare to have such a close, resolved view of these events.”

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Read more: http://www.iflscience.com/space/black-hole-s-burp-might-help-forming-new-stars

What’s Causing These Mysterious Radio Bursts From Beyond Our Galaxy?

Neutron stars are so dense that not even black holes can tear them apart. When one falls into a black hole, the black hole swallows it whole. Without material being disrupted, we have a hard timeto tell such an event has taken place. At least until now.A new study has claimed that extremely powerful fast radio bursts (FRBs) are generated in the last instantbefore a neutron star collides with a black hole.

FRBs are incredibly powerfulemissions of radio waves lasting only for a few milliseconds. The first was discovered in 2007, in archived data from the Parkes radio telescope in Australia. So, far only 11 have been discovered and only one of them was discovered live. The discovery of that eventwas quickly followed up by observations of the samearea in many different wavelengths, but they couldnt see any object responsible for the FRB.

The new research, which will be published in the Astrophysical Journal Letters, describes how the FRB could be powered by a gigantic cosmic battery. When black holes and neutron stars orbit very close together, the strong magnetic fields of both objects link, and as the objects rotate,plasma flows along the magnetic field lines generating an electric currentbetween them. The closer they get, the stronger the current becomes and when the objects merge, the electricity is released in a sudden burst of radio waves.

According to the study, high sensitivity radio telescopes should be able to observe an increase in the intensity of radio wavesbefore the final FRB, as well as detectinga second burst when the magnetic field of the neutron star moves onto the black hole.

Black holes and neutrons stars are two possible ways a star could endafter it goes supernova. Only the biggest stars turn into black holes. Scientists are interested in black hole-neutron star pairs as they should be emitting a lot of gravitational waves.

“In the event of aneutron star-black hole gravitational wave detection, a coincident electromagnetic detection, such as an FRB, may be possible with atelescope such as CHIME, which is optimally located with respect to the LIGO detectors.”DrChiara Mingarelli, lead author of the study, told IFLScience.”CHIME, in fact, predicts that they may detect up to 10,000 FRBs per year.”

This study doesnt claim that neutron star-black holebinariesexplain every single FRB event, but they are probably the cause ofa fraction of them. Curiously, some events that looked like FRBs, called perytons, are actually produced by people opening the door of their microwave oven before the timer has got to zero.

Read more: http://www.iflscience.com/space/black-holes-colliding-neutron-stars-could-power-unusual-radio-bursts-0