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Astronomers Use Hubble To Capture Extremely Bright Galaxies

June 22, 2017 by  
Filed under Around The Net

A glittering jackpot of ultrabright galaxies bursting with star formation has been revealed in a series of stunning images taken by the Hubble Space Telescope.  

The galaxies captured in these images sparkle like jewels of cosmic light. These massive collections of stars are each as much as 10,000 times more luminous than the Milky Way in the infrared range, or 10 trillion to 100 trillion times the brightness of the sun. They are also forming about 10,000 new stars each year, according to a statement from NASA. (By comparison, it is estimated that fewer than 10 stars form in the Milky Way each year.)

Viewers may also notice strange shapes, including rings and arcs of light. Those are mostly the result of a cosmic phenomenon known as gravitational lensing, in which a foreground galaxy acts as a lens, warping and magnifying the light from a more distant galaxy

This lensing has magnified the light from these very distant galaxies, giving scientists the opportunity to study in them in much finer detail than would be otherwise possible. 

“These ultra-luminous, massive, starburst galaxies are very rare,” James Lowenthal, an astronomy professor at Smith College in Massachusetts and lead researcher on the Hubble survey, said in the statement. “Gravitational lensing magnifies them so that you can see small details that otherwise are unimaginable. We can see features as small as about 100 light-years or less across. We want to understand what’s powering these monsters, and gravitational lensing allows us to study them in greater detail.”

The birth and death of so many stars generate a lot of new gas and dust, which obscures the galaxies in many wavelengths of light, including visible. But infrared light can penetrate those layers. These galaxies were first identified by the European Space Agency’s Planck satellite, and were subject to further study by other instruments, but the Hubble observations confirmed that gravitational lensing is making them brighter and more visible. 

The furious star formation in these galaxies coincides with the “peak of the universe’s star-making boom between 8 billion and 11.5 billion years ago,” according to the statement. Even so, only a few dozen of these star-forming, bright infrared galaxies existed in that period of the early universe, NASA said. 

In the nearby universe, researchers have identified so-called ultra-luminous infrared galaxies (ULIRGS), which are also massive, cloaked in dust, and have high rates of star formation. The star formation in those galaxies is “stoked by the merger of two spiral galaxies,” according to the statement. Such a collision could have brought together large amounts of gas and dust into a relatively small region, creating an environment ripe for star formation. 

But it’s not clear if similar galaxy mergers were taking place between 11.5 billion and 8 billion years ago, so scientists aren’t sure if the galaxies seen in this recent Hubble survey are fueled by the same mechanism as the nearby galaxies. 

“The early universe was denser, so maybe gas is raining down on the galaxies, or they are fed by some sort of channel or conduit, which we have not figured out yet,” Lowenthal said. “This is what theoreticians struggle with: How do you get all the gas into a galaxy fast enough to make it happen?”

To unlock the mysteries these galaxies may hold, scientists need to know if the strange features that appear in the Hubble images — the curves and arcs of light — are artificial features generated by the lensing effect, or if they are indicative of actual features around the galaxies. The researchers now need to separate artifice from reality to come up with some answers.

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Astronomer Find The Building Blocks Of Life Found Around Baby Star

June 21, 2017 by  
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The young, triple-star system IRAS 16293-2422 is located approximately 400 light-years from Earth in the constellation of Ophiuchus. The infant stars in this system have a similar mass to the sun, but are still in the early stages of formation. 

Researchers have detected a complex organic molecule called methyl isocyanate near the stars. This is the first time that the molecule, which can be a precursor to life, has been found around sun-like protostars, according to a statement from the European Southern Observatory (ESO). [6 Most Likely Places for Alien Life in the Solar System]

Previously, astronomers found a simple form of sugar in the disk of gas and dust surrounding IRAS 16293-2422. The sugar, called glycolaldehyde, is linked to the formation of RNA, which is one of the building blocks of life. 

“This star system seems to keep on giving! Following the discovery of sugars, we’ve now found methyl isocyanate,” Niels Ligterink and Audrey Coutens, researchers at the Leiden Observatory in the Netherlands and University College London, respectively, said in the statement. “This family of organic molecules is involved in the synthesis of peptides and amino acids, which, in the form of proteins, are the biological basis for life as we know it.” Ligterink and Coutens make up one of two teams of astronomers who detected the new molecule; the findings are detailed in two studies that will be published in the Monthly Notices of the Royal Astronomical Society.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile, the astronomers found signatures of methyl isocyanate molecules in the inner regions of the dust and gas surrounding each of the stars, according to the ESO statement. “We are particularly excited about the result because these protostars are very similar to the sun at the beginning of its lifetime, with the sort of conditions that are well suited for Earth-sized planets to form,” Rafael Martín-Doménech and Víctor M. Rivilla, co-lead authors of the second study, said in the statement. “By finding prebiotic molecules in this study, we may now have another piece of the puzzle in understanding how life came about on our planet.”

Earth and other planets in the solar system formed from material left over after the formation of the sun. Therefore, studying young, sun-like stars like IRAS 16293-2422 can help astronomers learn more the early years of our solar system.

In addition to the ALMA data, both teams of researchers used computer chemical modeling to better understand the origin of the methyl isocyanate molecules.

Models suggest that the molecules likely formed on “icy particles under very cold conditions that are similar to those in interstellar space,” Ligterink said. 

“This implies that this molecule — and thus the basis for peptide bonds — is indeed likely to be present near most new young solar-type stars,” he added. 

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Einstein’s Theory Used To Calculate The Mass Of A Star

June 16, 2017 by  
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The mass of Stein 2051 B, a white dwarf star located about 18 light-years from Earth, has been a subject of some controversy for over a century. Now, a group of astronomers has finally made a precise measurement of the star’s mass and settled a 100-year-old debate, using a cosmic phenomenon first predicted by Albert Einstein. 

The researchers calculated the star’s mass using carefully timed observations made by the Hubble Space Telescope, which studied Stein 2051 B when it eclipsed another, more distant star, as seen from Earth. During this transit, the background star appeared to change its position in the sky, moving ever so slightly to the side, even though its actual position on the sky had not changed at all. 

This cosmic optical illusion is broadly known as gravitational lensing, and its effects have been observed extensively throughout the universe, especially near very massive objects, such as entire galaxies. The effect occurs because a massive object warps the space around it and acts like a very large lens, bending the path of the light from the more distant object. In some cases, this creates the illusion that the background star has been displaced. 

(Water can also create this kind of displacement illusion; try placing a pencil in a glass of water, and note that the submerged half of the pencil appears disconnected from the dry half.)  

Einstein predicted that these displacement events could be used to measure individual stellar masses. That’s because the extent to which the background star’s position is offset depends on the mass of the foreground star. But telescopes at the time lacked the sensitivity to make that dream a reality. 

The scientists behind the new work said no one, before now, has ever used the displacement of a background star to calculate the mass of an individual star. In fact, there is only one other example of scientists measuring this displacement between individual stars: During the 1919 total solar eclipse, scientists saw the sun displace a few background stars. That measurement was possible only because of the sun’s proximity to Earth. 

A paper describing the new work was published online today in the journal Science.

Einstein’s theory of general relativity hypothesized that space is flexible rather than fixed, and that massive objects (like stars) create curves in space, sort of like a bowling ball creating a curve on the surface of a mattress. The degree to which an object warps space-time depends on how massive that object is (similarly, a heavier bowling ball puts a deeper imprint on a mattress).

A ray of light normally travels in a straight line through empty space, but if the ray passes close by a massive object, the curve in space created by the star acts like a bend in the road, causing the light ray to veer away from its formerly straight path. 

Einstein showed that this deflection could direct more light toward the observer, similar to how a magnifying glass can focus diffuse light from the sun down into a single spot. This effect causes the background object to appear brighter, or it creates a ring of bright light around the foreground object called an Einstein ring.  

Astronomers have observed Einstein rings and “brightening events” when very massive foreground lenses, like entire galaxies, create the phenomena. These have also been observed along the plane of the Milky Way galaxy, where individual stars likely cause the lensing effect. It has also been used to detect planets around other stars.  

In the new study, astronomers reported the first ever observation of so-called “asymmetric lensing” involving two stars outside Earth’s solar system, in which the position of the background star appeared to change. 

The degree of displacement is directly related to the foreground object’s mass. With relatively “light” objects, like stars, the displacement is extremely small and thus more difficult to detect, according to Kailash C. Sahu, an astronomer at the Space Telescope Science Institute in Baltimore, and the lead author on the new paper. In the case of Stein 2051 B, the displacement was about 2 milliarcseconds on the plane of the sky, or about equal to the width of a quarter seen from 1,500 miles (2,400 kilometers) away, Sahu said.

Measuring such a subtle change required a powerful instrument, like the Hubble telescope’s high-resolution camera, which was installed in 2009. This instrument also made it possible to pick out the light from the displaced star, which was somewhat overshadowed by the light from Stein 2051 B — like a firefly next to a lightbulb, Sahu said. 

The researchers took eight measurements between October 2013 and October 2015, so they could observe the white dwarf moving across the sky, eclipsing the background star and creating the displacement. The scientists also observed the actual position of the background star after the white dwarf had passed by. 

Many variables could affect whether scientists can observe more events like this. Those variables include the alignment of the two objects, the mass and proximity of the foreground object, the separation between the foreground and background object, and the sensitivity of the telescope. But Sahu said he thinks his team has demonstrated the effectiveness of the method and that scientists could use it to measure the masses of about two to four nearby stars per year. 

White dwarfs are stars that have stopped burning hydrogen in their cores and subsequently shed their outer layers. In each of these stars, the remaining mas has collapsed into a dense core known as a white dwarf. This collapse drives up the temperature on the surface of these objects, so they may burn hotter than “living” stars. 

“At least 97 percent of the stars in the sky, including the sun, will become or already are white dwarfs,” Terry Oswalt, a professor of engineering and physics at Embry-Riddle Aeronautical University in Daytona Beach, Florida, wrote in an accompanying Perspectives article in Science. “Because they are the fossils of all prior generations of stars, white dwarfs are key to sorting out the history and evolution of galaxies such as our own.”

The mass of Stein 2051 B has been “a source of controversy for over 100 years,” said Oswalt, who was not affiliated with the new research. 

The current picture that scientists have of white dwarfs suggests that the mass and radius of these objects reveals important information about how they formed, what they’re made of, and what kind of stars they formed from, according to Sahu. 

Previous measurements of the mass of Stein 2051 B suggested it was largely composed of iron, but that finding presented several problems based on accepted theories about white dwarf formation and stellar evolution, according to the research paper. For example, to form large amounts of iron, the star that would become Stein 2051 B would have to have been extremely massive, but the radius of Stein 2051 B suggests it formed from a star not much larger than the sun. 

If those measurements of Stein 2051’s mass were correct, it would have sent astrophysicists back to the drawing board to figure out how such an object could have formed. Sahu said astronomers realized their measurements of Stein 2051 B’s mass were probably incorrect, but they had no way to know for sure.  

Typically, the only way to measure the mass of a star is to observe how it interacts with another massive body. For example, in a binary system where two stars orbit each other, the heavier star will have a large influence on the motion of the lighter one, and by observing the two stars’ interaction over time, scientists can calculate more and more specific values for the stars’ masses. Stein 2051 B has a companion, but the two bodies orbit very far apart, so their influence on each other is minimal. 

The new result shows that Stein 2051 B is in fact a very normal white dwarf, and it fits in just fine with the accepted formation theory Sahu said. Its mass is about 0.68 times the mass of the sun, indicating it formed from a star about 2.3 times the mass of the sun, Sahu said. That’s compared to the previous measurement which placed the white dwarf’s mass at about 0.5 times the mass of the sun. Not very many white dwarfs have had both their masses and radii measured precisely, he added .

“It confirms white dwarf mass-radius relationship,” he said. “[Astrophysicists] have been using that theory, and it’s good to know it’s on solid footing.”

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Astronomers Discover 3rd Black Hole Merger

June 13, 2017 by  
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It’s not a fluke: For the third time, scientists have detected ripples in space-time caused when two black holes circle each other at mind-bending speeds and collide.

The LIGO gravitational-wave detector spotted the space-time ripples on Jan. 4, members of the LIGO Scientific Collaboration announced today (June 1).

If this news sounds familiar, it’s because this is the third black-hole collision that LIGO has detected in less than two years. These three consecutive discoveries signal to astrophysicists that mergers between black holes in this mass range are so common in the universe that LIGO may detect as many as one per day when the observatory begins operating at its full sensitivity, members of the collaboration said during a news teleconference yesterday (May 31). 

“If we’d run for a long time and hadn’t seen a third black-hole merger … we would have started scratching our heads and saying, ‘Did we just get really lucky that we saw these two rare events?'” David Reitze, LIGO Laboratory executive director and a professor of physics at the California Institute of Technology, told Space.com. “Now I think we can say safely that that’s not the case. I think that’s exciting.”

A batch of black-hole detections by LIGO could help scientists learn how black holes of this size — those with masses tens of times that of the sun, or so-called stellar-mass black holes — are born, and what causes them to come together and merge into a new, single black hole. A paper describing the new discovery includes a few clues about the spins of the original two black holes, which is an early step in learning about the environment where they formed and how they ended up colliding.  

Ripples in space-time

LIGO (which stands for Laser Interferometer Gravitational-Wave Observatory) was the first experiment in history to directly detect gravitational waves — ripples in the universal fabric known as space-time that were first predicted by Albert Einstein. The famous physicist showed that space and time are fundamentally linked, such that when space is distorted, time can either slow down or speed up.

Although LIGO first began taking data in 2002, it wasn’t until the observatory underwent a major upgrade, called Advanced LIGO, that it achieved the sensitivity necessary to make a detection. The first black-hole merger spotted by LIGO was announced in February 2016; the second was announced in June 2016.

This new merger spotted by LIGO took place between one black hole with a mass about 19 times that of the sun, and another with a mass about 31 times that of the sun. Those companions combined to form  a new black-hole with a mass of about 49 times that of the sun (some mass can be lost during the merger). The entire mass of that final black hole is packed into an object with a diameter of about 167 miles (270 kilometers), or about the width of the state of Massachusetts, according to the LIGO scientists.

This newly-formed black hole falls between the final masses of the black holes that LIGO previously detected, which were 62 solar masses and 21 solar masses.

The gravitational waves created by this new black hole collision had to travel across the universe for 3 billion years before they reached Earth. That means this new black hole merger occurred more than twice as far away from Earth as the first and second  black hole mergers detected by LIGO. The gravitational waves from those black hole collisions traveled for 1.3 billion and 1.4 billion years to reach Earth, respectively.

This map of the night sky shows the location of three confirmed black hole mergers detected by the LIGO gravitational wave experiment, as well as a fourth , unconfirmed event. The most recent detection is labelled GW170104. LIGO can only locate the source of a gravitational wave signal to a fairly large area on the sky. When more gravitational wave detectors come online, those experiments will be able to help LIGO narrow down the source of a signal.

Credit: LIGO/Caltech/MIT/Leo Singer (Milky Way image: Axel Mellinger)

However, as with the previous two detections, the LIGO detector can’t determine precisely where the newly formed black hole is located. Rather, the data only narrows down the source of the signal to an area of about 1,200 square degrees. (See the map of the sky above to see the area from which the signal could have come.)

Because black holes don’t radiate any light of their own (or reflect light from other sources), they are effectively invisible to light-based telescopes, unless regular matter nearby creates a secondary source of light. Black holes with masses between 20 and 100 solar masses aren’t expected to have much, if any, regular matter around them radiating light, and black holes in this mass range hadn’t been observed by astronomers prior to LIGO’s three discoveries.

But gravitational waves come directly from the black holes. This opens up a new realm of the universe that is visible to an instrument like LIGO, which was designed to detect gravitational waves, but invisible to other telescopes. The three mergers that LIGO detected not only confirm the existence of black holes in this mass range, but also show that they are fairly common throughout the universe, according to the collaboration members.

In the data from the new detection, the LIGO scientists managed to glean a little information about the spin of the two black holes. Those clues could hint at why the black holes wound up crashing into each other, LIGO collaboration members said.

Black holes spin on their axes just as the Earth, most planets and most moons do. Stellar-mass black holes are thought to form when massive stars run out of fuel and collapse. If two massive stars live in a “binary” system, they will typically spin along the same axis, like two tops spinning next to each other on the ground. When those stars become black holes, they will also spin along the same axis, researchers said in a statement from Caltech.

But if the black holes formed in different regions of a stellar cluster and come together later, they may not spin along the same axis. Those misaligned spins will slow the merger, said Laura Cadonati, the LIGO Scientific Collaboration’s deputy spokesperson and an associate professor of physics at the Georgia Institute of Technology.

“In our analysis, we cannot measure spins of individual black holes very well but can tell if they’re generally spinning in same direction,” Cadonati said during yesterday’s news teleconference. The LIGO data doesn’t provide a strong ruling about whether the black-hole spins were aligned or misaligned. The authors of the new research concluded that the data “disfavors” the identical spin alignment of the black-hole axis, according to the paper, which has been accepted for publication in the journal Physical Review Letters.

“This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that binary black holes may form in dense stellar clusters,” Bangalore Sathyaprakash, a researcher at Pennsylvania State University and Cardiff University and one of the LIGO collaboration members who edited the new paper, said in the statement from Caltech.

Of course, black-hole mergers could arise from both scenarios. To get an idea of the most common origin story for solar-mass black-hole mergers, LIGO scientists will need more than three examples to study.

The discovery of three stellar-mass black-hole mergers in less than two years indicates that LIGO will be seeing a lot more of these types of events, Reitze told Space.com. But three events are still not enough to know for sure exactly how frequently LIGO will begin to see these black-hole collisions once its sensitivity is increased. The optimistic estimate that Reitze and other collaboration members cite is one per day, but even the pessimistic estimates are around one per month. That means LIGO could collect data on tens to hundreds of black-hole mergers in three to five years of operations. With this collection of black-hole mergers, scientists will be able to learn about the general population rather than a few individuals.  

A large collection of black holes could also provide scientists with a deeper look at Einstein’s theory of general relativity. Black holes are “pure space-time,” according to Reitze, meaning that while they might have formed from regular matter, their interaction with the universe has none of the properties of regular matter. Rather, the characteristics of a black hole are described entirely in terms of how its gravity warps space-time or influences other objects.

The theory of relativity predicted the existence of space-time and gravitational waves, so LIGO’s detection of this phenomenon was another confirmation that the theory is accurate. But the study of black holes and gravitational waves could also reveal cracks in that theory.

For example, when light waves pass through a medium like glass, they may be slowed based on their wavelength — a process called dispersion. General relativity states that gravitational waves should not be dispersed as they travel through space, and the researchers saw no sign of dispersion in LIGO’s new data.

For now, it seems, Einstein was right. But one of the most exciting things that LIGO could potentially discover is a flaw in the theory, Reitze said. Einstein’s theory of gravity has withstood scrutiny for more than a century, but it also doesn’t match up with the theory of quantum mechanics. The lack of an obvious connection between gravity (which generally describes the universe on very large scales) and quantum mechanics (which describes the universe on very small scales) is one of the most significant unsolved problems in physics. That problem isn’t likely to go away unless it turns out there’s some still-undiscovered angle to one or both of those theories.

“The question is, where does [general relativity] break down,” Reitze said, and will LIGO’s data on black holes provide the right laboratory for answering that question?

The detection of a gravitational-wave signal is significant for LIGO because it confirms that the experiment is “moving from novelty to real gravitational-wave science,” David Shoemaker, a spokesperson for the LIGO Scientific Collaboration and a professor of physics at MIT, said during the news conference. This gravitational-wave-hunting machine has officially demonstrated its ability to illuminate a once-dark sector of the universe.

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Astronomers Find Two Massive Black Holes On A Collision Course

June 6, 2017 by  
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Two monster black holes are apparently on a collision course near the heart of a nearby galaxy, a new study reports.

Astronomers have spotted an extremely bright object located about 1,500 light-years from the supermassive black hole known to occupy the heart of Cygnus A, an oft-studied galaxy that lies about 800 million light-years from Earth. 

“We think we’ve found a second supermassive black hole in this galaxy, indicating that it [the galaxy] has merged with another galaxy in the astronomically recent past,” study co-author Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in New Mexico, said in a statement.

“These two would be one of the closest pairs of supermassive black holes ever discovered, likely themselves to merge in the future,” Carilli added.

The researchers studied Cygnus A in 2015 and 2016 using the Very Large Array (VLA), a system of radio telescopes in New Mexico. These observations revealed the mysterious bright object, which had not appeared in earlier VLA images of Cygnus A from the 1980s and 1990s.

The completion of a VLA upgrade in 2012 motivated the new imaging campaign, study team members said. 

“To our surprise, we found a prominent new feature near the galaxy’s nucleus that did not appear in any previous published images. This new feature is bright enough that we definitely would have seen it in the earlier images if nothing had changed,” co-author Rick Perley, also of the NRAO, said in the same statement. “That means it must have turned on sometime between 1996 and now.”

Additional observations made in 2016 by the radio telescopes of the Very Long Baseline Array, which is also located in New Mexico, detected the object as well. 

Infrared images captured by NASA’s Hubble Space Telescope and Hawaii’s Keck Observatory between 1994 and 2002 show a faint object in the same spot within Cygnus A. This mysterious body had originally been interpreted as a clump of stars, but the recent and dramatic brightening is forcing a rethink, study team members said.

There are only two viable possibilities that could explain the new observations, the researchers added: The object is either a supernova or a supermassive black hole in outburst mode.

The team favors the black-hole hypothesis, because no known type of supernova could stay so bright for so long, the researchers said. The second supermassive black hole probably became so active after stumbling onto a lot of material to gobble up — perhaps a star that strayed too close, or gas stirred up by the galaxy merger, the researchers said.

“Further observations will help us resolve some of these questions,” said study lead author Daniel Perley, of the Astrophysics Research Institute of Liverpool John Moores University in England (and Rick Perley’s son). “In addition, if this is a secondary black hole, we may be able to find others in similar galaxies.”

The new study has been accepted for publication in The Astrophysical Journal. 

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Did Astronomers Find A Renegade Supermassive Black Hole

June 1, 2017 by  
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Astronomers have spied the possible aftermath of a colossal black hole collision that happened in the center of a galaxy far, far away.

Usually, researchers find supermassive black holes that are stationary objects, anchored in the cores of their galactic hosts. So astronomers became excited when they spotted a “renegade” supermassive black hole speeding through space, as reported in a new study.

The black hole, which is 160 million times the mass of Earth’s sun, appears to be the result of a collision with another black hole in a galaxy 3.9 billion light-years away from Earth.

Theory suggests that when two galaxies merge, supermassive black holes in the two galaxies’ cores orbit one another and eventually collide. The black hole pair may merge to create an even more massive supermassive black hole. But sometimes, the pair can violently recoil, and one of the black holes may be kicked in the opposite direction at great speed.

Researchers spotted what seems to be a “renegade” supermassive black hole speeding away from the site of a galactic merger.

The energy behind this powerful recoil is referred to as gravitational waves. As two black holes approach one other, they generate a lot of these ripples in space-time, and if the conditions are right, there might be a preponderance of gravitational waves blasted out in one direction, ejecting one of the black holes.

While searching through thousands of Sloan Digital Sky Survey (SDSS) observations in hopes of finding these recoiling black holes, the new study’s researchers noticed a very bright X-ray source at the center of one galaxy. This is a telltale sign that a black hole is active and growing, the researchers said in a statement. 

Then, using the Hubble Space Telescope, they discovered that the emissions were coming from two distinct objects. Further observations by NASA’s Chandra X-ray Observatory and the Keck telescope in Hawaii revealed that one of the two black holes is not in the center of its galaxy and is traveling at a different speed than its surroundings.

These clues suggest the object is a recoiling black hole, and the host galaxy itself also carries evidence of the merger that could have instigated it, the researchers said. The galaxy is forming stars at a high rate, for example, which is a sign that interstellar gases have been compressed. Also, the outer regions of the galaxy show signs of a massive disturbance.

Although the data supports a bona fide recoiling black hole, the researchers said in the statement, further observations are needed to rule out other explanations.

The study was recently accepted to The Astrophysical Journal and is available online on arXiv.org.

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Astronomers Find X-Ray Tsunami Rolling Through Galaxy Cluster

May 11, 2017 by  
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A wave of hot gas twice as wide as the Milky Way galaxy roils the nearby Perseus galaxy cluster, a new study indicates.

The wave, which measures 200,000 light-years across, likely formed billions of years ago, after a neighboring cluster clipped Perseus, researchers said. You can watch the monster wave roll in this awesome NASA video.

“The wave we’ve identified is associated with the flyby of a smaller cluster, which shows that the merger activity that produced these giant structures is still ongoing,” lead author Stephen Walker, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.

Galaxy clusters are the largest gravitationally bound structures in the universe. For example, Perseus — which lies 240 million light-years away from Earth, in the constellation of the same name — spans a vast 11 million light-years.

Most of the observable matter within galaxy clusters is superheated gas that glows in X-ray wavelengths, study team members said. Observations by NASA’s Chandra X-ray Observatory and other instruments have revealed many interesting formations in Perseus’ glowing gas, including an odd, 200,000-light-year-long concave feature dubbed “the bay.”

The bay generates no emissions, so — unlike some other features in the massive gas field — its origins don’t trace back to activity of the supermassive black hole at the core of Perseus’ central galaxy, NGC 1275, study team members said. And the bay’s shape doesn’t match those predicted by computer models that simulate normal gas sloshing, the scientists added.

So, the researchers re-analyzed Chandra images of the bay, filtering them to highlight edges and other important details. Then, the scientists compared these enhanced observations to computer simulations of merging galaxy clusters performed by astrophysicist John ZuHone, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

“Galaxy cluster mergers represent the latest stage of structure formation in the cosmos,” said ZuHone, who’s not a member of the new study’s team. (His simulations are available to other researchers in an online catalog.)

“Hydrodynamic simulations of merging clusters allow us to produce features in the hot gas and tune physical parameters, such as the magnetic field,” ZuHone said in the same statement. “Then we can attempt to match the detailed characteristics of the structures we observe in X-rays.”

Such comparative work led the researchers to identify a likely birth scenario for the bay. Long ago, Perseus’ gas had settled into two separate components: an interior “cold” region with temperatures around 54 million degrees Fahrenheit (30 million degrees Celsius) and a surrounding area three times hotter, the idea goes.

Then, a smaller cluster about 1,000 times more massive than the Milky Way galaxy grazed Perseus, coming within 650,000 light-years or so of its core, researchers said. This near miss roiled Perseus’ gas significantly, generating a spiral that expanded outward from the “cold” interior region.

years after the cluster flyby, this spiral reached 500,000 light-years from Perseus’ center and began producing huge waves in the cluster’s outer reaches. These features are basically enormous versions of “Kelvin-Helmholtz waves,” which appear at the interface of two fluids that are moving at different velocities, the researchers said.

“We think the bay feature we see in Perseus is part of a Kelvin-Helmholtz wave, perhaps the largest one yet identified, that formed in much the same way as the simulation shows,” Walker said. “We have also identified similar features in two other galaxy clusters, Centaurus and Abell 1795.”

The new study will appear in the June 2017 issue of the journal Monthly Notices of the Royal Astronomical Society.

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Astronomers Find Supermassive Black Hole In Tiny Galaxy

April 25, 2017 by  
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An incredibly powerful supermassive black hole has been found at the center of a tiny galaxy that is merging with another larger galaxy, a new study shows.

NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) has imaged a system known as Was 49. The system consists of a large disk galaxy called Was 49a that is colliding with a smaller dwarf galaxy called Was 49b, located about 26,000 light-years from the larger galaxy’s center. 

Data from the NuSTAR mission, along with information from the Sloan Digital Sky Survey and the Discovery Channel Telescope in Arizona, show luminous, high-energy X-rays shooting out from 49b’s galactic core, suggesting it hosts an active supermassive black hole that comprises more than 2 percent of the galaxy’s entire mass, scientists say.

“This is a completely unique system and runs contrary to what we understand of galaxy mergers,” Nathan Secrest, lead author of the study and postdoctoral fellow at the U.S. Naval Research Laboratory in Washington, D.C., said in a statement from NASA. “We didn’t think that dwarf galaxies hosted supermassive black holes this big. This black hole could be hundreds of times more massive than what we would expect for a galaxy of this size, depending on how the galaxy evolved in relation to other galaxies.”

The powerful bursts of high-energy radiation emitted from dwarf galaxy 49b are fueled by the gas and dust being gobbled up by the black hole. Normally, however, it is the larger of two merging galaxies that hosts the active supermassive black hole, according to the NASA statement. 

“That is because, as galaxies approach each other, their gravitational interactions create a torque that funnels gas into the larger galaxy’s central black hole,” NASA officials said. “But in this case, the smaller galaxy hosts a more luminous AGN [active galactic nucleus] with a more active supermassive black hole, and the larger galaxy’s central black hole is relatively quiet.” 

The pink-colored emissions captured in the image represent the gas and dust surrounding the active supermassive black hole, while the large green cloud represents the starlight of Was 49a. Although scientists have yet to determine how the supermassive black hole of 49b grew to be so big, they expect that it will collide with the dormant black hole of 49a in several hundred million years to form one ginormous galactic beast, according to the NASA statement. 

“This study is important because it may give new insight into how supermassive black holes form and grow in such systems,” Secrest said in the statement. “By examining systems like this, we may find clues as to how our own galaxy’s supermassive black hole formed.”

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Astronomers Begin Campaign To Photograph A Black Hole

April 18, 2017 by  
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The campaign to capture the first-ever image of a black hole has begun.

From today (April 5) through April 14, astronomers will use a system of radio telescopes around the world to peer at the gigantic black hole at the center of the Milky Way, a behemoth called Sagittarius A* (Sgr A*) that’s 4 million times more massive than the sun.

The researchers hope to photograph Sgr A*’s event horizon — the “point of no return” beyond which nothing, not even light, can escape. (The interior of a black hole can never be imaged, because light cannot make it out.) [The Strangest Black Holes in the Universe]

“These are the observations that will help us to sort through all the wild theories about black holes — and there are many wild theories,” Gopal Narayanan, an astronomy research professor at the University of Massachusetts Amherst, said in a statement. “With data from this project, we will understand things about black holes that we have never understood before.” 

The project, known as the Event Horizon Telescope (EHT), links up observatories in Hawaii, Arizona, California, Mexico, Chile, Spain and Antarctica to create the equivalent of a radio instrument the size of the entire Earth. Such a powerful tool is necessary to view the event horizon of Sgr A*, which lies 26,000 light-years from our planet, EHT team members said.

“That’s like trying to image a grapefruit on the surface of the moon,” Narayanan said.

During the current campaign, EHT is also eyeing the supermassive black hole at the core of the galaxy M87, which lies 53.5 million light-years from Earth. This monster black hole’s mass is about 6 billion times that of the sun, so its event horizon is larger than that of Sgr A*, Narayanan said.

These observations should help astronomers determine the mass, spin and other characteristics of supermassive black holes with better precision, team members said. The researchers also aim to learn more about how material accretes into disks around black holes, and the mechanics of the plasma jets that blast from these light-gobbling giants.

EHT could also reveal more about the “information paradox” — a long-standing puzzle about whether information about the material gobbled up by black holes can be destroyed — and other deep cosmological mysteries, team members said.

“At the very heart of Einstein’s general theory of relativity, there is a notion that quantum mechanics and general relativity can be melded, that there is a grand, unified theory of fundamental concepts,” Narayanan said. “The place to study that is at the event horizon of a black hole.”

 

Though the current observing campaign will be over soon, it will take a while for astronomers to piece together the images. For starters, so much information will be collected by the participating telescopes around the world that it will be physically flown, rather than transmitted, to the central processing facility at the Massachusetts Institute of Technology’s Haystack Observatory.

Then, the data will have to be calibrated to account for different weather, atmospheric and other conditions at the various sites. The first results from the campaign will likely be published next year, EHT team members said.

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Astronomers Find Largest Failed Star Outside The Milky Way

April 11, 2017 by  
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An ancient brown dwarf is the most massive and purest such “failed star” ever discovered, a new study suggests.

Researchers studied an object called SDSS J0104+1535, which lies about 750 light-years from Earth in the Milky Way’s “halo,” a population of extremely old stars above the galaxy’s familiar spiral disk.

SDSS J0104+1535 is a brown dwarf — a bizarre, gaseous body larger than a planet but too small to sustain the nuclear fusion reactions that power stars. New observations by the European Southern Observatory’s Very Large Telescope in Chile provide new details about this object, which astronomers think is 10 billion years old.  

For example, study team members said, SDSS J0104+1535 is about 90 times more massive than Jupiter, making it the heaviest known brown dwarf. (For perspective: The sun is 1,050 times more massive than Jupiter. And Jupiter is 318 times more massive than Earth.)

In addition, just 0.01 percent of SDSS J0104+1535 consists of elements other than hydrogen and helium — meaning that the body is 250 times purer than the sun, and the purest brown dwarf ever observed

“Pure” in this sense refers to the stuff originally present just after the Big Bang that created the universe 13.82 billion years ago — mostly hydrogen and helium, along with small amounts of lithium. All the naturally occurring elements heavier than these three were created inside stars over the eons.

“We really didn’t expect to see brown dwarfs that are this pure,” study lead author ZengHua Zhang, of the Institute of Astrophysics in the Canary Islands, said in a statement. “Having found one, though, often suggests a much larger hitherto undiscovered population. I’d be very surprised if there aren’t many more similar objects out there waiting to be found.”

The new study has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society. You can read it for free at the online preprint site arXiv.org.

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Can Stars Form Inside A Black Hole Jets?

April 7, 2017 by  
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Infant stars have been discovered inside raging streams of material spewed into space by a monstrous black hole, according to a new study. 

The rather resilient star babies were found in jets of material ejected into space by a monster black hole at the center of a galaxy 600 million light-years away from Earth. As is the case in many other galaxies, the incredible force of the black hole’s gravity accelerates the gas and dust around it, before eventually funneling the material into two jets that flow in opposite directions away from the black hole.

Inside one of those cosmic “fire hoses,” researchers found a population of stars that is “less than a few tens of millions of years old,” and most of which are being swept along in the outflow at a rapid clip, according to a statement from the European Southern Observatory, home to the Very Large Telescope (VLT) that made the observations possible. The jets appear to provide a rich environment for the stars to form in; the scientists found the stars appear to be brighter and hotter than stars that form in “less extreme” areas of the galaxy, according to the statement. [The Strangest Black Holes in the Universe]

The jet where the star formation was detected is coming from the center of one of two galaxies currently merging together, collectively known as IRAS F23128-5919. To detect the baby stars, the research team used the MUSE and X-shooter instruments on the VLT. The researchers initially made an indirect detection of the stars inside the thickly obscured jets. Later, they were able to directly observe the baby stars. 

“Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening, as it’s a very difficult observation,” Roberto Maiolino, head of the team that made the discovery and a professor of experimental astrophysics at the University of Cambridge, said in the statement. “Our results are exciting because they show unambiguously that stars are being created inside these outflows.” 

Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.

star-producing region, it may ultimately subject the stars to a turbulent fate. 

“The stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether,” Helen Russell, a researcher at the Institute of Astronomy in Cambridge, said in the statement. But Russell said that stars forming closer to the galaxy’s center “might slow down and even start heading back inwards.”

If cosmic jets are ejecting stars into space across the universe that could help explain how the region between galaxies becomes enriched with “heavy” elements, the statement said. Stars fuse light elements, like hydrogen and helium, into heavier elements, including carbon, nitrogen, oxygen and many others. The explosion of very massive stars can produce even more heavy elements. Once the ejected stars die, they could spew these heavy elements into the intergalactic medium.

Stellar formation inside the flows is considerable — the new study finds that a star about 30 times the mass of the sun is formed in the flow about once per year. 

“This accounts for over a quarter of the total star formation in the entire merging galaxy system,” according to the statement.  

That’s a significant-enough contribution that the fate of these stars could help determine the shape of a massive galaxy, the statement said. Elliptical and spiral galaxies have different structures suggesting different formation processes, but both types are surrounded by a halo of stars. Studying stars formed inside black hole jets could help explain how those features form.

“If star formation is really occurring in most galactic outflows, as some theories predict, then this would provide a completely new scenario for our understanding of galaxy evolution,” Maiolino said in the statement.

The new study appears today (March 27) in the journal Nature. 

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Are Astronomers About To Peek Inside A Black Hole?

April 6, 2017 by  
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Ever since first mentioned by Jon Michell in a letter to the Royal Society in 1783, black holes have captured the imagination of scientists, writers, filmmakers and other artists. Perhaps part of the allure is that these enigmatic objects have never actually been “seen.” But this could now be about to change as an international team of astronomers is connecting a number of telescopes on Earth in the hope of making the first ever image of a black hole.

Black holes are regions of space inside which the pull of gravity is so strong that nothing – not even light – can escape. Their existence was predicted mathematically by Karl Schwarzchild in 1915, as a solution to equations posed in Albert Einstein’s theory of general relativity.

Astronomers have had circumstantial evidence for many decades that supermassive black holes – a million to a billion times more massive than our sun – lie at the hearts of massive galaxies. That’s because they can see the gravitational pull they have on stars orbiting around the galactic centre. When overfed with material from the surrounding galactic environment, they also eject detectable plumes or jets of plasma to speeds close to that of light. Last year, the LIGO experiment provided even more proof by famously detecting ripples in space-time caused by two medium-mass black holes that merged millions of years ago.

But while we now know that black holes exist, questions regarding their origin, evolution and influence in the universe remain at the forefront of modern astronomy.

Catching a tiny spot on the sky

On April 5-14 2017, the team behind the Event Horizon Telescope hopes to test the fundamental theories of black-hole physics by attempting to take the first ever image of a black hole’s event horizon (the point at which theory predicts nothing can escape). By connecting a global array of radio telescopes together to form the equivalent of a giant Earth-sized telescope – using a technique known as Very Long Baseline Interferometry and Earth-aperture synthesis – scientists will peer into the heart of our Milky Way galaxy where a black hole that is 4m times more massive than our sun – Sagittarius A* – lurks.

Astronomers know there is a disk of dust and gas orbiting around the black hole. The path the light from this material takes will be distorted in the gravitational field of the black hole. Its brightness and colour are also expected to be altered in predictable ways. The tell-tale signature astronomers hope to see with the Event Horizon Telescope is a bright crescent shape rather than a disk. And they may even see the shadow of the black hole’s event horizon against the backdrop of this brightly shining swirling material.

The array connects nine stations spanning the globe – some individual telescopes, others collections of telescopes – in Antarctica, Chile, Hawaii, Spain, Mexico and Arizona. The “virtual telescope” has been in development for many years and the technology has been tested. However, these tests initially revealed a limited sensitivity and an angular resolution that was insufficient to probe down to the scales needed to reach the black hole. But the addition of sensitive new arrays of telescopes – including the Atacama Large Millimeter Array in Chile and the South Pole Telescope – will give the network a much-needed boost in power. It’s rather like putting on spectacles and suddenly being able to see both headlights from an oncoming car rather than a single blur of light.

The black hole is a compact source on the sky – its view at optical wavelengths (light that we can see) is completely blocked by large quantities of dust and gas. However, telescopes with sufficient resolution and operating at longer, radio millimetre wavelengths can peer through this cosmic fog.

The resolution of any kind of telescope – the finest detail that can be discerned and measured – is usually quoted as a small angle corresponding to the ratio of an object’s size to its distance. The angular size of the moon as seen from the Earth is about half a degree, or 1800 arc seconds. For any telescope, the bigger its aperture, the smaller the detail that can be resolved.

The resolution of a single radio telescope (typically with an aperture of 100 metres) is roughly about 60 arc seconds. This is comparable to the resolution of the unaided human eye and about a sixtieth of the apparent diameter of the full moon. But by connecting many telescopes, the Event Horizon Telescope will be about to achieve a resolution of 15-20 microarcsecond (0,000015 arcseconds), corresponding to being able to spy a grape at the distance of the moon.

What’s at stake?

Although the practice of connecting many telescopes in this way is well known, particular challenges lie ahead for the Event Horizon Telescope. The data recorded at each station in the network will be shipped to a central processing facility where a supercomputer will carefully combine all the data. Different weather, atmospheric and telescope conditions at each site will require meticulous calibration of the data so that scientists can be sure any features they find in the final images are not artefacts.

If it works, imaging the material inside the black hole region with angular resolutions comparable to that of its event horizon will open a new era of black hole studies and solve a number of big questions: do event horizons even exist? Does Einstein’s theory work in this region of extreme strong gravity or do we need a new theory to describe gravity this close to a black hole? Also, how are black holes fed and how is material ejected?

It may even even be possible to image the black holes at the center of nearby galaxies, such as the giant elliptical galaxy that lies at the heart of our local cluster of galaxies.

Ultimately, the combination of mathematical theory and deep physical insight, global international scientific collaborations and remarkable, tenacious long-term advances in cutting edge experimental physics and engineering look set to make revealing the nature of spacetime a defining feature of early 21st century science.

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Astronomers Find Runaway Star Siblings

March 30, 2017 by  
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Researchers have spotted a long-lost relative of two runaway stars — the three likely parted ways in the Orion nebula as recently as the 1400s (from Earth’s perspective).

Two of the young stars were previously discovered speeding away from one another using radio and infrared observations, and observers had traced back to where they could have originated if they’d been from the same system initially. But something didn’t quite add up: the two seemed to not have as much combined energy as expected, suggesting that there might be at least one more star that was involved in the system’s breakup.

Now, astronomers think they’ve found the third — another runaway star that came from that same spot in the star-forming region 540 years ago, pinpointed in images from the Hubble Space Telescope.

“The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” the new work’s lead researcher, Kevin Luhman of Penn State University, said in a statement. “Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars.”

“They’re probably only a few hundred thousand years old,” Luhman added. “In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”

The three stars are all in a region full of young stars called the Kleinmann-Low nebula, which is embedded in the Orion nebula 1,300 light-years away. Each is moving at top speeds of almost 30 times the speed of most of the nebula’s stars, researchers said in the statement, and the nebula’s thick shroud of dust hides them from most observers (often only radio waves, and sometimes infrared radiation, that the stars produce can make it through the dust).

Luhmann found the star while hunting for free-floating planets on a research team at the Space Telescope Science Institute in Maryland. He was looking at near-infrared data from Hubble’s Wide Field Camera 3, and noticed that one glowing spot had changed position in between 1998 and 2015 as compared to nearby stars — suggesting it was moving at about 130,000 mph (210,000 kph), according to the statement. 

Working backward, he found that it could have originated in the same spot as the other two runaways. He projected that two members of the multiple-star system approached close enough to merge or form a close binary, unleashing the gravitational energy to fling all the stars outward. (The other two stars are moving away from the origin point at 60,000 mph, or 97,000 kph, and 22,000 mph, or 35,000 kph, respectively.)

According to simulations, such interactions should happen often in crowded clusters of young stars.

“But we haven’t observed many examples, especially in very young clusters,” Luhman said. “The Orion Nebula could be surrounded by additional fledgling stars that were ejected from it in the past and are now streaming away into space.”

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Monster Galaxy Cluster Sheds Light On Cosmic Microwave Background

March 28, 2017 by  
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One of the largest galaxy clusters ever seen shines bright in this image from the Hubble Space Telescope. Called RX J1347.5-1145, this cluster lies 5 billion light-years from Earth.

Hubble’s observations of this galaxy cluster helped astronomers at the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to probe the secrets of the cosmos by watching how it interacts with the cosmic microwave background (CMB) — weak radiation left over from the Big Bang, when the universe as we know it was born.

The entire cosmos bears witness to the disruptive events surrounding the Big Bang. Marks left behind by the rapid expansion of space-time can be found by studying the universe’s most ancient light, the CMB. These 14 billion-year-old photons, or particles of light, now permeate the cosmos and can be used to learn about the universe via a phenomenon known as the Sunyaev-Zel’dovich effect.

Microwave radiation is invisible to the human eye, but astronomers can detect it. The microwave photons that create the CMB travel through the universe to Earth. “On their journey to us, they can pass through galaxy clusters that contain high-energy electrons,” NASA officials said in a statement. Passing through areas containing high-energy electrons can give these ancient photons get a little energy boost.

“Detecting these boosted photons through our telescopes is challenging but important,” NASA officials said. “They can help astronomers to understand some of the fundamental properties of the universe, such as the location and distribution of dense galaxy clusters.”

After ALMA observed the CMB around the galaxy cluster RX J1347.5-1145 (shown in blue), astronomers combined that data with an image from the Cluster Lensing and Supernova survey with Hubble (CLASH) to make this picture. Combining the visible-light image from Hubble with the invisible microwave data from ALMA helps astronomers understand how the CMB interacts with the galaxies inside the colossal cluster.

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Can Black Holes Rapidly Change Their Temperature?

March 10, 2017 by  
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Supermassive black holes are thought to be embedded in the middle of most large galaxies, including the Milky Way. These monsters feed from a surrounding disk of gas, dust and other material, called an accretion disk. The gravitational pull of the black hole can heat up material in the accretion disk, causing it to radiate light.

Young and energetic black holes can gobble up only so much material, however, before the feeding process produces hot streams of gas from the accretion disk. These black-hole winds travel at about a quarter of the speed of light, and have the potential to disturb star formation in their wake

Using NuSTAR and the European Space Agency’s XMM-Newton telescope, scientists have for the first time observed winds from a nearby black hole interacting with radiation coming from the black hole’s edge, according to the authors of a study.

Harrison’s team wanted to learn about the temperatures of these winds, so they looked at X-rays coming from the black hole’s edge. As the X-rays pass through the winds, chemical elements present in the winds — such as iron and magnesium — absorb some wavelengths of light in the X-ray spectrum. The spectrum then displays holes, also called “absorption features,” revealing more about the wind’s composition.

“While observing this spectrum, the team noticed that the absorption features were disappearing and reappearing in the span of a few hours,” according to a statement from the California Institute of Technology (Caltech). “The team concluded that the X-rays were actually heating up the winds to very high temperatures — millions of degrees Fahrenheit — such that they became incapable of absorbing any more X-rays. The winds then cool off, and the absorption features return, starting the cycle over again.”

Being able to study the properties of these winds offers scientists an opportunity to learn more about how those winds impact the evolution of galaxies.

“We know that supermassive black holes affect the environment of their host galaxies, and powerful winds arising from near the black hole may be one means for them to do so,” Fiona Harrison, NuSTAR principal investigator and a physics and astronomy professor at Caltech, said in the statement. “The rapid variability, observed for the first time, is providing clues as to how these winds form, and how much energy they may carry out into the galaxy.”

The researchers are planning to conduct more observations to learn how the winds are formed, where their source of power is from and how long they last, among other features. The findings will be published tomorrow (March 2) in the journal Nature.

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