No, you can’t see a black hole. What you might be able to see, though, is the way in which relativity predicts a spinning black hole will bend space, time, and light around it. Scientists say in a new study in Nature Physics that they are closer than ever to being able to see this effect in faraway black holes from our vantage point here on Earth.
Galaxies probably have spinning, supermassive black holes at their center, and spinning black holes possess two types of angular momentum, study coauthor Bo Thide explains. There’s spin angular momentum, which is analogous to what the Earth creates as it spins on its axis, and there’s orbital angular momentum, which is analogous to what the Earth creates as it orbits the sun. Thidé says that the second effect—orbital angular momentum—distorts light in a way that scientists who know what to look for might be able to see it from here.
“Around a spinning black hole, space and time behave in such an odd way; space becomes time, time becomes space, and the whole space-time is actually dragged around the black hole, becomes twisted around the black hole,” Professor Thidé explained. “If you have radiation source… it will then sense this twisting of spacetime itself. The light ray may think that ‘I’m propagating in a straight line’, but if you look at it from the outside, you see it’s propagating along a spiral line. That’s relativity for you.” [BBC News]
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One of these things is not like the other: Astronomers have spotted a dwarf galaxy that spans just 3,000 light years across (as opposed to our Milky Way’s diameter of 100,000 light years), but hosts an outsize supermassive black hole for its puny size.
From DISCOVER blogger Phil Plait:
Some smaller galaxies have supermassive black holes as well, but in general these dwarf galaxies have some structure to them, with a well-defined core. Henize 2-10, as you can see, it a mess! It doesn’t have much overall structure, which is why it’s classified as an irregular galaxy. The thinking for big galaxies is that the black hole forms at the same time as the galaxy itself, and to regulate the growth of each other. When you look at lots of big galaxies, there’s a pretty clear overall correlation between the mass of the black hole and the galaxy around it.
So it’s pretty weird that Henize 2-10 has a supermassive black hole at all, but it turns out the hole is also about a million times the mass of the Sun — that’s pretty freakin’ big for such a tiny galaxy! That’s 1/4 the mass of our own black hole, in a galaxy that itself is far smaller than ours.
For more details about this weird galaxy, check out the rest of this post at Bad Astronomy. And for more galaxy-black hole weirdness, read last week’s 80beats post about whether mergers of galaxies truly cause supermassive black holes to become hyperactive.
Related Content:
80beats: Study: Hyperactive Black Holes Aren’t Caused by Galactic Smash-ups
80beats: LHC’s Lack of Black Holes Rules Out Some Versions of String Theory
80beats: Far-Off Quasar Could Be the Spark That Ignites a Galaxy
80beats: Researchers Spot an Ancient Starburst from the Universe’s Dark Ages
Image: Reines, et al., NRAO/AUI/NSF, NASA
At the heart of most galaxies lies a supermassive black hole. And in some galaxies, the black hole is bigger and badder than usual. These raging overachievers, called active galactic nuclei, can be some of the brightest objects in space, sweeping up a huge amount of material from their local areas and emitting enough energy to outshine the galaxies around them. The question is, where do they get all the stuff to swallow? Not where scientists had expected, according to a new study.
An obvious answer—and the one that for years has seemed likeliest—is that these hyperactive black holes arise from the merger of galaxies. All the gas that comes together during a two-galaxy crash could feed a supermassive black hole, turning it from docile to brilliant. But there’s a problem.
“It’s totally intuitive,” said astrophysicist Knud Jahnke of the Max-Planck Institute for Astrophysics in Germany, a coauthor of the new study. “But it was a gut-feeling idea. In court you would say there was some circumstantial evidence for it, but no proof.” Earlier studies looked only at galaxies with the brightest active nuclei, which could have biased their results, Jahnke said. They also didn’t compare active galaxies to those with quiet black holes. [Wired]
For a study coming out in the Astrophysical Journal, Jahnke and others tried to put the galaxy merger hypotheses through a true controlled test, and they found no solid evidence to back it up.
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You know those black holes the Large Hadron Collider was going to make and kill us all? Well, not only are we still here, but the LHC doesn’t seem to be making black holes at all—their decay signature is markedly absent from the data collected so far.
While that is good for those of us who want to keep living (we jest—the hypothetical micro black holes posed no danger), it’s also helping physicists make up their minds about how many dimensions there are in our universe. The lack of black holes at the LHC nullifies some of the wackier versions of string theory which depend on multiple dimensions.
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Those two purple lobes in the figure-eight shape are balloons of gamma ray energy that reach out 25,000 light years above and below the plane of the galaxy. Yet these huge structures have remained hidden from astronomers, until now.
Using NASA’s Fermi Gamma-Ray Space Telescope, Doug Finkbeiner and colleagues detected the bubbles after they managed to remove from their images an obstructing “fog” of gamma rays between here and there.
Researchers do not yet know what produced the bubbles, but the fact that they appear to have relatively sharp edges suggests that they were produced in a single event. Finkbeiner said that would have required the rapid release of energy equivalent to about 100,000 supernovae, or exploding stars. One possibility is that there was a burst of star formation in the center of the galaxy producing massive, short-lived stars that exploded and ejected a great deal of gas and dust over a few million years. [Los Angeles Times]
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It’s one of Stephen Hawking‘s most famous hypotheses (though one often co-credited to other researchers): According to the rules of quantum mechanics, a black hole—from which nothing should be able to escape—actually can emit material in the form of Hawking radiation. In the thirty-plus years since the reknowned physicist made his prediction Hawking radiation has remained theoretical, but a research team now claims to have seen it right in the lab.
First, a quick refresher on Hawking radiation:
Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum. Hawking’s prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go. [Technology Review]
The lonesome, unpaired particles streaming away would make it appear that the black hole was emitting radiation, Hawking argued.
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If you want to make a supermassive black hole quickly, collide young, massive proto-galaxies. After running the numbers on a supercomputer, that’s what researchers have recently concluded. Their simulation shows that a collision between massive gas clouds could make a black hole “from scratch” in a relatively short time.
Supermassive black hole truly are super massive–possibly billions of times the mass of our sun. They also appear to be super old; some estimates say they formed less than a billion years after the Big Bang. Thus the puzzle, how do you get so big so quickly?
The paper which appeared online yesterday in Nature (with associated letter) modeled the collision of two gas clouds that formed into a unstable gas disk, which channeled gas into its center. Eventually this dense center collapsed in on itself to make the black hole king. (See simulations of the proto-galaxies colliding, above.)
“It has been perplexing how such black holes with masses billions of times the mass of the sun could exist so early in the history of the universe,” astronomer Julie Comerford of University of California Berkeley, who was not involved in the study, wrote in an e-mail to Wired.com. “These simulations are an important advance in understanding how those supermassive black holes were built up so quickly.” [Wired]
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I like the Milky Way. I dare say it’s my favorite galaxy, being home and all. But a blue star called HE 0437-5439 is in one big hurry to leave.
The star is zooming away from the Milky Way’s center at 16 million miles per hour, three times faster than our own sun glides across the galaxy. Astronomers had spotted the hasty traveler before—it’s one of 16 known “hypervelocity” stars. Now, with the help of the Hubble Space Telescope, Warren Brown of the Harvard-Smithsonian Center for Astrophysics traced the path of the star back to the event that allowed it to reach such great speed: a meeting with a black hole.
A hundred million years ago this star was one of three traveling together at a more sedate pace.
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Waltzing black holes, star-destroying black holes; it’s a black hole bonanza as the American Astronomical Society meets this week in Washington DC.
First, the orbiting pairs: Just about every galaxy has a supermassive black hole at its heart that is millions if not billions the size of our sun. Logic would suggest that when two galaxies merge, astronomers would see the two great black holes orbiting each other, but so far they’ve had tough luck, astronomer Julie Comerford says. “We expect the universe to be littered with these waltzing black holes,” Comerford said. “But until recently, only a few had ever been found.” Those missing black hole pairs posed problems for theories of how galaxies merge and grow [Wired.com].
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Which came first: A galaxy or the supermassive black hole at its center? Thanks to a misfit quasar, astronomers have some new clues.
Quasars are particular kinds of black holes that release incredibly intense jets of energy, and scientists spied this one five billion light-years away. To their surprise, the astronomers found that unlike most quasars, this one was ”naked” and not situated at the centre of a galaxy. However, there was a companion galaxy close to it creating new stars at a frantic rate equivalent to about 350 suns per year [The Telegraph].
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Talk about a long trip. An exploding star‘s burst of light traveled 13 billion years, from the early days of the universe to the present day, before being detected by astronomers here on Earth. Researchers say this exploding star is the most distant blast ever seen.
The light from the distant explosion, called a gamma-ray burst, first reached Earth on April 23 and was detected by NASA’s Swift satellite. Gamma-ray bursts are thought to be associated with the formation of star-sized black holes as massive stars collapse. Within hours, telescopes around the world were turned on the burst — the most violent explosions in the universe — observing its fading afterglow to glean clues about its source and location [SPACE.com].
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At the University of Cambridge it’s out with black holes, in with tiny vibrating strings of energy. The prestigious professorship that was most recently held by Stephen Hawking, the physicist whose great contributions to the field include new models of black holes, has been given to the string theory luminary Michael Green.
The Lucasian Professorship was established in 1663 and previous holders have included Isaac Newton [BBC News]; it’s considered one of the most prestigious academic posts in the world. Hawking held the job for 30 years, but stepped down in September following his 67th birthday, in accordance with a university rule.
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In a lab in Nanjing, China, two researchers are mucking about with what could be called the world’s first artificial black hole–but there’s no reason for alarm. The researchers, Qiang Cheng and Tie Jun Cui, haven’t created a doomsday device, but rather a nifty experiment that harnesses the strange properties of metamaterials. Physicists have already learned how to steer light around an object within a metamaterial to create an invisibility cloak…. Now Qiang and Tie have created a metamaterial that distorts space so severely that light entering it (in this case microwaves) cannot escape [Technology Review].
The lab experiment simulates a cosmological black hole, where the intense gravity curves space-time, sucking in any matter or radiation that gets too close. Not even light can escape a black hole (hence the name). The researchers couldn’t duplicate the intense gravity, but they could build a metamaterial with a physical structure that would make light curve into its central core, never to return. The device they built works only with microwaves so far, but the researchers say a visible light black hole is the next step.
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Physicists in Washington State and Louisiana recently spent two years hunting for the mysterious gravitational waves first predicted by Einstein, but detected nothing: zilch, zero, nada, nary a ripple. But that “null result” is itself of great value, researchers say, because it tells them where to look for the waves next. The findings are a nice reminder that scientific progress isn’t always about the dramatic discovery; it’s often a long, careful process of testing hypotheses, analyzing results, and heading back to the drawing board.
Einstein’s theory of general relativity states that every time mass accelerates — even when you rise up out of your chair — the curvature of space-time changes, and ripples are produced. However, the gravitational waves produced by one person are so small as to be negligible. The waves produced by large masses, though, such as the collision of two black holes or a large supernova explosion, could be large enough to be detected [SPACE.com].
Beyond those large disturbances, the universe is thought to be filled with small disturbances left over from the rapid period of expansion that followed the Big Bang, in a phenomenon known as the stochastic (meaning randomly distributed) gravitational wave background. If the expansion of the newborn universe had produced strong gravity waves, the physicists working at the two Laser Interferometer Gravitational-wave Observatory (LIGO) centers would have detected them. Since they found nothing, researchers have determined that smaller waves were produced, which they’ll need more sensitive instruments to detect. Says study coauthor Vuk Mandic: “We now know a bit more about parameters that describe the evolution of the universe when it was less than one minute old” [Sky & Telescope].
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Stephen Hawking, the world’s leading theoretical physicist, was among a group of 16 to receive the Presidential Medal of Freedom, the highest civilian award. The medal honors those who have significantly contributed to world peace, U.S. security or other endeavors.
Pres. Barack Obama presented the award, lauding Hawking’s immense contributions in spite of his physical disability due to a neurological disorder. “From his wheelchair, he has led us on a journey to the farthest and strangest reaches of the cosmos. In so doing, he has stirred our imagination and showed us the power of the human spirit,” [Sky News], Obama said of Hawking as he placed the medal around his neck. Besides his contributions to the field of physics through his research on topics like black holes and cosmology, Hawking, 67, is also the author of the best-selling science book A Brief History of Time.
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