New images from NASA’s Chandra X-Ray Observatory show the environment around the supermassive black hole at the heart of M87, a nearby giant elliptical galaxy. Chandra detected loops and rings in the hot gas that surrounds the galaxy. These loops are evidence of periodic eruptions near the supermassive black hole, which send shockwaves through the surrounding gas. These outbursts happen every few million years, and prevent the gas in the cluster from cooling to create stars.
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Finding All the Black Holes
Black holes might be invisible, but the superheated matter piling up around them shines brightly in the gamma ray spectrum. Most of these black holes are so far away, their gamma rays look like a diffuse background radiation that covers the sky. ESA’s Integral spacecraft recently calibrated the level of this background radiation by watching a point of sky, and let the Earth pass in front of it, to slowly block it out. Using these calculations, astronomers will be better able to distinguish point sources of gamma rays from the wash of background radiation.
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Fine Tuning the Search for Black Holes
Although black holes can’t be seen directly, they’re relatively easy to find. Matter spiraling into a black hole becomes superheated, shines brightly, and is visible across the Universe. A new supercomputer simulation has fine tuned the energy calculations for atoms in the vicinity of a black hole. This is very important, because astronomers working on black holes will base their assumptions on these atomic data. The new calculations bring the potential error rates down to a few percent, enhancing the accuracy of other research.
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Supermassive Black Holes Prevent Star Formation
The supermassive black holes thought to be lurking at the heart of most galaxies could create such a hostile environment around them that they prevent the formation of new stars. This is according to new research assisted by NASA’s Galaxy Evolution Explorer (GALEX). The space-based telescope observed more than 800 galaxies, and found that the larger galaxies had fewer young stars. Astronomers believe that jets blasting out of supermassive black holes could clear out gas and dust; potential star forming material.
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The Search for Hidden Black Holes
Look into the sky with X-ray instruments, and you’ll see a background radiation in all directions. Astronomers think these X-rays are produced by the supermassive black holes at the centres of most galaxies. But astronomers can’t find these black holes, which should be bright in the most energetic range of the electromagnetic spectrum. Maybe they’re hiding; shrouded in thick clouds of gas and dust. Or maybe something else is generating all the X-ray background radiation.
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A New View of Quasars
Some of the brightest objects in the Universe are quasars. A mystery for decades, most astronomers now believe quasars are the bright centres of galaxies with actively feeding supermassive black holes. A team of researchers have found evidence that there might be something very different at the heart of these galaxies to cause quasars. Instead of black holes consuming matter, there could be objects with powerful magnetic fields that act like propellers, churning matter back into the galaxy.
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Magnetic Fields Help Black Holes Pull In Matter
Even though the gravity from black holes is so strong that light can’t even escape, we can see the radiation from the superheated matter that’s about to be consumed. Until now, scientists haven’t been able to explain how all this matter continuously falls into the black hole – it should just orbit, like planets going around a star. New data from the Chandra X-Ray Observatory shows that a black hole’s powerful magnetic field creates a turbulence in surrounding matter that helps drive it inward to be consumed.
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Everything’s on the Menu for Supermassive Black Holes
The supermassive black holes that lurk at the heart of most galaxies have enormous appetites. They’ve already consumed millions of times the mass of our own Sun, and they’re not done yet. Everything’s on the menu: mostly gas, dust, planets and stars, but the occasional exotic delicacy gets consumed too. “Compact objects”, such as stellar mass black holes, neutron stars, and white dwarfs occasionally fall into their grasp too. But these objects don’t go with a whimper; they make screams we’ll soon hear across intergalactic space.
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Podcast: Dark Energy Stars
Black holes… you know. Cosmic singularities that can contain the mass of billions of stars like our Sun. Where the pull of gravity is so strong, nothing, not even light can escape their fearsome grasp. They’re the source of much discussion, indirect observation and science fiction speculation. But according to George Chapline from Lawrence Livermore National Laboratory in California, they don’t exist. Instead we have dark energy stars, which are connected to that mysterious force accelerating the expansion of the Universe.
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The Sky is Full of Black Holes
X-ray image of the Chandra Deep Field-North. Image credit: NASA/PSU Click to enlarge
Data from X-ray observatory surveys show that black holes are much more numerous and evolved differently than researchers would have expected, according to a Penn State astronomer.
“We wanted a census of all the black holes and we wanted to know what they are like,” said Niel Brandt, professor of astronomy and astrophysics. “We also wanted to measure how black holes have grown over the history of the Universe.”
Brandt and other researchers have done just that by looking at a patch of sky in the Northern hemisphere called the Chandra Deep Field-North, using NASA’s Chandra X-ray Observatory and a similar patch in the Southern hemisphere called the Extended Chandra Deep Field-South. Surveys also are being carried out in other parts of the sky using both Chandra and the European Space Agency’s X-ray Multi-Mirror Mission-Newton.
The researchers looked at X-ray emissions because areas around black holes emit X-rays as well as visible light. The penetrating nature of X-rays provides a direct way to identify the black holes. Using X-rays also enables astronomers to pinpoint the black holes at the centers of galaxies without their signal being washed out by the visible light coming from a galaxy’s stars, Brandt told attendees at the annual meeting of the American Association for the Advancement of Science in St. Louis, Mo. Feb. 17. The black holes they studied were those that reside at the centers of galaxies and are actively emitting X-rays, therefore they are called active galactic nuclei.
“We find active super massive black holes at the centers of massive galaxies,” said Brandt. “Our galaxy also has its own black hole at its center measuring 2.6 million solar masses. Our black hole is not active today, but we presume it was active in the past.”
These deep, extragalactic X-ray surveys looked at carefully chosen patches of sky, that are largely free of anything that might interfere with obtaining the X-ray data. Chandra looked at the Chandra Deep Field-North — an area of sky two thirds the size of the full Moon — for the time span of 23 days over a two-year period. The researchers detected about 600 X-ray sources. After comparing the X-ray images with optical images of exactly the same slice of sky taken by the Hubble Space Telescope, nearly all 600 point sources corresponded to optical galaxies, suggesting that the black holes that were sources for the X-ray signature were in the centers of galaxies.
“X-ray astronomers are doing better than anyone else by about a factor of ten, in identifying these active galactic nuclei” said Brandt. “With more time we could do even better, going even deeper.”
What the researchers found was that super massive black holes are more numerous than we might have expected. They also found that black holes evolved differently than astronomers expected prior to the Chandra work. Extrapolating from the 600 black holes found by Chandra, Brandt suggests that there are about 300 million super massive black holes in the whole sky.
The existence of so many black holes, confirmed that what was once thought to be a truly diffuse cosmic X-ray background radiation, actually comes from point sources.
In the 1960s, astronomers discovered quasars, very distant, highly luminous black holes, in galactic centers. Quasars, initially called quasi-stellar radio sources, were studied intensely. Researchers soon realized that only some of these objects were radio emitters and that they formed early in the history of the Universe.
“While quasars are spectacular, they are not representative of typical active galactic nuclei,” said Brandt. “Now, using Chandra and other X-ray observatories, we can find and study the moderate-luminosity, typical active galactic nuclei in the distant, high-redshift Universe.”
Quasars and moderate-luminosity active galactic nuclei also evolved differently. Quasars are a phenomenon of young galaxies, while moderate-luminosity, active galactic nuclei peaked later in cosmic time.
“We would like to know if active galactic nuclei change over cosmic time,” said Brandt. “Do black holes feed and grow in the same way over the history of the Universe?”
Researchers looked at the relative amount of power coming out in X-rays compared to other wavelengths and found that this ratio does not change over 13 billion years of time. They looked at the X-ray spectra and found that these also did not change through time.
“Despite the enormous changes in the space density of back holes, the individual engines powering active galactic nuclei are remarkably stable,” Brandt said.
Brandt believes that Chandra could observe the Chandra Deep Field-North for a longer period of time and obtain more sensitive, deeper data. This would bring to light galaxies that are currently obscured. It would also gather more X-rays allowing better X-ray spectral and variability analyses. With more sensitive probing, the researchers are also detecting an increasing number of non-active galaxies like our own.
“Chandra has worked well for six years now,” said Brandt. “There is no reason why Chandra and Newton cannot continue to observe for another 10 or more years.”
Original Source: PSU News Release