Black hole
hideIn general relativity, a black hole is a region of space in which the gravitational field is so powerful that nothing, including light, can escape its pull. The black hole has a one-way surface, called an event horizon, into which objects can fall, but out of which nothing can come. It is called "black" because it absorbs all the light that hits it, reflecting nothing, just like a perfect blackbody in thermodynamics. Quantum analysis of black holes shows them to possess a temperature and Hawking radiation.
Despite its invisible interior, a black hole can reveal its presence through interaction with other matter. A black hole can be inferred by tracking the movement of a group of stars that orbit a region in space which looks empty. Alternatively, one can see gas falling into a relatively small black hole, from a companion star. This gas spirals inward, heating up to very high temperature and emitting large amounts of radiation that can be detected from earthbound and earth-orbiting telescopes. Such observations have resulted in the scientific consensus that, barring a breakdown in our understanding of nature, black holes do exist in our universe.
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News tagged with black holes
Mysterious X-rays from a Nearby Galaxy
Nov 13, 2009 |
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(PhysOrg.com) -- The nucleus of an active galaxy, an AGN, contains a massive black hole that is vigorously accreting material. In the process it typically ejects jets of particles and radiates brightly at ...
NASA's Great Observatories Celebrate International Year of Astronomy
Nov 10, 2009 |
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(PhysOrg.com) -- A never-before-seen view of the turbulent heart of our Milky Way galaxy is being unveiled by NASA on Nov. 10. This event will commemorate the 400 years since Galileo first turned his telescope ...
Swift, XMM-Newton satellites tune into a middleweight black hole
Nov 10, 2009 |
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(PhysOrg.com) -- While astronomers have studied lightweight and heavyweight black holes for decades, the evidence for black holes with intermediate masses has been much harder to come by. Now, astronomers ...
Stars Fueled by Dark Matter Could Hold Secrets to the Universe
Nov 03, 2009 |
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(PhysOrg.com) -- The first stars in the universe may have been very different from the stars we see today, yet they may hold clues to understanding some of the mysterious features of the universe. These "dark ...
Fermi Telescope Detects Gamma-Ray From 'Star Factories' in Other Galaxies
Nov 02, 2009 |
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Nearby galaxies undergoing a furious pace of star formation also emit lots of gamma rays, say astronomers using NASA's Fermi Gamma-ray Space Telescope. Two so-called "starburst" galaxies, plus a satellite ...
New Celestial Map Gives Directions for GPS
Space & Earth / Space Exploration
Oct 29, 2009 |
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(PhysOrg.com) -- Many of us have been rescued from unfamiliar territory by directions from a Global Positioning System (GPS) navigator. GPS satellites send signals to a receiver in your GPS navigator, which ...
X-Ray Jets from Galaxies
Oct 19, 2009 |
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(PhysOrg.com) -- Some dramatic galaxies eject gigantic, collimated jets of ionized gas millions of light-years long, powered by the massive black holes at their centers. The ionized jets are detected at radio ...
Chinese scientists create metamaterial black hole
Oct 16, 2009 |
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(PhysOrg.com) -- Two physicists in China have used metamaterials to create the first artificial electromagnetic black hole. The scientists, Qiang Cheng and Tie Jun Cui from the Southeast University in Nanjing, ...
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Cosmic archaeology: Astrophysicists use new spectrographs to look far back into the history of the universe
Oct 13, 2009 |
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(PhysOrg.com) -- The distant past of the universe is moving closer. Astronomers are using special spectrographs to investigate galaxies in the depths of the universe as part of the Sloan Digital Sky Survey ...
Black Holes Go 'Mano a Mano'
Oct 06, 2009 |
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(PhysOrg.com) -- Two black holes in galaxy NGC 6240 are only 3,000 light years apart -- and getting closer.
Cosmic entropy could be 100 times greater than previously thought
Oct 06, 2009 |
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(PhysOrg.com) -- A new analysis of supermassive black holes has discovered the entropy of the universe is much greater than previously thought, which means it may also be very slightly closer to ultimate heat death.
Very High Energy Gamma Rays
Sep 25, 2009 |
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(PhysOrg.com) -- Gamma-rays are the most energetic known form of electromagnetic radiation, with each gamma ray being at least one hundred thousand times more energetic than an optical light photon. The most ...
New Vista of Milky Way Center Unveiled
Sep 22, 2009 |
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(PhysOrg.com) -- A dramatic new vista of the center of the Milky Way galaxy from NASA's Chandra X-ray Observatory exposes new levels of the complexity and intrigue in the Galactic center. The mosaic of ...
Invading black holes explain cosmic flashes
Sep 18, 2009 |
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(PhysOrg.com) -- Black holes are invading stars, providing a radical explanation to bright flashes in the universe that are one of the biggest mysteries in astronomy today.
Sophisticated telescope camera debuts with peek at nest of black holes
Sep 15, 2009 |
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Less than two months after they inaugurated the world's largest telescope, University of Florida astronomers have used one of the world's most advanced telescopic instruments to gather images of the heavens.
