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Black Holes

Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself to the point of zero volume and infinite density, creating what is known as a singularity. As the density increases, the path of light rays emitted from the star are bent and eventually wrapped irrevocably around the star. Any emitted photons are trapped into an orbit by the intense gravitational field; they will never leave it. Because no light escapes after the star reaches this infinite density, it is called a black hole. But contrary to popular myth, a black hole is not a cosmic vacuum cleaner. If our Sun was suddenly replaced with a black hole of the same mass, the earth's orbit around the Sun would be unchanged.

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Is Our Universe at Home Within a Larger Universe? Last Updated on 2010-03-29 00:00:00 BLOOMINGTON, Ind. (April 5, 2010) – Could our universe be located within the interior of a wormhole which itself is part of a black hole that lies within a much larger universe? Such a scenario in which the universe is born from inside a wormhole (also called an Einstein-Rosen Bridge) is suggested in a paper from Indiana University theoretical physicist Nikodem Poplawski in Physics Letters B. The final version of the paper was available online March 29 and will be published in the journal edition April 12. FIGURE CAPTION –– Einstein-Rosen bridges like the one visualized above have never been observed in nature, but they provide theoretical physicists and cosmologists with solutions in general relativity by combining models of black holes and white holes. Poplawski takes advantage of the Euclidean-based coordinate system called isotropic coordinates to... More »
Black Hole Hunters Set New Distance Record Last Updated on 2010-01-28 16:15:42 GARCHING, GERMANY (Jan. 28, 2010) – Astronomers using ESO’s Very Large Telescope have detected, in another galaxy, a stellar-mass black hole much farther away than any other previously known. With a mass above fifteen times that of the Sun, this is also the second most massive stellar-mass black hole ever found. It is entwined with a star that will soon become a black hole itself. The stellar-mass black holes [1] found in the Milky Way weigh up to ten times the mass of the Sun and are certainly not be taken lightly, but, outside our own galaxy, they may just be minor-league players, since astronomers have found another black hole with a mass over fifteen times the mass of the Sun. This is one of only three such objects found so far. The newly announced black hole lies in a spiral galaxy called NGC 300, six million light-years from Earth. “This is the most distant... More »
Newborn Black Holes May Add Power to Many Exploding Stars Last Updated on 2010-01-27 00:00:00 WASHINGTON, DC (Jan. 27, 2010) – Astronomers studying two exploding stars, or supernovae, have found evidence the blasts received an extra boost from newborn black holes. The supernovae were found to emit jets of particles traveling at more than half the speed of light. Previously, the only catastrophic events known to produce such high-speed jets were gamma-ray bursts, the universe's most luminous explosions. Supernovae and the most common type of gamma-ray bursts occur when massive stars run out of nuclear fuel and collapse. A neutron star or black hole forms at the star's core, triggering a massive explosion that destroys the rest of the star. "The explosion dynamics in typical supernovae limit the speed of the expanding matter to about three percent the speed of light," explained Chryssa Kouveliotou, an astrophysicst at NASA's Marshall Space Flight Center in... More »
Suzaku Catches Retreat of a Black Hole's Disk Last Updated on 2009-12-10 00:00:00 GREENBELT,  MD (Dec. 8, 2009) – Studies of one of the galaxy's most active black-hole binaries reveal a dramatic change that will help scientists better understand how these systems expel fast-moving particle jets. FIGURE CAPTION – GX 339-4, illustrated here, is among the most dynamic binaries in the sky, with four major outbursts in the past seven years. In the system, an evolved star no more massive than the sun orbits a black hole estimated at 10 solar masses. Credit: ESO/L. Calçada Binary systems where a normal star is paired with a black hole often produce large swings in X-ray emission and blast jets of gas at speeds exceeding one-third that of light. What fuels this activity is gas pulled from the normal star, which spirals toward the black hole and piles up in a dense accretion disk. "When a lot of gas is flowing, the dense disk reaches nearly... More »
Fermi Telescope Peers Deep into Microquasar Last Updated on 2009-12-01 11:07:45 GREENBELT, MD (Dec. 1, 2009) – NASA's Fermi Gamma-ray Space Telescope has made the first unambiguous detection of high-energy gamma-rays from an enigmatic binary system known as Cygnus X-3. The system pairs a hot, massive star with a compact object -- either a neutron star or a black hole -- that blasts twin radio-emitting jets of matter into space at more than half the speed of light. FIGURE CAPTION – In Cygnus X-3, an accretion disk surrounding a black hole or neutron star orbits close to a hot, massive star. Gamma rays (purple, in this illustration) likely arise when fast-moving electrons above and below the disk collide with the star's ultraviolet light. Fermi sees more of this emission when the disk is on the far side of its orbit. Credit: NASA's Goddard Space Flight Center Astronomers call these systems microquasars. Their properties -- strong emission across a... More »