Word: sun
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Dates: during 1970-1979
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Incredible as it may seem, scientists are now postulating supergiant black holes as well, monsters with event horizons millions of miles across and formed from a mass equal to that of billions of suns. Observations with the big telescopes at California's Palomar and Arizona's Kitt Peak National observatories strongly support the likelihood that at least one such heavyweight exists in M87, a galaxy that appears to be spewing out a great jet of matter. Astronomers found that M87's center is ten times as bright as the rest of the galaxy, and is surrounded by stars orbiting...
...theory, a German colleague named Karl Schwarzschild considered one of general relativity's consequences. If a star were to become sufficiently compact and dense, Schwarzschild found, its gravity would so warp space and time around it that the star would literally enclose itself. For a celestial body of the sun's mass, the critical radius turned out to be about 3 km (2 miles). If the star shrunk beyond that, it would vanish. This so-called Schwarzschild radius, or event horizon, is in effect the black hole's boundary. Any matter crossing it simply disappears...
...between two powerful competing forces. On the one hand, there is the great outward pressure on the star's gases created by radiation and heat from its internal fires. On the other, there is the inward pull of the star's gravity. In a star like the sun, the battle between radiation and gravity is long stalemated; the sun has been shining for some 5 billion years and will remain relatively unchanged for another 5 billion. After the star exhausts most of the hydrogen near its core and begins to burn hydrogen in its outer regions, it swells into...
Preoccupying himself with this problem while traveling by ship from India to England to take up studies at Cambridge in the early 1930s, the young Chandrasekhar came to an astonishing conclusion. His calculations showed that if a star is larger than 1.4 times the mass of the sun when it begins its collapse, it will compress to a state even more dense than that of a white dwarf. How far could the star collapse? In one of the great understatements of modern science, Chandrasekhar would only say: "One is left speculating on other possibilities...
...because gravity is so weak at long range, detecting its waves, says Harvard's Smarr, is "like measuring fluctuations in the dis tance between the earth and sun equal to the diameter of a human hair." So far no one has been able to accomplish that feat. But investigators in the U.S. and abroad are hoping to succeed with a new generation of extremely sensitive gravity detectors that rely on lasers, devices using superchilled metals and other advanced gadgetry...