It is an object whose escape velocity equals or exceeds the speed of light. It is so small and
massive that even light could not escape, thus, it would be black.
1. One way to find black holes is to observe matter moving or orbiting at muchhigher speeds than
expected. By carefully mapping the motion, and then applying Kepler’s third law of orbital motion, it
is possible to measure the mass of an object even without seeing the object itself.
2. The deep gravitational field of a black hole can also produce a tremendous amount of light nearby and
around itself, even if the hole itself is dark. The infalling matter gets hot from the frictional drag too,
sometimes reaching temperatures of millions of degrees. That hot material glows brightly and emits far
more X-ray radiation and radio waves than would normally be expected from such a small volume of
space. By searching for these emissions, astronomers can deduce the presence of black holes even
though they cannot see the holes themselves.
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