|Object||Actual Diameter (kilometers)||Scale Diameter (centimeters)|
|Blue supergiant HDE 226868||30,000,000||300|
|Accretion disk in Cygnus X-1||20,000,000||200|
|Bulge in accretion disk||700,000||7|
|X-Ray emitting region||20,000||0.2|
|Black hole event horizon||60||0.0006|
On a larger scale in which the black hole is the size of a penny, the Sun would be the size of your schoolyard, and the blue supergiant HDE 226868 would be the size of a city.
MYTH: A black
hole in space would devour everything in our galaxy.
TRUTH: There is so much space between the stars that a black hole would not affect any objects except those very close to it.
MYTH: The black
hole in the Cygnus X-1 system is devouring the blue supergiant.
TRUTH: Less than a thousandth of the mass of the blue supergiant will fall into the black hole before it too dies, a million or so years from now.
MYTH: Matter which
falls into a black hole reappears somewhere else in the universe.
TRUTH: The matter remains in the black hole; in fact, it is the matter in a black hole which causes the gravitational force which allows us to discover these objects.
MYTH: The gravity
of a black hole is different from the gravity of a normal object.
TRUTH: If the Sun were to suddenly turn into a black hole (which it won't, by the way, because its gravity is too weak for it to completely collapse in on itself, the Earth and planets would continue to move in the normal way. However, the Earth would have lost its source of heat and light!
MYTH: Black holes
are very dense.
TRUTH: Small and medium black holes are very dense, but a supermassive black hole with a 100 million solar masses, for example would have a density the same as water. [You can work this out from the mass of the black hole and the radius of its event horizon; this assumes that all of the matter is distributed within the entire event horizon, not just in the singularity.]
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