A black hole is an object so dense that its gravitational field is so intense that nothing, even light, can escape its surface.
The size of a black hole, at least one that's not spinning around
(rotating), is given by:
|Object Name||Mass (kg)||Schwartzchild radius|
|Earth||5.9724 x 1024||0.890911 cm|
|Sun||1.9891 x 1030||2.953518 km|
|Deneb||1.2 x 1032||178.182183 km|
|Our galaxy||5 x 1041||4982.723247 AU|
|Virgo Cluster||1044||15.694944 light years|
|The Universe||1053||1.57 x 1010light years|
The mass of the universe is based on there being about 5 x 1011
galaxies (Based on the Hubble deep field count) and that each galaxy is about
half the mass of the our galaxy, the milky way.
The last number, 1.57 x 1010light years is quite interesting. It's well within the error bars for the current observed radius of the universe.
Our Universe is a black hole!!!
Why this is so is unknown. It might be just a coincidence, or it could have deep physical meaning. No one knows.
The background image used is of the open cluster M67. It comes from the Palomar sky survey I.