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The Question
(Submitted February 06, 2000)
Hi, I am interested in black holes and have taken a Astronomy 100
college class. My question is: if you were to take a picture of a
star-field and a black hole were to come between you and the center
of the same star-field, and it is relatively near to you, how would
the appearance of the star-field change? Thanks!
The Answer
The black hole would look black, since any stars behind it would be
shadowed by it. Around the black hole, outside its event horizon,
though, you would see a rim of light from stars behind it. Some of
the light from these stars that started out at an angle from you will
be bent by the strong gravitational field and would reach your eye.
In a very real sense, the black hole is a "gravitational lens."
For a pictorial explanation look at
http://www.mpifr-bonn.mpg.de/staff/hfalcke/bh/sld11.html
We hope this helps!
Enectali Figueroa and John Cannizzo
for "Ask a NASA Scientist"
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