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Name: Carrie E Victor
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Question:
How can you detect a black hole, when light cannot escape it?



Replies:
Black holes have a very intense gravitational field. Therefore if we see very intense gravitational field, or some sign of it, then there can be a black hole there, of course we can never be 100% sure. We do see some stars like Cygnus X1, which seem to have a compact massive object in its neighbor- hood. This invisible companion is accreting mass that has been ejected by the visible star. The mass falling into this compact object is heating up to very high temperatures, something which can happen in intense gravita- tional fields. Mass of this invisible object is determined by observing the orbit of the visible star around it. Temperature of the infalling mass is measured by observing the X ray emission from the heated material.

Jasjeet S Balga


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