Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

January 14, 1997

Black Holes in Galactic Centres
Credit: D. Richstone (U. Mich) et al., HST, NASA

Explanation: Do all galaxies have black holes at their centres? Although not even a single galaxy has yet been proven to have a central black hole, the list of candidates has increased yet again. Recent results by astronomers using the Hubble Space Telescope now indicate that most - and possibly even all - large galaxies may harbour one of these dense beasts. In all the galaxies studied, star speeds continue to increase closer the very centre. This in itself indicates a centre millions of times more massive than our Sun is needed to contain the stars. This mass when combined with the limiting size make the case for the central black holes. Will we ever know for sure?

Tomorrow's picture: Black Hole Signature From Advective Disks

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