Black hole or no black hole?

Abstract

Astronomers are among the most international of scientists. Yet chauvinism surfaces on a cosmic scale where the anxious search for a massive black hole at the centre of our Galaxy is concerned. The prodigious amounts of energy emitted from tiny regions at the centres of some nearby galaxies imply that they contain accreting black holes of masses ranging from 10^5 to 10^8 times the mass of our Sun (M⊙).The orbits of stars in the unspectacular centre of our nearest sister galaxy (Messier 31, visible to the naked eye in Andromeda) indicate that it contains at least 10^7 M⊙ in a form so dark' and concentrated as to suggest the presence of a black hole of about 10^6M⊙. Surely, some astronomers argue, nature cannot have been so unkind as to deprive our own magnificent Milky Way of such an ornament? On page 45 of this issue, Yusef-Zadeh, Morris and Ekers report the latest result of the scrutiny of the centre of the Milky Way.

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