Repaired Hubble Sees Strong Evidence of a Supermassive Black Hole in M87

Researchers using the refurbished Hubble Space Telescope to study the galaxy M87 have seen new and compelling dynamical evidence that a supermassive black hole lurks at the galaxy’s core. Using the Wide Field‐Planetary Camera, the astronomers obtained an image of what seems to be a gaseous accretion disk centered on the point of origin of a relativistic jet that emanates from M87. (See the figure at right.) Spectrographic measurements reveal that relative to M87’s overall motion, one side of the disk is receding from us at about 500 km/sec and the other is approaching at a similar velocity, strongly suggesting that the gas is orbiting the center of M87 at that velocity. (See the figure on page 18.) Given the 60‐light‐year distance of the two points from the center of the motion and assuming stable circular orbits, one readily deduces with ordinary Newtonian mechanics that material amounting to about ${\text{2.4×10}}^9$ solar masses ${\mathrm{(M}}_{\odot })$ lurks at the center of M87, in a volume that contains far too few visible stars to account for so much matter.