BUBBLES AND JETS: An artist's conception of the Milky Way shows
the recently discovered Fermi bubbles, as well as the dual
gamma-ray jets for which evidence has just emerged. Image: David
A. Aguilar (CfA) At the center of our galaxy is a sleeping
giant, a black hole more than four million times as massive as
the sun. The Milky Way’s supermassive black hole is mostly
quiet, nibbling on small objects at the galactic center and
giving off only faint belches of radiation as it digests its
prey. But in the past the sleeping giant may have been wide
awake—and wreaking havoc. Astrophysicists at the
Harvard–Smithsonian Center for Astrophysics have uncovered
evidence of two ghostly but enormous beams of gamma rays, each
extending some 30,000 light-years from the galactic center, that
seem to mark a violent episode of black hole consumption
relatively recently in cosmic history. Supermassive black holes
in some other galaxies are much more active than Sagittarius A*
(Sgr A*), the lurker at the center of the Milky Way.