Researchers are closing in on ironclad evidence for the black
hole believed to lurk at the center of our Milky Way galaxy.
Astronomers used a "virtual" telescope spanning more than 2,800
miles (4,500 km) to home in on Sagittarius A* ("A-star"), the
light source believed to mark the location of a black hole four
million times as massive as the sun. They were able to resolve
Sagittarius A* to within 37 microarcseconds, the width of a
baseball on the moon as seen from Earth. Based on the size of
the light-emitting region, they believe it is offset from the
exact location of the black hole, which pulls gas and dust into
a disk swirling around it that gives off light. Instead, they
speculate that Sagittarius A* is either high-speed gas on one
side of the rotating accretion disk or a jet of matter being
ejected from around the black hole. The case for a black hole
was already "pretty solid," says study author Shepherd Doeleman,
an astrophysicist at the Massachusetts Institute of Technology's
Haystack Observatory. "