By Ron Cowen
By tracking the speed of stars close to the center of our galaxy, astronomers over the past 5 years have established that a black hole with a mass equal to 2.6 million suns lurks at the Milky Way’s core (SN: 1/24/98, p. 59). Now, researchers have measured for the first time the acceleration of three stars near the core. By determining how much the orbits of these stars’ are bent by the tug of the black hole, the scientists have more precisely calculated the beast’s location and mass.
To measure acceleration, Andrea M. Ghez and her colleagues, all of the University of California, Los Angeles, used the Keck I telescope atop Hawaii’s Mauna Kea to take a series of infrared images of the Milky Way’s nucleus. The scientists periodically observed the stars from 1995 to 1999 and report their results in the Sept. 21 Nature.