Number 109 (Story #3), January 8, 1993 by Phillip F. Schewe and Ben Stein|
A SOURCE OF INFRARED RADIATION HAS BEEN DISCOVERED NEAR THE GALACTIC CENTER at the location of the object called Sgr A*. The new IR results reinforce the idea, established by previous measurements of Sgr A* at radio, x-ray, and gamma wavelengths, that a black hole resides at the core of the Milky Way. At the AAS meeting, Laird Close of the University of Arizona (602-621-6523) presented pictures of the galactic core at wavelengths of 1.6 and 2.2 microns made using the 2.3-m telescope at Kitt Peak. The observations, employing adaptive-optics techniques in the infrared for the first time, had sufficient resolution to show that the IR source was no larger than 0.006 light years across. Arizona astronomer Joseph Haller presented separate IR studies of the velocities of stars as a function of distance out from Sgr A* showing that the velocities increased from nearly zero at a distance of 1.4 light years from Sgr A* to a velocity of nearly 100 km/sec at a distance of 0.7 light years. This pattern, plus the determination that there must be at least 100 times more mass inside the 0.7-light-year distance than can be accounted for by the observable stars alone, suggests to Haller that there should be a 900,000-solar-mass black hole at Sgr A*.