At the center of the Milky Way is a supermassive black hole, 4.3 million times bigger than the sun, known as Sagittarius A*. It was unclear until recently how much of Sagittarius Awas in the galaxy’s core. Astronomers measured four distant stars’ speeds around the black hole. The stars’ movement indicates that the galaxy’s central mass is almost entirely made of matter from Sagittarius, A*. This leaves little space for stars, interstellar gas and dust, or dark matter.
” The Gemini observatories continue providing new insights into our galaxy’s nature and the immense black hole at its centre,” stated Martin Still, Gemini program officer with the U.S. National Science Foundation. Gemini will continue to lead the way in the description of the universe. “
The team conducted research at Gemini North, Hawaii, as part of the international Gemini Observatory program, which is funded by the NSF. To map the stars’ movement, the survey used spectroscopy from Gemini Near Infrared Spectrograph and the SINFONI instrument on European Southern Observatory’s Very Large Telescope Interferometer. Using the data from their observations, the team inferred that Sagittarius Acontains 99.9% of the mass at the galactic center.
Astronomers will next need to discover what lies in the middle of the Milky Way. What is the area that Sagittarius hasn’t claimed? Astronomers will discover more when they measure fainter stars farther away with greater precision.