October 4, 2012

Today, UCLA astronomers using the W. M. Keck Observatory reported the discovery of a remarkable star that orbits the enormous black hole at the center of our Milky Way galaxy in a blistering 11-and-a-half years, the shortest known orbit of any star near this black hole.

The star, known as S0-102, may help astronomers discover whether Albert Einstein was right in his fundamental prediction of how black holes warp space and time, said Andrea Ghez, leader of the discovery team and professor of physics and astronomy, who holds UCLA’s Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics, and is a co-author. The research is published Oct. 5 in the journal Science.

Before this discovery, astronomers knew of only one star near the black hole with a very short orbit: S0-2, which Ghez used to call her “favorite star” and whose orbit is 16 years. (The “S” is for Sagittarius, the constellation containing the galactic center; its name is Latin for the archer.)

“I’m extremely pleased to find two stars that orbit our galaxy’s supermassive black hole in much less than a human lifetime,” said Ghez, who studies 3,000 stars that orbit the black hole, and has been studying S0-2 since 1995. Most of the stars have orbits of 60 years or longer, she said.

“It is the tango of S0-102 and S0-2 that will reveal the true geometry of space and time near a black hole for the first time,” Ghez said. “This measurement cannot be done with one star alone.”

Taft Armandroff, Director of the W. M. Keck Observatory, noted that “The pivotal research by Ghez’s UCLA group using the Keck Observatory has evolved from proving that a supermassive black hole exists in the center of our Galaxy, to testing the very fundamentals of physics. This is truly an exciting time in astronomy.”