The two W.
M. Keck Telescopes on Mauna Kea, Hawaii, observing the galactic center. The
lasers are used to create an artificial star in the Earth’s upper atmosphere, which is then used to measure the blurring effects
of the lower atmosphere (the effect that makes the stars twinkle in the night sky). The
blurring gets corrected in real time with the help of a deformable mirror. This
is the adaptive optics technique. Credit: Ethan Tweedie
UCLA astronomers report 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 research co-author Andrea Ghez, leader of the discovery team and a UCLA professor of physics and astronomy who holds the Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics.
The research is published Oct. 5 in the journal Science.
Before this discovery, astronomers knew of only one star with a very short orbit near the black hole: 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 and the black hole).
"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.
" Black holes, which form out of the collapse of matter, have such high density that nothing can escape their gravitational pull, not even light. They cannot be seen directly, but their influence on nearby stars is visible and provides a signature, said Ghez, a 2008 MacArthur Fellow.
Einstein's theory of general relativity predicts that mass distorts space and time and therefore not only slows down the flow of time but also stretches or shrinks distances.
"Today, Einstein is in every iPhone, because the GPS system would not work without his theory," said Leo Meyer, a researcher in Ghez's team and lead author of the study. "What we want to find out is, would your phone also work so close to a black hole? The newly discovered star puts us in a position to answer that question in the future."
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