Free Astronomy Magazine May-June 2018

18 MAY-JUNE 2018 SPACE CHRONICLES S0-2 as a spectroscopic binary,” said lead author Devin Chu of Hilo, an astronomy graduate student with UCLA’s Galactic Center Group. “It’s incredibly rewarding. This study gives us confidence that a S0-2 bi- nary system will not significantly af- fect our ability to measure gravi- tational redshift.” Einstein’s Theory of General Relativity predicts that light coming from a strong gravita- tional field gets stretched out, or “redshifted.” Researchers expect to directly measure this phenomenon beginning in the spring as S0-2 makes its closest approach to the supermassive black hole at the cen- ter of our Milky Way galaxy. This will allow the Galactic Center Group to witness the star being pulled at maximum gravitational strength – a point where any devia- tion to Einstein’s theory is expected to be the greatest. “It will be the first measurement of its kind,” said co-au- thor Tuan Do, deputy director of the Ga- lactic Center Group. “Gravity is the least well-tested of the forces of nature. Einstein’s theory has passed all other tests with flying colors so far, so if there are deviations meas- ured, it would cer- tainly raise lots of questions about the nature of gravity!” “We have been wait- ing 16 years for this,” said Chu. Astronomers discover S0-2 star is single and ready for Einstein test by Keck Observatory A stronomers have the “all- clear” for an exciting test of Einstein’s Theory of General Relativity, thanks to a new discov- ery about S0-2’s star status. Up until now, it was thought that S0-2 may be a binary, a system where two stars circle around each other. Hav- ing such a partner would have com- plicated the upcoming gravity test. But in a study published recently in The Astrophysical Journal , a team of as- tronomers led by a UCLA scientist from Hawaii has found that S0-2 does not have a significant other after all, or at least one that is massive enough to get in the way of critical measurements that as- tronomers need to test Einstein’s theory. The researchers made their discovery by ob- taining spectroscopic measurements of S0-2 using W. M. Keck Obser- vatory’s OH-Suppressing Infrared Imaging Spec- trograph (OSIRIS) and Laser Guide Star Adap- tive Optics. “This is the first study to investigate T he UCLA Galactic Center Group takes a photo together during a visit to Keck Observatory, located atop Maunakea, Hawaii. Members of the group will return to the Observatory this spring to begin observa- tions of S0-2 as the star travels towards its closest distance to the Galac- tic Center’s supermassive black hole. [UCLA Galactic Center Group]