For years, astronomers had been looking forward to watching the supermassive black hole at the center of our Milky Way galaxy tear apart a passing cloud of hydrogen gas that was called G2 — so they were surprised to discover that it wasn't destroyed during its close approach. Now they think they know why: G2 may not be a cloud of gas at all, but a pair of stars that smashed together to form one giant star, surrounded by a fog of gas and dust.
"G2 survived and continues happily on its orbit; a gas cloud would not do that," UCLA astronomer Andrea Ghez said in a news release from the Keck Observatory. "G2 was completely unaffected by the black hole; no fireworks." More objects like it have been identified. "G2 is not alone. We're seeing a new class of stars near the black hole, and as a consequence of the black hole," Ghez said. The findings about G2 are based on Keck telescope observations and were published online Monday in the Astrophysical Journal.
— Alan Boyle
In addition to Ghez, the authors of "Detection of Galactic Center Source G2 at 3.8 Micron During Periapse Passage" include G. Witzel, M.R. Morris, B.N. Sitarski, A. Boehle, S. Naoz, R. Campbell, E.E. Becklin, G. Canalizo, S. Chappell, T. Do, J.R. Lu, K. Matthews, L. Meyer, A. Stockton, P. Wizinowich, and S. Yelda.