Astronomers identify mysterious object at heart of Milky Way

A mysterious astronomical object known simply as G2 has intrigued and confounded researchers ever since it was found to be on a near-collision course with the supermassive black hole at the center of our galaxy. When it failed to produce the predicted celestial fireworks over the past few months, astronomers were left scratching their heads. Now, one team thinks it has figured out why nothing happened: G2 is not a gas cloud but a strange, more stable object formed from a pair of recently merged stars.

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> used the twin 10-meter Keck telescopes in Hawaii to observe G2 between March and August—spanning its expected closest approach and the months that followed. Viewing at the infrared wavelength of 3 micrometers, which can penetrate the fog around Sgr A*, the team found that G2 “continues to survive in orbit—it has not changed,” Ghez says. A gas cloud alone could not have survived a pass so close to the black hole, she says; she concludes that G2 must have a star at its heart, surrounded by a shell of dust. “It’s an unusual star, large, calculated from its brightness,” she says. The star is twice the mass of our sun but 100 times its size, the team reports this week in The Astrophysical Journal Letters.

Glad they decided to study it during the close approach. I’d thought it was a cloud of gas, glad to know I was wrong.