Gas Cloud is More of a Streamer in the Galactic Center

Astronomers are getting a closer look at the gas cloud G2 in a galactic center that was originally discovered in 2011. The new observations reveal a bit more about this gas cloud, and show that it might be part of a much more extensive gas streamer.

The gas cloud was originally detected in 2011. It's on a highly eccentric orbit around the galactic center, and part of the black hole is actually already past its closest approach to the black hole-at a distance of roughly 20 light hours.

"Already a decade ago, another gas cloud-which we now call G1-has been observed in the central region of our galaxy," said Stefan Gillessen, one of the researchers, in a news release. "We explored the connection between G1 and G2 and find an astonishing similarity in both orbits."

What's interesting is that G1 had already passed the pericenter in 2001. The similarity of the orbits suggested that G1 was about 13 years ahead of G2.

"Our basic idea is that G1 and G2 might be clumps of the same gas streamer," said Oliver Pfuhl, lead author of the new study. "In this case, we should be able to simultaneously fit both data sets and, indeed, our model captures the G1 and G2 orbits remarkably well."

The findings reveal that G2 is actually part of a streamer of gas in addition to G1. It's possible that both G1 and G2 are clumps in the wind of one of the massive disk stars, which could have been ejected about 100 years ago close to the apocenter of the G2 orbit. It's also possible that they could be part of a large star enveloped by an extended gas cloud.

The findings are published in The Astrophysical Journal.