MPE: Gas Cloud in Galactic Center Is Part of Gas Streamer

[bystander]

Gas Cloud in Galactic Center Is Part of Larger Gas Streamer
Max Planck Institute for Extraterrestrial Physics (MPE) | 2014 Nov 24

[i]April 2014: High-resolution image of the gas cloud G2 at the centre of our Milky Way with the SINFONI instrument at the VLT. The red part of the cloud approaches the 4 million solar masses black hole (indicated with a cross) at velocities of a few thousand km/s. The blue part has already passed the closest distance to the black hole and moves away again. The initially spherical could has been stretched by the strong gravitational field of the black hole by a factor 50 in the direction of motion. The cloud's size from red to blue now corresponds to 900 times the Earth-Sun distance. The solid line shows the orbit of the gas cloud. The dashed lines show the orbit of the star with the best known orbit (S2). The positions of the neighbouring stars are indicated as well. [b](Credit: MPE)[/b][/i]

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In November, astronomers at the Max Planck Institute for Extraterrestrial Physics presented new observations of the gas cloud G2 in the galactic centre originally discovered in 2011. These data are in remarkably good agreement with an on-going tidal disruption. As a complete surprise came the discovery that the orbit of G2 matches that of another gas cloud detected a decade ago, suggesting that G2 might actually be part of a much more extensive gas streamer. This would also match some of the proposed scenarios that try to explain the presence of G2. One such model is that G2 is originating from the wind from a massive star.

The gas cloud G2 was originally detected by Stefan Gillessen and his colleagues at the Max Planck Institute for Extraterrestrial Physics (MPE) in 2011. It is on a highly eccentric orbit around the galactic centre and observations in 2013 have shown that part of the gas cloud is already past its closest approach to the black hole, at a distance of roughly 20 light hours (a bit more than 20 billion kilometres or 2000 Schwarzschild radii). The new, deep infrared observations with the SINFONI instrument at the VLT track the ongoing tidal disruption of the gas cloud by the powerful gravitational field. While the shape and path of the gas cloud agrees well with predictions from the models, so far there has been no significant enhanced high-energy emission, as one might have expected from the associated shock front.

But a closer look into the data set led to a surprise. “Already a decade ago, another gas cloud – which we now call G1 – has been observed in the central region of our galaxy,” remarks Stefan Gillessen. “We explored the connection between G1 and G2 and find an astonishing similarity in both orbits.” ...

The Galactic Center Cloud G2 and Its Gas Streamer - Oliver Pfuhl et al

• arXiv.org > astro-ph > arXiv:1407.4354 > 16 Jul 2014 (v1), 05 Nov 2014 (v2)

[MargaritaMc]

But http://asterisk.apod.com/viewtopic.php?f=31&t=34063 where we read

The mystery about a thin, bizarre object in the center of the Milky Way headed toward our galaxy’s enormous black hole has been solved by UCLA astronomers using the W. M. Keck Observatory, home of the two largest telescopes on Earth. The scientists studied the object, known as G2
... While some scientists believed the object was a cloud of hydrogen gas that would be torn apart in a fiery show, Ghez and her team proved it was much more interesting.

“G2 survived and continues happily on its orbit; a gas cloud would not do that,” said Andrea Ghez, UCLA professor of physics and astronomy. ... Instead, the team has demonstrated it is a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust, and choreographed by the black hole’s powerful gravitational field.

When I looked through the References in the paper by Pfuhl et al which is the subject of this MPE news release, the Astrophysical Letters paper by Dr Ghez's group (Gunther Witzel et al., published in the arXiv in October.) was not listed.

I'm puzzled.

[BDanielMayfield]

I'm puzzled.

This part of our galaxy is the most puzzling area, and not just to us amateurs Margarita. There's a great deal of dust, foreground stars, etc. that has to be looked though or past over the 30,000 lys between us and the Milky's Ways core.

Astronomers will no doubt be trying to solve this puzzle for a long time to come.

Bruce

[MargaritaMc]

I'm puzzled.

This part of our galaxy is the most puzzling area, and not just to us amateurs Margarita. There's a great deal of dust, foreground stars, etc. that has to be looked though or past over the 30,000 lys between us and the Milky's Ways core.

Astronomers will no doubt be trying to solve this puzzle for a long time to come.

Bruce

I was more puzzled by why this paper by Pfuhl et al didn't make reference to the work by Ghez and her team at the UCLA Galactic Center Group which is well known publicly as well as academically.
For example, this Universe Today article of November 4 this year

M