Twisted ring of gas orbits galactic center

Jun 01, 2011 By Steve Nerlich, Universe Today
A Herschel PACS (Photodetector Array Camera and Spectrometer) image of a dark line of cool gas which is thought to be an elliptical ring surrounding the galactic center. The galaxy’s central supermassive black hole Sagittarius A (Sgr A) is labelled. The differential velocity of clouds in the ring may result from interaction with Sgr A. Credit: ESA/Herschel/NASA/Molinari et al.

The Herschel Space Observatory scanned the center of the galaxy in far-infrared and found a cool (in all senses of the word) twisting ring of rapidly orbiting gas clouds. The ring is estimated to have dimensions of 100 parsecs by 60 parsecs (or 326 by 196 light years) – with a composite mass of 30 million solar masses.

The ring is proposed to oscillate twice about the galactic mid-plane for each orbit it makes of the galactic center – giving it the apparent shape of an infinite symbol when viewed from the side.

The research team speculate that the ring may be conforming to the shape of a standing wave – perhaps caused by the spin of the central galactic bulge and the lateral movement of gas across the galaxy’s large central bar. The researchers suggest that the combination of these forces may produce some kind of gravitational ‘sloshing’ effect, which would account for the unusual movement of the ring.

The estimated shape of the 100 by 60 parsec ring. Note the oscillating shape from a lateral perspective - and from above, note the ring encircles the supermassive black hole Sagittarius A*, but the black hole is not at its center. Credit: Molinari et al.

Although the ring is estimated to have an average orbital velocity of 10 to 20 kilometers a second, an area of dense cloud coming in close to the galaxy’s central supermassive black hole, Sagittarius A*, was clocked at 50 kilometers a second – perhaps due to its close proximity to Sagittarius A*.

However, the researchers also estimate that Sagittarius A* is well off-centre of the gas ring. Thus, the movement of the ring is dominated by the dynamics of the galactic bulge – rather than Sagittarius A, which would only exert a significant gravitational influence within a few parsecs of itself.

Explore further: 'Eye of Sauron': Using supermassive black holes to measure cosmic distances

More information: Molinari et al A 100 parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the galactic center.

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User comments : 3

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omatumr
Jun 02, 2011
This comment has been removed by a moderator.
LKD
1 / 5 (1) Jun 02, 2011
For me, the orbit and the association of Sg B2 and Sg C seems to not fit the simplified ellipse. Hopefully the pdf will help explain it better.

I do question this statement: "Thus, the movement of the ring is dominated by the dynamics of the galactic bulge rather than Sagittarius A, which would only exert a significant gravitational influence within a few parsecs of itself."

Um. The entire galaxy revolves around a barycenter of Sgr A. When isn't it significant?
Shootist
3 / 5 (2) Jun 08, 2011
As I understand it, there are no point masses. The galaxy orbits the gravitational field created by everything in the Shapely Center.
Callippo
1 / 5 (1) Jul 22, 2011
In my theory the flat shape of galaxy emerged from streams of particles, emanated from central black hole jets and falling toward galactic plane like giant double fountain. Now these jets are mostly down, because the excessive matter evaporated from central black hole, nevertheless there are still strong stream of neutrinos, which are gushing from poles of central collapsar and they're affecting the symmetry of the central area of galaxy.

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