Archive for bar

The Curious Case of the Twisted Ring

Posted in The Universe and Stuff with tags , , , , , , , on July 21, 2011 by telescoper

Just time for a quickie this morning, prompted by the appearance of our own Professor Matt Griffin on the Today programme on BBC Radio 4 earlier on talking about newly published results from the Herschel Space Observatory. I didn’t hear it live as I’m strictly a Radio 3 person, but it must have made a pleasant change from stories about the imminent collapse of the euro and continuing extraordinay revelations about widespread corruption involving the British media, police force and political establishment. Among all this doom and gloom it’s nice to hear news of something that’s actually successful.

Anyway, the news from Herschel is that it has unveiled a ring structure in the centre of our Milky Way galaxy. The ribbon of gas and dust is more than 600 light years across and appears to be twisted, for reasons which have yet to be explained. The origin of the ring could yield important clues about the history of the Milky Way.

Warmer gas and dust from the Centre of our Galaxy is shown in blue in the  image below, while the colder material appears red. The ring, in yellow, is made of gas and dust at a temperature of just 15 degrees above absolute zero. The bright regions are denser, and include some of the most massive and active sites of star formation in our Galaxy.

and here it is with the curious ring drawn on with crayons:

The central region of our Galaxy is dominated by an elongated structure, rather like a bar, which stirs up the material in the outer galaxy as it rotates over millions of years and is probably connected with the spiral structure seen in the disk of the Milky Way. The ring seen by Herschel lies right in the middle of this bar, encircling the region which harbours a super-massive black hole at the centre of our galaxy. The ring of gas is twisted, so we see two loops which appear to meet in the middle. These are seen in yellow in the image above, tilted slightly such that they run from top-left to bottom-right. Secondly, it seems to be slightly offset from the very centre of our Galaxy. The reason for the ring’s twist and offset are unknown, but understanding their origin may help explain the origin of the ring itself. Computer simulations indicate that bars and rings such as those we see in the centre of our Galaxy can be formed by gravitational interactions, either within the Milky Way itself or between it and the nearby Andromeda galaxy, M31.

For the experts, and others interested, the scientific paper containing these results can be found here.