Galaxy dance of death creates starburst shockwave

Joanna Carver, reporter

(Image: Gemini Observatory/AURA)

Meet a poor crazy mixed-up galaxy, NGC 660. It's a lenticular galaxy, meaning it's not a crowd-pleasing spiral or a shapeless blob elliptical, but essentially both. Visible in this image from a Gemini telescope on the mountain Mauna Kea, Hawaii, is a surrounding ring of gas, dust and stars, which is what's confusing astronomers.

First, some bad news: in a few billion years, the Andromeda galaxy (which, on a clear night you might be able to see from your backyard without a telescope) is going to swallow the Milky Way. That's us. It's nothing personal, it's just what galaxies do sometimes. Anyway, this won't happen until long after apes have taken over the Earth.

At first, that seemed the easiest explanation for how NGC 660 formed.

However, when that happens, we usually see a collapsed core at the galaxy's centre and sudden heightened activity of star formation, not to mention an extra supermassive black hole at the centre of the new galaxy. Also missing are the tails of ejected stars, gas and dust that get thrown out of the newly merged galaxies as a result of the violence of the event.

Brian Svoboda of the University of Arizona believes the ring came from a "tidal accretion event scenario" - in simplest terms, the gravitational dance of death of a pair of galaxies resulted in a massive shockwave.

The shockwave created gigantic blue stars, in this case 100 times the mass of our sun. They exploded, adding to the chaos, creating more and more shockwaves and turning NGC 660 into a starburst galaxy, one of the most intense star-forming environments.

"It really is the most incredibly picture I've seen of the galaxy," Svoboda said. "None of the other images I've seen, including those from the Hubble Space Telescope, show the star-forming region with such clarity."

To top it off, NGC 660's host galaxy and ring rotate at velocities inconsistent with the amount of gas they contain. This points straight at the existence of huge amounts of dark matter, that invisible, elusive substance that is thought to make up the huge majority of the universe. This weird, wonderful galaxy further may offer some clues, if it feels like talking.

Source: http://feeds.newscientist.com/c/749/f/10897/s/24aab388/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A120C10A0Cgalaxy0Edance0Eof0Edeath0Ecreates0Bhtml0Dcmpid0FRSS0QNSNS0Q20A120EGLOBAL0Qonline0Enews/story01.htm

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