Sunday, 4 November 2007
When worlds collide (and then some)
Extra credit from Hubble Information Centre / John Dubinski (UofToronto) / Science Daily.
The Hubble Space telescope has captured this picture of a pair of galaxies, known collectively as Arp 87 merging.
Arp 87 is in the constellation Leo, the Lion, approximately 300 million light-years away from Earth. These observations were taken in February 2007 with the Wide Field Planetary Camera 2. Light from isolated blue, green, red, and infrared ranges was combined to form this colour image.
The two main players comprising Arp 87 are NGC 3808 on the right (the larger of the two galaxies) and its companion NGC 3808A on the left. NGC 3808 is a nearly face-on spiral galaxy with a bright ring of star formation and several prominent dust arms. Stars, gas, and dust flow from NGC 3808, forming an enveloping arm around its companion. NGC 3808A is a spiral galaxy seen edge-on and is surrounded by a rotating ring that contains stars and interstellar gas clouds.
Although this is only one instance of the hundreds of interacting and merging galaxies known in our nearby Universe it’s no less magnificent for that.
Interacting galaxies often exhibit high rates of star formation. Many lines of evidence like colours of their starlight, intensity of emission lines from interstellar gas and far-infrared output from heated interstellar dust support this fact. Some merging galaxies have the highest levels of star formation we can find anywhere in the nearby Universe.
On a slightly more parochial level our own Milky Way galaxy is due to collide and merge with near neighbour Andromeda in about 3 Billion years time.
At the moment, Andromeda is about 2.2 million light years away from us but the gap is closing at 500,000 km/hour. Andromeda is the only big spiral galaxy moving towards the Milky Way and it is thought that the two galaxies are in fact a bound pair in orbit around one another.
Shame to miss the show really.