I've been posting a lot of nice astronomical images lately, but sometimes one comes along and blows me completely away. How fantastically gorgeous is this?
Holy Haleakala! [Click to galactinate.]
That spiral galaxy is NGC 6872, and as you can see in this image from the Gemini South telescope it's getting its clock cleaned by the littler spiral -- IC 4970 -- just to the right. The two are undergoing a galactic collision, a colossal event playing out over hundreds of millions of years. NGC 6872 is currently the victim here; its spiral arms are clearly distorted and being flung wide by the gravitational interaction. However, the smaller IC 4970 will be the ultimate loser in this battle: it will fall into the bigger galaxy, be torn apart, and eventually consumed in its entirety, becoming a part of NGC 6872. Bigger galaxies do this to smaller ones all the time; the Milky Way is in the process of eating several small galaxies even as you read this (I have details in articles linked below; see Related Posts).
This pair has been observed by other telescopes, including the composite picture here of images by the Spitzer Space Telescope (which sees in the infrared), The Very Large Telescope (visible light), and Chandra (X-rays), which I rotated to match the Gemini shot and rescaled a bit. Interestingly, in the Chandra image the smaller galaxy has a bright point source core blasting out X-rays, indicating it's an active galaxy, meaning the supermassive black hole there is actively gobbling down matter. That's not obvious in the Gemini image because dust in the galaxy's core hides the energy, but X-rays can get through it. Astronomers think there's not enough material in IC 4970 to feed the hole, so it must be stripping off cold gas from the bigger galaxy. You can see a hint of that in both images here.
Another cool thing about this image is that the target galaxies were actually suggested by high school students for a contest! The Australian Gemini Office organizes the contest every year, which is to find scientifically important and aesthetically pleasing astronomical targets for the monster telescope. In 2010 the Sydney Girls High School Astronomy Club won (pictured). My pal Travis Rector then organized the observations and put together this incredible image.
And the new contest for 2011 is already underway. If you know some high school students who'd like the chance to point an 8 meter telescope, then send them to the contest website! Imagine having that on your college application.
Image credits: Sydney Girls High School Astronomy Club, Travis Rector (University of Alaska, Anchorage), Ángel López-Sánchez (Australian Astronomical Observatory/Macquarie University), and the Australian Gemini Office; NASA/CXC/SAO/M.Machacek, ESO/VLT, NASA/JPL/Caltech
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