Colliding Galaxies Erupt with Violent Beauty

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Things get violent when galaxies collide, and nature puts on one spectacular show. As our own Ray Villard explains, these gorgeous color pictures are chock full of information about our galactic and extragalactic neighbors.

So what exactly is going on in this picture of the Antennae galaxies?

The Antennae are so named due to their bug-like shape in wide-field optical images. Not quite spiral or elliptical, irregularly-shaped galaxies such as these were once thought to be rare oddities. We now know that messy, interacting galaxies once ruled the universe and that such processes were instrumental in building the cosmos we see around us today.

In the top picture, infrared light from the Spitzer Space Telescope is

shown in red, visible light data from the Hubble Space Telescope in

yellow, and x-ray light from the Chandra X-Ray Observatory in blue.

Each of these highlights a different process in the merging system.

See, more bug-like?

Though I first said that galaxy collisions are violent, no stars actually collide in the process. They are so small on galactic scales and spread so far apart that they simply change their gravitational dance around their galaxies. Surely, some get slowly flung away in long tidal arms as seen in the wide-field image, but that is hardly apocalyptic.

The gas within galaxies, however, does collide, and an avalanche of star formation commences. Newborn stars heat up surrounding dust clouds, causing them to glow in the infrared, thus being detected by Spitzer. Massive stars born in the merger explode in violent supernovae, leaving behind gas that glows with x-rays to be picked up by Chandra. The galaxies’ older stellar tenants still shine on in visible light to be detected by Hubble, completing the galactic picture.

All of these pictures were taken several years apart and recently combined. However, the merger has been ongoing for 100 million years, so not much changes in such a short time span. Indeed, the violence of stellar birth and death in these dancing galaxies seems frozen in time for us to see in all its splendor.

Image Credits: Top – NASA, ESA, SAO, CXC, JPL-Caltech, STScI, J. DePasquale (Harvard-Smithsonian CfA), and B. Whitmore (STScI); Bottom – Ground-based image by Robert Gendler