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A Powerful Shrouded Starburst
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A Powerful Shrouded Starburst

March 3, 2011
These images show how a brilliant burst of star formation (red glow, right image) is revealed in infrared observations from NASA's Spitzer Space Telescope. The collision of two spiral galaxies, has triggered this luminous starburst, the brightest ever seen taking place far away from the centers, or nuclei, of merging galaxies.

The merging galaxies, known collectively as II Zw 096, can be clearly seen in the image from NASA's Hubble Space Telescope (left). This image combines light spanning the far-ultraviolet through the near-infrared. The real action in this galactic train wreck is barely hinted at in the red speckles near the middle of it all.

The booming blast of star formation only jumps out when Spitzer's mid-infrared view, represented in red, is folded into the mix (right). This tiny region may be as small as 700 light-years across - just a tiny portion of the full 50,000 light-year extent of II Zw 096 - yet it blasts out 80 percent of the infrared light from this galactic tumult. The surrounding shroud of dust renders the stars here nearly invisible in other wavelengths of light.

Researchers were surprised to see such a brilliant infrared glow in an area so far offset from the center of the spiral galaxy. Starbursts are often found crammed into the very centers of merging galaxies, but this is the brightest starburst ever seen outside a galaxy's nucleus. Based on Spitzer data, researchers estimate the starburst is cranking out stars at the breakneck pace of around 100 solar masses, or masses of our Sun, per year.

The Hubble image (left) represents ultraviolet light at a wavelength of 0.15 microns as blue, visible light at 0.44 microns as cyan, and near infrared light at 0.9 microns as red.

In the combined image (right) Hubble's far-ultraviolet and visible light at wavelengths of 0.15 and 0.44 microns is shown as blue, and the near infrared light at 0.9 microns is cyan. Spitzer's infrared light at 4.5 microns is represented by orange, and the mid-infrared light at 8.0 and 24 microns is red.

Observations of II Zw 096 were taken as part of the Great Observatories All-Sky LIRG Survey (GOALS).