NRAO: National Radio Astronomy Observatory

About this Image

The "Taffy" galaxies: This composite image shows the results of a collision between two galaxies, UGC 813 (right) and UGC 816 (left). The optical emission from stars appears in its natural color, 21 cm radio emission from interstellar atomic Hydrogen (HI) gas is shown in blue, and 1.4 GHz radio continuum emission in red. UGC 813 and UGC 816 were normal disk galaxies before they collided face-on at a speed of one million miles per hour about 50 million years ago. The disks of stars and dense clouds of molecular gas passed through each other relatively unharmed and are now separating. Diffuse HI gas clouds cannot interpenetrate and were stopped between the galaxies or thrown out in long tails by tidal forces. Disk magnetic fields are anchored by dense molecular clouds and are being stretched like bands of taffy between the galaxies as they separate. The bridge of magnetic fields and relativistic electrons stripped from the disks by the collision produces the radio continuum emission depicted in red. The wreckage from this "cosmic crash test" contains forensic evidence about both the collision itself and the nature of normal galaxies, through their response to such a collision. Investigator(s): J. J. Condon (NRAO), G. Helou (IPAC) and T. H. Jarrett (IPAC) Image Composition: J. M. Uson

Investigator(s):  J. J. Condon (NRAO), G. Helou (IPAC), T. H. Jarrett (IPAC)

Alternate Resolutions

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If you would like to obtain a higher resolution version of this image, please contact Pat Smiley.

For More Information

• Read the Journal article
• Read the NRAO Newsletter article
• Up one level for more info on Peculiar galaxies
• For unfamiliar terms, visit the NRAO Radio Astronomy Glossary

Technical Data

Telescope	VLA
Date of Observation	2001-07-27
Type of Observation	Spectral Line Observations
Center of Image	RA: 01:16:16.54, Dec: 46:44:24.20 (J2000)
Field of View	0.1667 x 0.1667 degrees



Astronomical database entries for UGC813
• Query NED for images of UGC813
• Query SIMBAD for more UGC813 data

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