2 items found
Photographer is exactly "Image composition: J. M. Uson"
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Creator:Legacy Astronomical Images
Series:Galaxies Series
Unit:Peculiar Unit
Type:Legacy Astronomical Image
Description: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. [show more]
Creator:Legacy Astronomical Images
Series:Galaxies Series
Unit:Spiral Unit
Type:Legacy Astronomical Image
Description:This image of the spiral galaxy M51, also known as the "Whirlpool Galaxy," and its companion NGC5195 combines observations of neutral Hydrogen emission obtained with the Very Large Array with optical images (R, B) from the Second Palomar Observatory Sky Survey - STScI Digital Sky Survey. The optical data show the emission of stars in these galaxies as well as the dust; the latter can be seen as dust lanes in the spiral arms of M51 itself and in obscuring the eastern (left hand) part of its companion, NGC5195. They also show foreground stars in our own Milky Way galaxy as well as some background galaxies. The spectral-line observations of neutral atomic hydrogen (depicted by bluish hues) yield the distribution, as well as the kinematics, of the neutral Hydrogen gas. The long tidal tail of neutral Hydrogen was shaken loose by the dance of these two galaxies.
The 21cm spectral-line observations were obtained with the VLA in B, C and D configurations and reduced separately by the observers to produce high-resolution (B, 8 arcsecond) and a low resolution (C+D, 15 arcsecond) images. These images were combined with some smoothing done to the edges of the higher resolution structures to merge them into the low-resolution image. This image was made for illustration purposes only and should not be used for quantitative research. The original HI images can be obtained from the observers or remade from the data in the VLA archive.
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