|In most pictures galaxies seem to be rather organized and
substantial if not "solid-like" objects. However, no process better
shows the ethereal and delicate nature of galaxies than when they
collide. Unlike dancers on a dance floor, a galactic tango will
strip stars and gas in a mutual promenade. The space in between the galaxies
fills with these stars in new and perturbed orbits. The masses of the galaxies,
their intrinsic internal structures, and their relative velocities (timescales)
ultimately determine the resulting structure of the interaction.
In this example NGC 5216 (top) and NGC 5218 (below) have luminous debris connecting them across a distance that is no less than 22,000 lightyears. P. C. Keenan noted this double galaxy enigma in 1935 and noted the peculiar structure in his paper. It was later "rediscovered" by observers at Lick and Palomar observatories. Note that NGC 5218 has a countertide; a tidal tail that is in the opposite direction of the center of mass of the system. This is a typical structure of interacting double galaxy systems. These galaxies are estimated to be more than 100 million light years away.
|L R G B color production was used to create this image.||
Minimum credit line: Sid Leach and Wil Milan/Adam Block/NOAO/AURA/NSF
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