Arp 87: Merging Galaxies
from Hubble
From NASA’s Astronomy Picture of the Day
This dance is to the
death. Along the way, as these two large galaxies duel, a cosmic bridge of stars,
gas, and dust currently stretches over 75,000 light-years and
joins them.
The bridge itself is
strong evidence that these two immense star systems have passed close to each
other and experienced violent tides induced by mutual gravity.
As further evidence, the
face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many
young blue star clusters produced in a burst of star formation.
The twisted edge-on
spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and
surrounded by a curious polar
ring.
While such interactions
are drawn out over billions of years, repeated close passages should
ultimately result in the death of one galaxy in the sense that only one galaxy
will eventually result.
Although this scenario does
look peculiar, galactic mergers are thought to be common, with Arp 87
representing a stage in this inevitable
process.
The Arp 87 pair are about
300 million light-years distant toward the constellation Leo. The prominent
edge-on spiral at the far left appears to be a more distant background galaxy
and not involved in the on-going merger.
