NGC 922: Collisional
Ring Galaxy
From NASA’s Astronomy Picture of the Day
From NASA’s Astronomy Picture of the Day
Why does this galaxy have
so many big black holes? No one is sure.
What is sure is
that NGC 922 is a ring galaxy created by the collision of a large and
small galaxy about 300 million years ago.
Like a rock thrown into a pond, the ancient collision sent ripples of high density gas out from the impact point
near the center that partly condensed into stars.
Pictured below is NGC 922 with its beautifully complex
ring along the left side, as imaged recently by the Hubble Space Telescope.
Observations of NGC 922 with the Chandra X-ray Observatory, however, show several glowing X-ray knots that are likely large black holes. The
high number of massive black holes was somewhat surprising as the gas composition in NGC 922 -- rich in heavy elements -- should have discouraged almost
anything so massive from forming.
Research is sure to
continue. NGC 922 spans about 75,000 light years, lies about 150 million light
years away, and can be seen with a small telescope toward the constellation of
the furnace (Fornax).
