Skip to comments.Astronomy Picture of the Day 8-4-02
Posted on 08/03/2002 10:54:41 PM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 August 4
Explanation: NGC 2997 is a grand design spiral galaxy. Its small nucleus and sprawling spiral arms give it a type Sc designation. NGC 2997, pictured above, is speeding away from us at about 1100 kilometers per second, which would place it at about 55 million light years distant, given current estimates of the expansion rate of our universe. NGC 2997 is thought to have a mass of about 100 billion times that of our Sun, but is probably less massive than our own Milky Way galaxy. NGC 2997 is not seen face-on - it is thought tilted by about 45 degrees. NGC 2997 is particularly notable for a nucleus surrounded by a chain of hot giant clouds of ionized hydrogen.
Bright, hot young blue stars (massive and short-lived) trace out the spiral structure in such galaxies. Their lives are too short for them to move far from their origin in the dust and gas clouds that make up most of the mass in the arms.
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