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The cometary globule CG 4, wide field

Date created: 2000-05-22

Tags: galaxy, spiral, nebula, dust, reflection


Cometary globules are isolated, faint, relatively small clouds of gas and dust within the Milky Way, many of them in Puppis. Cometary globules were first recognised in 1976 and their faintness makes these objects particularly challenging objects for colour photography. This example is about 1300 light years distant, so the head is some 1.5 light years in diameter, and the tail, which fades away off the picture, appears to be about 8 light years long. The dusty cloud contains enough material to make several Sun-sized stars.

The head of the nebula is itself opaque, but glows because it is illuminated by light from very hot stars nearby, off the left of the photograph. Their energy is gradually destroying the dusty head of the globule, sweeping away tiny particles that scatter the starlight as a faint, bluish reflection nebula. This particular globule also shows a faint red glow, probably from excited hydrogen, and seems about to devour an edge-on spiral galaxy, which in reality is hundreds of millions of light years away, far beyond CG 4.

Photograph made from plates taken in December, 1990.
Top left is NE. Image width is about 30 arc min.

Credit: David Malin

© Australian Astronomical Observatory