AAO image reference AAT 109. « Previous || Next »
Top left is NE. Image width is about 4 arc min
Image and text © 1991-2010, Australian Astronomical Observatory, photograph by David Malin.
Planetary nebulae present a wide variety of forms on the sky, partly because of the random orientation of their parent stars but also because the nebulae themselves can have quite different intrinsic shapes. Theories about the shapes of planetaries range from the influence of binary companions to the central star to the distribution of material around the stars during its red giant phase, before the final outburst.
Whatever the mechanism, most planetaries are symmetrical about one or more axes and only rarely do they appear curved like NGC 2899 in Vela. A possible explanation is that the star from which the nebula was ejected had a large proper motion through space. The resulting nebula has the same velocity but vastly lower density than the star so is distorted by its encounter with the tenuous interstellar medium. Distance to planetary nebulae are usually uncertain, but in this case it seems to be about 3000 light years.
For details of photographic exposure, search technical table by AAT reference number.
| emission nebulae
| reflection nebulae
| dark nebulae
| planetary nebulae
| star clusters
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