AAO image reference AAT 21. « Previous || Next »
Top left is NE. Image width is about 9 arc min
Image and text © 1980-2010, Australian Astronomical Observatory, photograph by David Malin.
Superficially similar to a planetary nebula, (e.g. the Helix nebula or the 'spiral' planetary ) NGC 6164-5 is in reality a rather unusual object associated with a rather unusual star.
The striking blue central star, known only as HD 148937, is the brightest member of a triple system of stars in orbit around each other. This extremely hot star is losing mass from its outer layers continuously, but occasionally more vigorous outbursts give rise to the symmetrical shells seen in this picture. The two catalogue numbers, NGC 6164 and 6165, refer to these shells as separate objects. The nebula is in the southern Milky Way, in Norma at a distance of about 4200 light years.
Related Images
AAT 27. The faint nebula around NGC 6164-65
Constellation of Norma (external site)
For details of photographic exposure, search technical table by AAT reference number.