AAO image reference AAT 15b. « Previous || Next »
Top left is NE. Image width is about 35 arc min
Image and text © 2001-2010, Australian Astronomical Observatory, photograph by David Malin.
This faint object is the nearest planetary nebula to the Sun and on deep photographs has a diameter of about half a degree -- the same apparent size as the Sun in the sky. The AAT colour picture shows the fainter parts of the nebula, revealing that the red annulus visible on other images in this series is probably a thick but tenuous shell surrounding the nebula, and appears as a bright annulus where see through a great thickness of it.
To reveal this detail the same original plates used for other images were copied at higher contrast before being combined into a 3-colour image, thus emphasising the fainter parts. The picture above was made without unsharp masking, while the images AAT 15 and AAT 15a were made with the aid of unsharp masks applied to the same plates that produced AAT 15 and AAT 15a. The Helix is in Aquarius, and is about 700 light years away, almost 200 times more distant than the nearest stars.
Related Images
AAT 15. The Helix nebula, with unsharp mask
AAT 15a. The Helix nebula, wide field
AAT 15c. The Helix nebula, unsharp mask, same scale as image AAT 15
Constellation of Aquarius (external site)
For details of photographic exposure, search technical table by AAT reference number.