Starship Asterisk*

APOD Robot wrote: Shapley 1: An Annular Planetary Nebula

Explanation: What happens when a star runs out of nuclear fuel? For stars about the mass of our Sun, the center condenses into a white dwarf while the outer atmospheric layers are expelled into space and appear as a planetary nebula. This particular planetary nebula, pictured above and designated Shapley 1 after the famous astronomer Harlow Shapley, has a very apparent annular ring like structure. Although some of these nebulas appear like planets on the sky (hence their name), they actually surround stars far outside our Solar System.

Georges'assistant wrote:Why is the center open ?
All these planetary nebulas seems like shorts cylinders with the axis orieted to us.
Are they really cylindres with the open side looking to us?
Or are they spheres that look thin in the center and with more depth in the peripheral circle ?
Thanks.

orin stepanek wrote:
Kind of like looking down a barrel. The opening is pointed right toward us!

• But aren't we are pointing the barrel of a telescope at Shapley 1
  Click to play embedded YouTube video.

Dick Stacy wrote:If the parent star was spherical, why isn't the nebula ?

Wolf kotenberg wrote:must be supernovae remnant week at APOD. Easy chair + ice cold one + APOD = an insignificant one salutes you