Planetary Nebula
An expanding shell of ionized gas ejected from a red giant star in the late stages of stellar evolution. Despite the name, it has no connection to planets. The glowing gas is illuminated by the hot core of the dying star.
Source: science.nasa.gov
APODs including "Planetary Nebula"
Henize 3-401: An Elongated Planetary Nebula
31/07/2002
How do dying stars eject their outer layers? Stars that create elegant planetary nebulas like Henize 3-401, pictured above, are not unusual, causing speculation that, one day, our own Sun may look like this. Henize 3-401 is one of the most elongated planetary nebulas yet discovered, a particularly odd feat for a seemingly round star. Perhaps, some astronomers hypothesize, the elongated shape gives a clue to the expulsion mechanism. Genesis hypotheses include that the outer layers of gas are funneled out by the star's own magnetic field, and that a second unseen star is somehow involved. After the gas disperses in a few thousand years, only a white dwarf star will remain. Henize 3-401 lies about 10,000 light years away toward the constellation of Carina.