Nebula
A nebula is a giant cloud of gas (mostly hydrogen and helium) and cosmic dust situated between stars in the interstellar medium. Nebulae serve as sites of stellar birth and death—including emission nebulae that glow from ionized gas, reflection nebulae that scatter starlight, and dark nebulae that obscure background stars.
Source: science.nasa.gov
APODs including "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.