Re: Is the nebula that made our sun still there?

When you ask, "Is the nebula that made our Sun still there?", I guess you mean can you still see it. Well, to see part of it, just look at the end of your nose. Yes, the end of your nose. Your nose, the computer you're using right now, the Earth, the planets, asteroids, comets and everything else we can see in our solar system were once part of a nebula.

When some old stars die they explode in what we call "planetary nebulae" (nothing to do with planets, it is just a historical name) or supernovae. In this explosion vast quantities of the material that made up the dying star are blown out into space at high speeds. As these gases pass through the interstellar medium they become excited and glow. We can see remnants of these explosions in nebula like the Cygnus Loop. ( http://ftp.seds.org/pub/images/hst/CygnusLoop.jpg )

Eventually after thousands of years these gases finally come to rest, along with remnants of other stellar explosions. When astronomers turn their telescopes to the heavens, these now cool clouds of gases and other stellar debris are sometimes illuminated by nearby stars, producing reflection nebulae, like the Orion Nebula ( http://www.iexp.com/3/science/astronomy/images/OrionMos.jpg ).

Other times, when no stars nearby illuminate these clouds, they actually absorb light coming from stars beyond them yielding dark nebula like Barnard 86 in Sagittarius ( http://www-hpcc.astro.washington.edu/mirrors/aao/aat092.gif ).

Now suppose another star explodes nearby one of these cloud remnants. The shock wave from this new explosion can compress materials in our dark nebula into cosmic blobs that begin to contract due to gravity. Things really speed up now. Protostars and planets begin to form. If there is enough mass in this proto system, a star or stars will ignite. We can see evidence of new stars forming in the Pleiades ( http://orangutan.cv.nrao.edu/images/astro/pleiades.gif ). Planets may form instead and maybe after several billion years, someone will be sitting on one of those planets asking about nebulae.

Note added by the moderator:

If by nebula, you mean the gas cloud that led to the formation of the Solar Sytem, it no longer exists. Any gas that did not condense into planets, or the Sun, has long ago been swept away by the solar wind if it was reasonably close to the Sun to begin with, or simply dissipated in the interstellar environment due to various shocks from exploding stars and gravitational disturbances from stars and galactic spiral arms passing us by.

Marc Herant, astro moderator