Starship Asterisk*

neufer wrote:

Chris Peterson wrote:
Let's just say that the formation of a planetary nebula is a very low-energy event compared with a supernova.

"Excitement" is in in the eye of the beholder.

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I 'see' that Art still likes to keep his eye on things. , he does.

I haven't commented on this one. I have been lazy, and a little bit sick.

Well, this APOD is a very nice portrait of the dust that is first made by a red giant and then spread out into space by the "series of gentle explosions" that creates the planetary nebula.

Ordinary red giants, the ones that come from intermediate-mass stars like the Sun - I refuse to call the Sun a low-mass star when it is more massive than 95% of the stars in the galaxy! - well, these ordinary red giants are responsible for a whole lot of the creation of heavy elements in the universe. Each and every one of the ordinary red giants create heavy elements, for example iron, when they are near the end of their lives. Each red giant creates a moderately small amount of heavy elements, not at all comparable to the fantastic heavy element production of a supernova. But because supernovae are rare, but ordinary red giants are common, it could well be that the total heavy element production by red giants is comparable to the element production by supernovae.

http://en.wikipedia.org/wiki/Stellar_evolution wrote about red giant stars on the brink of becoming planetary nebulae:

Stars in this phase of life are called Late type stars, OH-IR stars or Mira-type stars, depending on their exact characteristics. The expelled gas is relatively rich in heavy elements created within the star and may be particularly oxygen or carbon enriched, depending on the type of the star.

So stars like the progenitor of the Helix Nebula are important creators of heavy elements in the universe, the kind of elements that you need in order to build planets and people.

Out Sun will do the universe this kind of service, too, when it dies. So when the Sun lived, it sustained a living planet, and when it dies, it will give the universe elements to build more planets like the Earth.

Ann