Starship Asterisk*

by **mexhunter** » Mon Sep 27, 2010 2:56 am

Congratulations to Derek Santiago for this APOD.
Greetings
César

by **neufer** » Sat Sep 25, 2010 10:27 pm

Ann wrote:
neufer wrote:
Hydrogen & oxygen are well separated inside Red Giant stars prior to supernova explosion:
http://en.wikipedia.org/wiki/Stellar_nucleosynthesis
Art, Art, Art. Red giants don't explode as supergiants [sic].

Arcturus, a typical red giant ... is not going to explode as a supernova.

Well, Ann, Ann, Ann,
there are low mass Red Giants (0.5–2.57 solar masses) & high mass Red Giants (2.57–10 solar masses).

I was just reading the slide above which, no doubt,
refers ONLY to high mass Red Giants (2.57–10 solar masses).

http://en.wikipedia.org/wiki/Red_giant wrote:
<<In stars massive enough to ignite helium fusion, an analogous process occurs when central helium is exhausted and the star switches to fusing helium in a shell, although with the additional complication that in many cases hydrogen fusion will continue in a shell at lesser depth. This puts stars onto the asymptotic giant branch, a second red giant phase. More massive stars continue to repeat this cycle, fusing heavier elements in successive phases, each lasting more briefly than the previous.

A solar mass star [like Arcturus] will never fuse carbon. Instead, at the end of the asymptotic giant branch phase, the star will eject its outer layers, forming a planetary nebula with the core of the star exposed, ultimately becoming a white dwarf. The ejection of the planetary nebula finally ends the red giant phase of the star's evolution.

The red giant phase typically lasts only a few million years and hence is very brief compared to the billions of years that stars of roughly solar mass will spend on the main sequence.>>

by **Ann** » Sat Sep 25, 2010 8:28 pm

Art wrote:

Hydrogen & oxygen are well separated inside Red Giant stars prior to supernova explosion:

Art, Art, Art. Red giants don't explode as supergiants.

Arcturus, a typical red giant although shown here in exaggerated, too-red color. It is not going to explode as a supernova.

Boiling, misshaped red (but not this red) supergiant Betelgeuse. It will probably explode as a supernova.

Even blue supergiants may go supernova. Just look at that Sanduleak whatever its number was that went ka-boom in the Large Magellanic Cloud.

There used to be a blue star here, before it went poof.

Ann

by **mexhunter** » Sat Sep 25, 2010 4:25 pm

neufer wrote:
mexhunter wrote:Hi Art:
Often I lose myself, like now.
What relationship has "Jeep" with Melotte 15?
It's just curiosity.
Greetings
Hi César,

Look carefully right in the middle of Melotte 15 and you should be able to see
the Jeep (his head has all but disappeared with the exception of his nose):
Melotte 15 in the Heart

Thank you very much.
Regards
César

by **León** » Sat Sep 25, 2010 4:19 pm

neufer wrote:
León wrote:The abundance of hydrogen and oxygen tells me, personally, which is water broken down into its elements by radiation.
Hydrogen & oxygen are well separated inside Red Giant stars prior to supernova explosion:
http://en.wikipedia.org/wiki/Stellar_nucleosynthesis
Where do they find the time to form water before being broken back down by radiation?

Water on the Sun?

________
Researchers Confirm that Water Exists On The Sun

Press Release no. 115 -- July 17, 1997
University of Waterloo

WATERLOO, Ont. -- An international team of scientists, including a University of Waterloo chemistry professor, has conclusively demonstrated that water (actually steam) does exist on the sun, confirming a breakthrough finding made two years ago.

The team used an innovative method to calculate the water spectrum at sunspot temperatures. The method will be useful in modelling systems with an abundance of extremely hot water molecules, such as forest fires.

In their 1995 study, the team recorded evidence of water -- not in liquid form because the sun is too hot, but as vapor or steam -- in dark sunspots. The scientists compared the laboratory infrared spectrum of hot water with that of a sunspot.

The water in the sunspots causes a sort of "stellar greenhouse effect" that affects the sunspot's energy output. Hot water molecules are also the most important absorbers of infrared radiation in the atmospheres of cool stars, such as "variable red giants."

by **neufer** » Sat Sep 25, 2010 2:02 pm

León wrote:The abundance of hydrogen and oxygen tells me, personally, which is water broken down into its elements by radiation.

Hydrogen & oxygen are well separated inside Red Giant stars prior to supernova explosion:

: http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

Where do they find the time to form water before being broken back down by radiation?

by **León** » Sat Sep 25, 2010 1:36 pm

The abundance of hydrogen and oxygen tells me, personally, wich is water broken down into its elements by radiation.

by **orin stepanek** » Sat Sep 25, 2010 12:24 pm

You're looking at Melotte15 in the Heart Nebula. This is the Heart nebula. Here you can see it's shape.

by **APOD Robot** » Sat Sep 25, 2010 4:00 am

Melotte 15 in the Heart

Explanation: Cosmic clouds seem to form fantastic shapes in the central regions of emission nebula IC 1805. Of course, the clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are near the center in this colorful skyscape, along with dark dust clouds silhouetted against glowing atomic gas. A composite of narrow and broad band telescopic images, the view spans about 40 light-years and includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the constellation Cassiopeia.

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