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Q & A: Sun composition

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Most recent answer: 02/21/2008
What is the sun made up of?
- Mohibullah (age 7)
Pakistan Embassy School Beijing, Beijing,China
The sun is composed largely of hydrogen, and helium is the number-two element (in fact, the name for helium comes from the Greek word for "sun", as the element was first identified by the characteristic dark bands in the solar spectrum). Most atoms in the sun are "ionized" -- the electrons are not bound to the protons in the hydrogen of the sun. So you could think of it mostly as a plasma of protons and electrons held together gravitationally and electrostatically, with radiation pressure holding it up.

That's not the whole story, however. The sun manufactures elements from lighter ones in the process of nuclear fusion. Helium is a byproduct of nuclear fusion, and beryllium, lithium, boron, and other atoms are part of the ordinary fusion process.

Furthermore, the solar system is full of heavy elements. Just look at all the stuff on Earth. I'd imagine any element found on Earth is present in the sun, but not in as much quantity as the hydrogen and helium. Elements heavier than iron are formed in supernovas. The solar system has plenty of these, and so debris from an ancient supernova contributes to the composition of everything in it, including, and especially, the sun.


(published on 10/22/2007)

Follow-Up #1: Hottest part of the sun

Where is the sun hottest?
- Deyanira Mendoza (age 16)
Los Angeles C.A
Right in the center, just like the hottest part of the earth.  The reason is that heat is generated throughout  the sun due to the burning of hydrogen into different light nucleii, mainly helium. See for more detailed information. 
Now this heat has to escape somewhere and that is the surface of the sun.  So the surface of the sun is cooler due to its loss of heat.  There is a thermal gradient from very hot in the center to not as hot at the surface, (which is still pretty hot).


(published on 10/22/2007)

Follow-Up #2: Identification of elements in the Sun

follow up question: how exactly do they determine what elements make up the sun? do they use emission or absorption spectra?
- Tiny Tim (age 8)
seattle wa usa
Both emission and absorption spectral lines are used.  Helium was first discovered by absorption spectra.  There is a very nice web site that explains and shows examples of these effects:


(published on 02/21/2008)

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