How do scientists determine what elements make up a star?

I was watching ';The Universe'; on the History Channel the other day. I know for time sake most programs gloss over certain things to address the main ideas. Can anyway tell me in a simple way how scientists discover what elements make up a star? I know that hydrogen converts to helium and etc. I am just wondering how scientists know that it is hydrogen, for example. Thank you very much!How do scientists determine what elements make up a star?
By the spectra of their light.


Specially the dark absorption lines which are typical of every element.How do scientists determine what elements make up a star?
by the spectrum (frequencies) of the energy given off. All matter, will radiate energy and does so at different frequencies. So by analysizing a spectrum, you can determine the substances that make up whatever you are looking at. Search under ';Spectrum of Elements'; to get more details.
They look at the star's spectrum. It's called a spectral analysis. Different elements give a different chemical fingerprint through spectral analysis.


See below
They look at the light coming from the star through a prism. The shade of the red shifted light indicates what gas the star is made up from.
spectral analysis: I forget the specifics, but it is something to the effect that each element produces different wavelengths of light. If you can measure the light you can find would what elements are producing the light.
spectral analysis.





http://imagine.gsfc.nasa.gov/docs/scienc鈥?/a>





Different elements give different spectral lines when tested - this is how Helium was discovered. People knew it was there but couldnt prove it in chemical experiments because Helium is so inert.
Extracting samples from the stars (very unlikely) , or collecting particles given off by the star which is the most likely way. There also may be rock samples on earth from stars, they can analyze them.





//Frankie