the Sun
For example, the composition of the Sun
- not so far away but impossible to sample visible regions
- T of 6000 K too hot
- every known substance melts and vaporizes
- e.g. iron (Fe) and even tungsten (W)
- Therefore analyze solar spectrum to determine composition
- example He, from Greek Helios
- sun god, drove the sun across the sky in chariot
- seen in solar spectrum, matched no substance known to man
- only in 20th century identified with 2nd most simple atom
- (2 e- orbiting 2 p + 2 n) draw on board & H
- analysis shows lots of He in sun, and even more H:
- for every 1000 atoms of H
- 100 atoms of H
- 1 atom everything else (C, N, O, Ne, Fe, etc.)