Star Characteristics and Law

Spectral Classes of stars

Balmer strongest spectral class A Electrons start at energy level N-2

Paschen strongest spectral class M Electrons start at energy level N-3

Lyman strongest spectral class O or B Electrons start at energy level N-1

• The stars surface temperature determines the strength of its spectral lines.

The Doppler Effect is the change in frequency of a wave for an observer moving relative to the source of the wave.

The Doppler effect is of intense interest to astronomers who use the information about the shift in frequency of electromagnetic waves produced by moving stars in our galaxy and beyond in order to derive information about those stars and galaxies. The belief that the universe is expanding is based in part upon observations of electromagnetic waves emitted by stars in distant galaxies. Furthermore, specific information about stars within galaxies can be determined by application of the Doppler effect. Galaxies are clusters of stars that typically rotate about some center of mass point. Electromagnetic radiation emitted by such stars in a distant galaxy would appear to be shifted downward in frequency (a red shift) if the star is rotating in its cluster in a direction that is away from the Earth. On the other hand, there is an upward shift in frequency (a blue shift) of such observed radiation if the star is rotating in a direction that is towards the Earth.

For spectral and wavelength comparison see diagrams on page 164 of book.

NEWTON’S LAW’S

First law: An object moves at a constant velocity if there is no net force acting upon it.

Example: