PROPERTIES OF STARS

I.               Distances   {relative}

Direct method:    Parallax is the object’s apparent shift relative to some more distant background as the object’s vantage point changes.

Celestial parallax is one-half of the angle formed at the celestial body by two intersecting lines drawn from the ends of a baseline.

Indirect method:         Distance ladder-chain of the interlocking methods that begin in the Solar system.

II.         Stellar velocities    {relative}

Direct method: observation of the proper motion.

Indirect method: Doppler effect for radial (recession) velocity.

III.    Luminosity {intrinsic}.

Apparent brightness {relative}.

Physical scale:

Luminosity = absolute brightness, is the total amount of energy radiated into space each second from star’s surface.

Apparent brightness = energy flux, is the amount of energy striking some light-sensitive device on Earth per unit time.

Inverse square law:    

Magnitude scale:

Apparent magnitude: -1  0  1  2  3  4  5  6  7  8  9 …

                                           |ß  ´100 à|

Absolute magnitude:  is the apparent magnitude from the distance of 10pc.

IV.   Stellar surface temperature and color  {intrinsic}.

Photometry: Wien’s law, color index.

Spectroscopy: Analysis of intensities of absorption lines.

Spectral classes:

 O[30,000K] B[20,000K] A[10,000K] F[7,000] G[6,000] K[4,000] M[3,000]

V.         Stellar sizes     {intrinsic}

Direct method: observation of the angular size of a star.

Indirect method: Stefan-Boltzmann’s law.

Radius-Luminosity-Temperature relation:

VI.   Stellar masses and composition     {intrinsic}

Direct method: binary stars

Indirect method:

Mass-radius relation:              

Mass-luminosity relation:       

VII.                      Stellar lifetimes     {intrinsic}