PROPERTIES OF STARS

 

I.               Distances   {relative}

Direct method:    Parallax is the objectís apparent shift relative to some more distant background as the objectís 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 starís 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 Ö

                                           |Ŗ  ī100 ŗ|

 

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

 

 

IV.   Stellar surface temperature and color  {intrinsic}.

 

Photometry: Wienís 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-Boltzmannís 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}