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where s<sub>0</sub> is the standard distance. This distance is ten parsecs, or about 2,062,650 AU.
where s<sub>0</sub> is the standard distance. This distance is ten parsecs, or about 2,062,650 AU.
Brightness declines with the square of distance, and squares correpond to doubling of logarithms. One must then multiply that result by 2.5 to stay within the magnitude scale.
Brightness declines with the square of distance, and squares correspond to doubling of logarithms. One must then multiply that result by 2.5 to stay within the magnitude scale.
== Stellar colors and spectra ==
== Stellar colors and spectra ==
# It can provide information on the star's radial velocity vis-à-vis the earth.
# It can provide information on the star's radial velocity vis-à-vis the earth.
To accomplish the latter, astronomers note the placement of various lines in the spectrum and then determine the star's likely constituent elements from the spacing of those lines. Lines that are out of ''place'' are shifted, either toward the blue or toward the red. Nearly all stellar spectrum are shifted toward the red; this [[redshift]] indicates a recession, either of the star or of the part of space where the star resides.<ref>Some [[cosmology|cosmological]] models call for an expansion of space itself, not merely the matter in it. According to these models, a redshifted star is in a part of space that was still expanding as the incident light was generated.</ref>
To accomplish the latter, astronomers note the placement of various lines in the spectrum and then determine the star's likely constituent elements from the spacing of those lines. Lines that are out of ''place'' are shifted, either toward the blue or toward the red. Nearly all stellar spectra are shifted toward the red; this [[redshift]] indicates a recession, either of the star or of the part of space where the star resides.<ref>Some [[cosmology|cosmological]] models call for an expansion of space itself, not merely the matter in it. According to these models, a redshifted star is in a part of space that was still expanding as the incident light was generated.</ref>
=== Spectral types ===
=== Spectral types ===
|-
|-
! Class
! Class
! Temperature
! [[Temperature]]
! Color
! Color
! Elements
! [[Element]]s
! Notes
! Notes
|-
|-