List of common astronomy symbols

This is a compilation of symbols commonly used in astronomy, particularly professional astronomy.

Age (stellar)

• τ - age

Astrometry parameters

Astrometry parameters

• R_v - radial velocity
• μ - proper motion
• π - parallax
• J - epoch

Cosmological parameters

Cosmological parameters

• h - dimensionless Hubble parameter
• H₀ - Hubble constant
• Λ - cosmological constant
• Ω - density parameter
• ρ - density
• ρ_c - critical density
• z - redshift

Distance description

Distance description for orbital and non-orbital parameters:

• d - distance
  • d - in km = kilometer
  • d - in mi = mile
  • d - in AU = astronomical unit
  • d - in ly = light-year
  • d - in pc = parsec
  • d - in kpc = kiloparsec (1000 pc)
• D_L - luminosity distance, obtaining an objects distance using only visual aspects

Galaxy comparison

Galaxy type and spectral comparison:

• see galaxy morphological classification

Luminosity comparison

Luminosity comparison:

• L_S - luminosity compared to the Sun (Sol)
• L_☉ - luminosity compared to the Sun (Sol)

Luminosity of certain object:

• L_acc - accretion luminosity
• L_bol - bolometric luminosity

Mass comparison

Mass comparison:

• M_E - mass compared to Earth
• M_⊕ - mass compared to Earth
• M_J - mass compared to Jupiter
• M_♃- mass compared to Jupiter
• M_S - mass compared to the Sun (Sol)
• M_☉ - mass compared to the Sun (Sol)

Mass of certain object:

• M_●^[1] - mass of black hole
• M_acc - mass of accretion disc

Metallicity comparison

Metallicity comparison:

• Fe/H - Iron ratio to Hydrogen, a logarithm representation of the ratio of a star's iron abundance compared to that of the Sun
• M/H - Metallicity ratio.
• Z - Metallicity
• Z_S - Metallicity compared to the Sun (Sol)
• Z_☉ - Metallicity compared to the Sun (Sol)

Orbital parameters

Orbital Parameters of a Cosmic Object:

• α - RA, right ascension, if the Greek letter does not appear, á letter will appear.
• δ - Dec, declination, if the Greek letter does not appear, ä letter will appear.

• P or P_orb - orbital period
• a - semi-major axis
• b - semi-minor axis
• q - periapsis, the minimum distance
• Q - apsis, the maximum distance
• e - eccentricity
• i - inclination
• Ω - longitude of ascending node
• ω - argument of periapsis

• R_L - Roche lobe
• M - Mean anomaly
• M_o - Mean anomaly at epoch

Radius comparison

Radius comparison:

• R_E - Radius compared to Earth
• R_⊕- Radius compared to Earth
• R_J - Radius compared to Jupiter
• R_♃- Radius compared to Jupiter
• R_S - Radius compared to The Sun (Sol)
• R_☉ - Radius compared to The Sun (Sol)

Spectral comparison

Spectral comparison:

• see Stellar classification
• m_(object) - Apparent magnitude
• M_(object) - Absolute magnitude, for galaxies and stars
• H_(object) - Absolute magnitude, for planets and nonstellar objects

Temperature description

Temperature description:

• T_eff - Temperature Effect, usually associated with luminous object
• T_max - Temperature Maximum, usually associated with non-luminous object
• T_avg - Temperature Average, usually associated with non-luminous object
• T_min - Temperature Minimum, usually associated with non-luminous object
• K - Kelvin

See also

• List of astronomy acronyms
• Astronomical symbols
• Stellar classification
• Galaxy morphological classification
• List of astronomical catalogues
• Glossary of astronomy

References