List of common astronomy symbols explained

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
• cz - apparent radial velocity
• z - Redshift
• μ - proper motion
• π - parallax
• J - epoch
• α - Right Ascension
• δ - Declination
• λ - Ecliptic longitude
• β - Ecliptic latitude
• l - Galactic longitude
• b - Galactic latitude

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 of the Sun

Luminosity of certain object:

• L_acc - accretion luminosity
• L_bol - bolometric luminosity

Mass comparison

Mass comparison:

• M_E, - mass of Earth
• , - mass of Jupiter

Mass of certain object:

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

Metallicity comparison

Metallicity comparison:

• [Fe/H] - Ratio of Iron to Hydrogen. This is not an exact ratio, but rather a logarithmic representation of the ratio of a star's iron abundance compared to that of the Sun.
  • for a given star (﹡) : $[\backslash ce\{Fe/H\}]\; =\; \backslash log[\backslash ce\{Fe/H\}]\_*\; -\; \backslash log[\backslash ce\{Fe/H\}]\_\backslash odot$, where the values represent the number densities of the given element.
• [M/H] - Metallicity ratio.
• Z - Metallicity
• Z_☉, Z_S - Metallicity of the Sun

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 or T - orbital period
• a - semi-major axis
• b - semi-minor axis
• q - periapsis, the minimum distance
• Q - apoapsis, 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
• , - Radius compared to Jupiter
• R_S, - Radius compared to The Sun

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

Notes and References

1. https://arxiv.org/abs/astro-ph/0611040 Ultra-luminous X-ray sources: X-ray binaries in a high/hard state?