# 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
* 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
* H$_0$ - 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$_S$, L$_☉$ - luminosity of the Sun
Luminosity of certain object:
* L$_{acc}$ - accretion luminosity
* L$_{bol}$ - bolometric luminosity

## Mass comparison

Mass comparison:
* M$_E$, M$_E$ - mass of Earth
* M$_J$, M$_♃$ - mass of Jupiter
* M$_S$, M$_☉$ - mass of the Sun
Mass of certain object:
* M$_●$ - 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 (﹡) : $[{\ce {Fe/H}}]=\log[{\ce {Fe/H}}]_{*}-\log[{\ce {Fe/H}}]_{\odot }$, 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$_E$, R$_🜨$ - Radius compared to Earth
* R$_J$, R$_♃$ - Radius compared to Jupiter
* R$_S$, R$_☉$ - 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