Skip to Main Content


GALEX mission graphic

Galaxy Evolution Explorer

Phase: Past

Launch Date: April 28, 2003

Mission Project Home Page -

Program(s):Astrophysics Explorers, Explorers

Pin it

GALEX - Cartwheel Galaxy
Andromeda Galaxy - GALEX images rings of hot, recently born stars in the disk of the Milky Way's neighbor, Messier 31. Far-ultraviolet emission (152 nm) is rendered in blue and near-ultraviolet emission (227 nm) is rendered in orange.
Credit: NASA/JPL-Caltech

The Galaxy Evolution Explorer (GALEX) was an orbiting space telescope that observed galaxies in ultraviolet light. Since its launch in 2003, the mission surveyed hundreds of millions of galaxies in ultraviolet light across ten billion years of time. After nine years of operation, NASA lent the spacecraft to Caltech under a Space Act Agreement between May 2012 and April 2013.

The original NASA mission's science goals included mapping the history of galaxy and star formation in the universe, and performing ultraviolet all-sky imaging and ultraviolet wide-area spectroscopic surveys. Along with its many findings, GALEX provided new and comprehensive evidence for the "nurture" theory of galaxy evolution, which holds that the galaxies first described by Hubble - the elegant spiral and ball shaped elliptical galaxies -- are evolutionarily linked. GALEX is helped to determine the metal production history of galaxies which will in turn, help scientists understand and account for the origins of the stars and their constituent elements that are observed today.

Science Highlights:

  • Discovered a gargantuan comet-like tail behind the speeding star called Mira.
  • Found the remnant of a star shredded by a supermassive black hole.
  • Discovered giant rings of new stars around old, presumed dead galaxies.
  • Discovered "missing link" galaxies intermediate between the major populations of red elliptical galaxies and blue spiral galaxies.
  • Provided independent confirmation of the nature of dark energy.

The NASA GALEX mission was a partnership between NASA's Jet Propulsion Laboratory and the California Institute of Technology (Caltech) and included other universities, science institutes, laboratories, and commercial technology providers from around the world. Caltech in Pasadena, California, hosts the GALEX science center and has overall responsibility for the project. JPL in Pasadena, California, constructed the GALEX science instrument, performed calibration, and was responsible for project management.