Ten Space Telescopes in Order of Launch

Hubble has orbited Earth since 1990. A flaw in its main mirror was found after launch and corrected by a 1993 Space Shuttle servicing mission, after which it returned some of the most detailed images of distant galaxies and helped refine the measured expansion rate of the universe.

Launched on 7 April 1991 and named for the physicist Arthur Holly Compton, it detected photons from 20 keV to 30 GeV. It found gamma-ray bursts coming from every direction of the sky rather than clustering in the Milky Way, and was deliberately deorbited in 2000.

Launched in 1999, Chandra sees X-rays, which Earth's atmosphere absorbs, so no ground instrument can. Named for Subrahmanyan Chandrasekhar, it is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope.

The European Space Agency launched XMM-Newton in 1999, the same year as Chandra, and named it for Isaac Newton. It is an X-ray observatory with very large mirrors, used to study black holes, neutron stars and hot gas in galaxy clusters.

Launched on 25 August 2003 as the Space Infrared Telescope Facility, Spitzer observed in infrared light from an Earth-trailing solar orbit until 2020, with its instruments cooled to 5.5 kelvin. In 2016 it found five of the seven known TRAPPIST-1 planets.

Launched on 20 November 2004 aboard a Delta II rocket, Swift is built to turn rapidly toward a gamma-ray burst and watch its afterglow in X-ray, ultraviolet and optical light. It was renamed in 2018 for its long-time principal investigator Neil Gehrels.

Fermi studies gamma rays from low Earth orbit and began operating in 2008 under the name Gamma-ray Large Area Space Telescope. It targets pulsars, active galactic nuclei and gamma-ray bursts, and in 2010 announced two gamma-ray and X-ray emitting bubbles around the Milky Way.

Launched in 2009, Kepler orbited the Sun to avoid Earth occultations and stray light. Its single photometer watched the brightness of about 150,000 stars for the small dips caused by planets crossing them, confirming thousands of exoplanets before fuel ran out in 2018.

Launched by the European Space Agency in 2013, Gaia measured the positions, distances and motions of nearly two billion stars from near the Sun-Earth L2 point. Its science observations ended in January 2025, leaving the most detailed three-dimensional map of the Milky Way yet made.

Launched in 2021 and operating from about 1.5 million kilometers away at the Sun-Earth L2 point, Webb has a mirror made of 18 hexagonal segments and observes from long-wavelength visible light through the mid-infrared, letting it see galaxies closer to the early universe than any earlier telescope.