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Space telescope, founded 2013

Gaia (ESA)

ESA's Gaia measured positions, distances and motions of about 1 billion objects before retiring in 2025. Its DR4 data release opens December 2, 2026.

Location
Retired (operated at Sun-Earth L2)
Focus
Stars, Galaxies, Dark matter, Exoplanets, Telescopes and missions
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In space

Retired (operated at Sun-Earth L2)

Gaia is the European Space Agency’s astrometry mission: it measured where stars are, how far away they are and how they move. It launched on December 19, 2013, on a Soyuz-Fregat from Kourou and observed from near the Sun-Earth L2 point. Science observations ended on January 15, 2025, and the spacecraft was switched off on March 27, 2025. In about a decade it measured positions, distances and motions for about 1 billion objects, roughly 1% of the Milky Way’s stars, at a mission cost of about EUR 740 million.

Flagship instruments

  • Repeated all-sky scans: measuring each star many times reveals tiny shifts in position, the parallax that gives distance and the proper motion that gives velocity across the sky.
  • Data releases: DR3 (June 13, 2022) held information on more than 1.8 billion sources.

Recent results

The Gaia mission paper (2016) is one of the most used references in astronomy. Gaia data revealed Gaia-Enceladus, the galaxy that merged with the Milky Way about 10 billion years ago (2018), anchored the 2022 Cepheid measurement of the Hubble constant and fed the 2025 study of the Milky Way and Andromeda’s future. In 2026 the Kavli Prize in Astrophysics went to Vasily Belokurov, Amina Helmi and Rodrigo Ibata for Gaia-based work on the Milky Way’s merger history, and Hubble pushed that history back further with the earliest known merger, 11.8 billion years ago.

What to watch, 2026-2030

  • December 2, 2026: Gaia DR4, covering the first 5.5 years (66 months) of data, expected to include the first large set of astrometric exoplanet candidates. The archive closes from November 25 to prepare.
  • 2030 or later: the final release, DR5, not expected before the end of 2030.

Why scientists are converging here

Gaia is the reference frame for almost everything else. In our Research Pulse count, “Gaia” appeared in 501 astro-ph abstracts from April to September 2026, about the same as the 493 in the previous six months: steady, heavy use rather than a spike. DR4 may change that, especially for exoplanets and stars.

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