Where to find open astronomy data

Most of the data from the world’s large telescopes and space missions is public. Some is released immediately; some after a period of exclusive use by the scientists who proposed the observations, usually between six months and a year. Anyone can download it, and much of the research published each year uses data taken by someone else, often years earlier. This is a guide to the main archives and what each one holds.

Space telescopes

MAST, the Mikulski Archive for Space Telescopes ↗

Run by the Space Telescope Science Institute. Holds Hubble, JWST, Kepler, K2, TESS, GALEX and the Pan-STARRS survey, among others. TESS and Kepler data have no exclusive-use period, and their light curves are the standard starting point for transit work.

IRSA, the NASA/IPAC Infrared Science Archive ↗

Infrared and time-domain surveys: WISE and NEOWISE, Spitzer, 2MASS, and the Zwicky Transient Facility’s public data releases.

HEASARC ↗

NASA’s archive for high-energy astrophysics at Goddard Space Flight Center: X-ray and gamma-ray missions such as Swift, Fermi, NICER and XMM-Newton.

ESA Gaia Archive ↗

Positions, distances, motions, brightnesses and colours for nearly two billion stars from the Gaia mission. Gaia DR3, released in 2022, is the current catalogue, and DR4 is planned for December 2026. Gaia’s distances underpin the sizes of most known stars, and so of the planets around them.

Ground-based surveys and observatories

Sloan Digital Sky Survey ↗

Imaging of a third of the sky and spectra of millions of stars, galaxies and quasars, in regular public data releases with their own query tools.

ESO Science Archive ↗

Raw and processed data from the European Southern Observatory’s telescopes, including the Very Large Telescope, generally public after a one-year proprietary period.

Vera C. Rubin Observatory ↗

The Legacy Survey of Space and Time will image the whole southern sky every few nights for ten years. Its alerts of changing objects are public worldwide; its full data releases go first to scientists with data rights.

Catalogues and reference services

CDS, Strasbourg ↗

SIMBAD, a reference database of astronomical objects and the literature about them; VizieR, which holds tens of thousands of published catalogues and tables; and Aladin, a sky atlas that overlays them on survey images.

NASA Exoplanet Archive ↗

The catalogue of confirmed exoplanets and their measured properties, with the TESS and Kepler candidate lists.

ExoFOP ↗

The Exoplanet Follow-up Observing Program: where observers share imaging, spectra and notes on TESS candidates, so the community does not repeat work.

Tools for getting the data

• Astropy, the community Python library for astronomy: units, coordinates, FITS files, tables and time.
• astroquery, an Astropy-affiliated package that queries MAST, Gaia, IRSA, SIMBAD, VizieR and many other archives from Python.
• lightkurve, a Python package for searching, downloading and analysing Kepler and TESS light curves.
• TOPCAT, a desktop program for exploring and joining large catalogues.

Why it matters

Open archives mean a result can be checked by anyone with the same data, and that old observations keep their value. Neptune was found in 1846 by taking measurements astronomers already had more seriously than anyone before, as described in How Le Verrier found Neptune. The archives above are the modern version of those records, and they are far larger than anyone has had time to read.