The catalogs that turn the sky into data: Gaia and exoplanets

The sky is studied through observations that must later be located, compared, and reused. Catalogs serve as scientific infrastructure in that work: they describe which objects have been recorded and what kinds of information accompany them. Two institutional examples are the European Space Agency’s Gaia Data Release 3 (DR3) and NASA’s Exoplanet Catalog. They are not equivalent lists: Gaia provides a broad collection of data about celestial sources, while NASA’s resource brings together information on confirmed exoplanets.

Gaia DR3: a data release, not a single list

ESA released Gaia DR3 on June 13, 2022. It expanded on the earlier Early Data Release 3 (EDR3), released on December 3, 2020, combining previously published products with new ones, including data on extended objects and non-single stars. The agency’s documentation emphasizes that the described products use the same time span and set of observations.

Among the EDR3 data incorporated into DR3 are astrometric solutions for about 1.46 billion sources. An astrometric solution can include position on the sky, parallax, and proper motion; some objects have five parameters and others six, with the latter including an additional parameter called pseudocolour. Two-position solutions are also provided for about 344 million additional sources. The G, G_BP, and G_RP magnitudes cover approximately 1.806 billion, 1.54 billion, and 1.55 billion sources, respectively, according to ESA’s summary.

From positions to physical properties

DR3 adds information derived from spectra and classifications. ESA reports object classifications for 1.59 billion sources and astrophysical parameters based on BP/RP spectra for 470 million objects. Products include spectral types, parameters for different classes of stars, mass and age estimates for 128 million stars, and mean BP/RP spectra for 219 million sources. Astrophysical parameters from RVS spectra are listed for 5.5 million objects; the release also includes mean radial velocities for 33 million stars.

These figures describe what the release contains; they do not guarantee that every source has every parameter or that every measurement has identical quality. ESA’s page itself lists different solutions and products with different coverage. It would therefore go beyond the available documentation to treat a total count as though it represented a uniform set of fully characterized objects.

A different catalog for planets around other stars

NASA’s resource has another purpose: it presents data on exoplanets—planets orbiting stars other than the Sun—that the page describes as confirmed. The page says the encyclopedia is continuously updated and contains more than 6,000 entries. It allows users to filter by planet type, discovery method, or the mission or facility that found a planet, and provides interactive visualizations and data for each world. The categories it explains include rocky terrestrial planets, super-Earths, Neptune-like worlds, and gas giants. The page’s captions also identify some illustrations as artist’s concepts.

The page consulted also displayed entries with a 2026 discovery date, including TOI-426 b and TOI-426 c. Their appearance in the catalog is a fact about the page, not independent news coverage of the announcement of those planets. The material available here does not provide details of the studies that led to confirmation of each entry or allow their methods and results to be assessed. Because the catalog is continuously updated, its total should be understood as changing rather than as a permanent count.

What the catalogs show—and what remains open

The useful comparison is not which catalog is “better,” but which question each one is designed to organize. Gaia DR3 documents a wide range of measurements and products for celestial sources; NASA offers a structured reference for exploring confirmed exoplanets. Their scales and units also differ: Gaia reports sources and products with varying coverage, while NASA counts planetary entries. Those totals should not be added together or treated as equivalent.

The available information also does not present a new scientific result directly connecting the two collections. Bibliographic references linked from the Gaia page are clues to publications, but the ESA summary is the basis here for describing DR3; article titles or identifiers alone are not enough to attribute findings to those papers. In short, catalogs map what has been recorded and how it is organized: powerful tools for looking up and comparing information, but always bounded by their definitions, coverage, and update practices.