About the star facts

This page is about how the facts are measured and sourced. The card lines and reflections are our own, written in response to each star: its name and stories, its features, and its place in the sky.

Names

Stars are named as in the International Astronomical Union's Catalog of Star Names, spelled exactly as the IAU records them. Where a star has no proper name, its scientific designation is its name: usually a Greek letter and its constellation, as in Beta Hydri, sometimes a catalogue number, as in 61 Cygni. Clusters, clouds and star patterns, such as the Pleiades or the Dark Emu, keep the names people know them by.

Where a name comes from, and what it meant, is checked against the All Skies Encyclopaedia, a research encyclopaedia of the sky whose star-name pages are mostly written by the etymology group of the IAU's Working Group on Star Names.

Measurements

Distance, brightness and star type are checked against SIMBAD, the astronomical database kept by the Centre de Données astronomiques de Strasbourg, and temperatures come from the published studies it lists. Distances come from parallax, the small shift in a star's position as the Earth travels around the Sun. A star's colour follows from its type.

Every figure is rounded. Astronomy is a science of measured uncertainty, and we would rather say, for example, "about 550 light-years" than claim a precise distance that isn't yet known.

When measurements disagree

Studies of the same star often differ a little. For temperature, we take the middle of the published studies SIMBAD lists, counting each study once, and round it to the nearest 100 kelvin. Where a star has too few studies, or its temperature changes too much for one figure, such as a pulsating star, one well-documented published value is used.

A few facts are genuinely contested. In these cases we adopt one well-documented published value. Betelgeuse, for example, is so large, and its surface so unsettled, that parallax cannot pin it down: its distance, about 550 light-years, is from Joyce and colleagues, 2020. Polaris, at about 430 light-years, follows the Hipparcos satellite rather than the smaller figure a minority of studies prefer.

Double and multiple stars

Many stars that look single are two or more stars held together by gravity. We give their combined light as the brightness, because it's what your eye actually sees. Type and temperature are those of the brightest star.

"System" says how many stars travel together. To count every star the same way, we follow one source: Peter Eggleton and Andrei Tokovinin's 2008 catalogue of companions among all the stars bright enough to see by eye. Only stars held together by gravity are counted, not stars that merely line up when viewed from our perspective, and planets are not counted. Where the catalogue suspects a companion that has not been confirmed, we count only the confirmed stars. Where a later study has settled the question, as for Fomalhaut's third star in 2013, we follow that study.

Across cultures and through history

Cultural notes, a star's names and stories across traditions, are included only where a documented source exists, and they name the people a story belongs to. They are checked against published research and two encyclopaedias: chiefly Wikipedia, each article read at a fixed version along with the studies it cites, and the All Skies Encyclopaedia. If a card has no cultural notes, we could not find a well-documented record.

We welcome feedback, and suggestions for future cultural notes. Please include a documented source, ideally one that can be cross-checked, and write to us.

The artwork

The constellation figures on the card faces and the star patterns on their backs are adapted from the line art of NOIRLab's 88 Constellations project. NOIRLab is the United States' national centre for night-sky astronomy.

Corrections

These facts were last checked in October 2026. If you find an error, please write to us. We check every report against its source and correct the card.

Star names and IAU material are used with attribution under the IAU's Creative Commons licence. SIMBAD is operated by CDS, Strasbourg, France. Constellation line art: NOIRLab, CC BY 4.0, modified.