Gaia in the UK

Taking the Galactic Census

Social stars

Social stars

A third of stars are born and live in pairs or even larger groups. Just like humans, they can considerably influence each others’ lives, as well as the way they influence their environment. Understanding multiple-star-systems is key to understanding stars, the Milky Way, and the Universe.

With data release 3, Gaia has just delivered a comprehensive database astronomers have long been wishing for, including 813 000 binary stars, to answer the many open questions.

This animation illustrates the sky-projected motions of binary stars whose orbits have been determined by Gaia. Each ellipse corresponds to one of 335 systems located within 50 pc (163 light years) and with periods shorter than 1000 days. These are cases where Gaia sees only the motion of one source, which can correspond to the reflex motion of a star due to the gravitational pull of an invisible companion, or to the apparent motion of the combined light from two orbiting stars so close together that Gaia cannot distinguish them.

The orbits are shown to scale and are ordered by increasing distance from the Sun from top-left to bottom-right. The white horizontal line at the bottom-right indicates an apparent size of 10 milli-arcseconds. The colour roughly corresponds to the source's colour as determined by Gaia with purple/blue indicating hot stars and white dwarfs, green/yellow indicating Sun-like stars, and red indicating cool, low-mass stars.

The animation shows the inferred orbital motions over 1000 days, corresponding roughly to the time range covered by Gaia’s data release 3, and the dots indicate the modelled positions of the stellar images after subtracting the effects of proper motion and parallax. The orbits show a range of short and long periods, different sizes, various elliptical shapes, and some are seen edge-on, which limits the apparent motion to a line. Gaia’s data release 3 contains about 500 times more astrometric orbit solutions than the ones shown here.

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Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO.


Page last updated: 13 June 2022