A cosmic census of the currently known objects in the vicinity of our sun has revealed that there are 540 stars and planets in the immediate neighbourhood.
Using existing databases of objects alongside data from the European Space Agency’s Gaia telescope, which is mapping billions of stars in our galaxy, Céline Reylé at the UTINAM Institute in France and her colleagues pooled all knowledge of objects within 10 parsecs, or 33 light years, of our sun.
While previous surveys have counted the stars in this region, no complete census has been made of the known other objects here too. These include planets and brown dwarfs, which are failed stars that never quite grew large enough to ignite nuclear fusion in their cores.
The total count reveals 540 known objects, not counting the sun and the eight planets of the solar system. That number includes 375 stars, 88 brown dwarfs and 77 exoplanets. “This list is as volume-complete as possible from current knowledge,” the team says in the paper describing the work.
Of the stars in the census, 249 are small red dwarfs like Proxima Centauri, our closest neighbour at 4.2 light years away. There are also 21 white dwarfs, dense cores left behind by some dead stars, 18 G-type stars like our sun, and two stellar systems containing five stars each.
While the number of stars is thought to be fairly accurate, there could be dozens more brown dwarfs that so far are too faint to spot. And the number of planets is very much a preliminary figure – our methods of finding them so far have been limited, but most of the stars should have at least several planets in orbit.
Mapping objects out to a distance of 10 parsecs is useful, as it can give us a benchmark for the similar ratio of objects in the rest of the galaxy. “It’s a golden sample for further observation,” says Reylé.
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