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Lalande 18115

A small, faint red dwarf star, of a kind that is common throughout the Galaxy, but difficult to detect unless a given star lies relatively close to the Sun. In the case of Lalande 18115, the star is indeed in the close neightbourhood of the Solar System, lying just 21.5 light years away. (Many sources suggest a distance of 20.1 light years for this star, but the recent Gaia measurements suggest that it is actually marginally further away than was previously thought.)

In the sky, Lalande 18115 lies in the western parts of Ursa Major, some distance to the west of the Plough formation, and a little to the north of Talitha and Alkaphrah, the stars that mark the Great Bear's forepaws. Despite its close proximity in stellar terms, at just eighth magnitude this star is nonetheless far too faint to be seen with the naked eye.

Cooler and far less luminous than the Sun, Lalande 18115 is also a small star, with a diameter of only about half that of the Sun. It forms a binary system, with an even fainter and less massive star orbiting at a distance of some 110 AU. The two binary components complete a circuit of one another over a period of nearly a millennium.

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