NASA, ESA; P. Kalas and J. Graham (UC Berkeley) and M. Clampin (NASA/GSFC); (inset) Eric Mamajek (University of Rochester) et al.

ScienceShot: A 20-Million-Year Orbit

Located 25 light-years from Earth and shining by its lonesome in the southern sky on October evenings, Fomalhaut is sometimes called "the solitary one." It's a white A-type star, somewhat hotter than the sun, and the 18th brightest star in the night; it harbors a dusty disk (main image) and a planet whose existence is controversial. Now, astronomers report that a little red star (inset, circled), discovered decades ago 5.67° northwest of Fomalhaut, shares the same distance and motion through space. Thus, as the scientists will announce in a future issue of The Astronomical Journal, the dim red sun probably revolves around the bright white star, even though the two are separated by a whopping 2.5 light-years of space, which is more than half the distance between the sun and Alpha Centauri, the nearest star system to our own. The astronomers calculate that completing a single orbit takes the red dwarf roughly 20 million years. Fomalhaut possesses another distant companion, an orange dwarf named Fomalhaut B, so the discovery means this famous star is a triple system with two of the farthest-flung stellar companions ever seen. And that suggests that widely spaced star systems are more common than astronomers previously thought. Meanwhile, the little red star, which bears the prosaic name LP 876-10, is in for an upgrade: The researchers recommend it be rechristened Fomalhaut C.

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