Sun’s closest solo star may have company

Enlarge / The position of Barnard's star relative to the Earth and its other neighbors. (credit: IEEC/Science-Wave/Guillem Ramisa)
From the phenomenal success of the Kepler mission and a proliferation of ground-based telescopes, we now know that planets are common in our galaxy. But the methods we've used to detect most of them are biased toward finding large planets that orbit close to their host stars. The farther a planet is, the less its gravity pulls at the star and the less likely it is to align so that its orbit passes between that star and Earth, thus blocking out some starlight. Meanwhile, the focus has shifted to nearby stars, as astronomers have started building a catalog of targets for the next generation of telescopes.
These issues provide an intriguing backdrop for today's announcement that one of the closest stars to Earth has a super-Earth companion. Barnard's star is a red dwarf that is only six light years from our Solar System; only the three stars of the Centauri system are closer. But the new planet orbits far enough from Barnard's star that it had been missed by earlier attempts. The detailed follow-up that spotted it also hints at the possibility of a separate, more distant planet, and both could help inform our models of planet formation.
A new look
Barnard's star has been observed extensively over the years, partly because it's so close, partly because it's a prototypic example of a red dwarf star. These observations have included exoplanet searches, but nothing about the system stood out. But unless you observe a star regularly, there's a chance you won't happen to be looking at critical points in the planet's orbit.
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