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Beyond Earthly Skies

A Star Came Close to the Sun 70,000 Years Ago

17 Feb 2015, 22:00 UTC
A Star Came Close to the Sun 70,000 Years Ago
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The Oort Cloud is a spherical cloud of icy planetesimals that surrounds the Sun out to a distance of about 50,000 AU. For comparison, Pluto’s orbit never brings it further than 49 AU from the Sun. Passing stars can perturb these icy planetesimals in the Oort Cloud and send them on trajectories towards the Sun, resulting in the flux of long-period comets that visit the planetary region of the Solar System. Some of these comets might have even impacted Earth and produced extinction events. A study by Mamajek et al. (2015) reports on the identification of the closest known flyby of a star to the Solar System. The star belongs to a nearby, low-mass binary system known as WISE J0720.A star’s velocity through space consists of two components - radial and tangential. Radial motion is how fast the star appears to be approaching or receding along the line of sight, while tangential motion is the motion of the star across the plane of the sky, perpendicular to the line of sight. WISE J0720 seems peculiar with its low tangential velocity of only ~3 km/s because this suggests that most of its velocity could be in the radial component. Indeed, WISE ...

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