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Beyond Earthly Skies

Capturing Planetesimals from a Passing Star

7 Jul 2015, 23:00 UTC
Capturing Planetesimals from a Passing Star
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A population of far-flung objects orbit the Sun in the outer regions of the Solar System, between the Kuiper belt and the more distant Oort cloud. These objects can be referred to as Sednoids, after 90377 Sedna - the first of its kind to be discovered in 2003. Roughly a dozen or so Sednoids have been detected so far. These objects orbit the Sun at distances of between 150 to 1,500 AU and come no closer than 30 AU to the Sun. They are too far to be Kuiper belt objects, but not far enough to be Oort cloud objects. At present, there is no explanation for how these objects came to be.Figure 1: Artist’s impression of a planetesimal orbiting far from its host star.Sednoids are also intriguing because their orbital inclination with respect to the ecliptic range between 10° to 30°, and their argument of perihelion cluster around 340° ± 55°. The terms “orbital inclination” and “argument of perihelion” are parameters used to describe an object’s orbit around the Sun. Basically, the ecliptic is defined as a plane of reference that is coplanar with Earth’s orbit around the Sun, while the argument of perihelion is the angle between an ...

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