90482 orcusとは 意味・読み方・使い方

90482 Orcus is a large Kuiper belt object (KBO) with a large moon and is probably a dwarf planet. It was discovered on February 17, 2004 by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. Precovery images as early as November 8, 1951 were later identified. Orcus is a plutino, locked in a 3:2 resonance with Neptune, making two revolutions around the Sun, while Neptune makes three. This is much like Pluto, except that its orbit is constrained to always be in the opposite phase of its orbit from Pluto: Orcus is at aphelion when Pluto is at perihelion and vice versa. Because of this, along with its large moon Vanth that recalls Pluto's large moon Charon, Orcus has been seen as the anti-Pluto. This was a major consideration in selecting its name, as the deity Orcus was the Etruscan equivalent of the Roman Pluto, and later became an alternate name for Pluto.