Monday 17 August 2020

Ceres reaches aphelion.

The Dwarf Planet Ceres reached aphelion (the furthest point on its orbit to the Sun) at 8.11 am GMT on Monday 17 August 2020, when it was 2.98 AU (445 749 000 km) from the Sun. This is only 0.42 AU (62 945 000 km) more distant than the planet's perihelion (closest point on its orbit from the Sun), as Venus has one of the least eccentric circular orbits of any body in the Main Asteroid Belt.

The orbits of Ceres, Jupiter, Mars, Earth, Venus and Mercury, and their positions on 17 August 2020. In The Sky. 

Because Ceres is further from the Sun than the Earth, its orbital period is much longer than ours, with the Dwarf Planet completing one obit every 1683 days (4.65 years), on an eccentric orbit tilted at 10.6° to the plane of the Solar System. The orbit of Ceres places it within the inner part of the Main Asteroid Belt, but due to its large size, with a diameter of 939.4 km, it is considered to be a Dwarf Planet rather than an asteroid.

High resolution image of Ceres made on 20 September 2020, by the Dawn Space Probe. Wikimedia Commons/NASA/JPL/Caltech.

Ceres was discovered on 1 January 1801 by Giuseppe Piazzi, a Catholic priest at the Academy of Palermo, Sicily. It was the first body to be discovered in the Main Asteroid Belt, and at the time when it was discovered an international search was underway for a presumed 'missing planet' between the orbits of Mars and Jupiter (although Piazzi was studying stars when he first observed Ceres, and initially presumed he had found a new comet). Ceres was for a long time considered to be the largest asteroid in the Solar System, but in 2006 was re-classified as a Dwarf Planet, as part of a revision of the classification of Solar System bodies driven by the discovery of a growing number of bodies in the Outer Solar System which are too large to be considered asteroids or comets yet to small to be considered to be planets. Of the nine bodies currently classified as Dwarf Planets, only Ceres is located within the Main Asteroid Belt, with five lying in the Kuiper Belt (Orcus, Pluto, Haumea, Quaoar, and Makemake), two lie within the Scattered Disk (Gonggong and Eris), and one within the Detached Region on the outer fringe of the Solar System (Sedna).

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