Charon (moon)

From Simple English Wikipedia, the free encyclopedia
Charon captured by New Horizons in 2015 true colour.

Charon is a moon of the dwarf planet Pluto. It is half as wide as Pluto and is much like the dwarf planet itself. It was discovered many years after Pluto. They are sometimes considered a binary system, as Charon does not orbit Pluto, and Pluto does not orbit Charon. They orbit a barycentre in space.[1]

Naming[change | change source]

The moon is named after Charon in Greek mythology, a boatman who would carry the souls of dead people across the river Acheron to the underworld.[2]

Discovery[change | change source]

Discovery image of Charon, where the main object is Pluto, and the moon is the odd-looking blob on the edge of the main circle

Charon was found by astronomer James Christy on June 22, 1978, when he was looking at highly blown up picture of Pluto on a photographic plate that taken a couple of months before. Christy noticed that a slight bulge was able to be seen every now and then. This finding was made public on July 7, 1978.[3] Later, the bulge was confirmed on plates dating back to April 29, 1965.

Later observations of Pluto were able to figure out that the bulge was due to a smaller body. The orbit of the bulge fit in with Pluto's rotation period, which was already known from Pluto's light curve.

Any final doubts were erased when Pluto and Charon entered a five-year period of mutual eclipses between 1985 and 1990. This happens when the Pluto-Charon orbital plane is edge-on as seen from Earth, which only happens at twice in Pluto's 248-year orbital period. It was very lucky that one of these intervals happened to occur so soon after Charon's discovery.

Pictures[change | change source]

1996 image of Pluto (left) and Charon (right) from the ESA/Dornier Faint Object Camera on the NASA Hubble Space Telescope.

Pictures showing Pluto and Charon as separate disks were taken for the first time by the Hubble Space Telescope in the 1990s. Later, after a new technology called adaptive optics was discovered, it was possible to see Pluto and Charon as separate disks using ground-based telescopes.

References[change | change source]

  1. C.B. Olkin, L.H. Wasserman, O.G. Franz (2003). "The mass ratio of Charon to Pluto from Hubble Space Telescope astrometry with the fine guidance sensors" (PDF). Icarus. 164 (1): 254–259. Bibcode:2003Icar..164..254O. doi:10.1016/S0019-1035(03)00136-2. Retrieved 2007-03-13.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. "New Horizons: NASA's Pluto-Kuiper Belt Missions". Johns Hopkins University Applied Physics Laboratory. 6 December 2007. Archived from the original on 16 May 2008. Retrieved 1 August 2009.
  3. "IAUC 3241: 1978 P 1; 1978 (532) 1; 1977n". Retrieved 2008-06-22.

Other websites[change | change source]