Charon (moon)

Encyclopedia : C : CH : CHA : Charon (moon)

---

---

 

Charon

Pluto and Charon
Discovery
Discovered by	James W. Christy
Discovered on	June 22, 1978
Space Missions	New Horizons flyby mission to Pluto and Charon
Orbital characteristics
Semimajor axis	19 571 ± 4 km
Eccentricity	0.00000 ± 0.00007
Orbital period	6.387230 d (6 d 9 h 17 m 36 s)
Inclination	115.60° (to the ecliptic) 0.00° ± 0.014° (to Pluto's equator) 122.54° (to Pluto's orbit)
Is a satellite of	Pluto
Physical characteristics
Mean diameter	1212 km ± 3 km (0.095 Earths)
Mass	kg (2.5445 Earths)>
Mean density	1.63 ± 0.07 g/cm3
Surface gravity	0.276 m/s2
Escape velocity	0.578 km/s
Surface Temperature	-220 degrees Celsius (53 K)
Rotation period	synchronous
Axial tilt	zero
Albedo	varies 0.36 to 0.39
Atmosphere	none (< 0.11 μbar or 11 mPa)

Charon (shair'-ən or kair'-ən, IPA /ˈʃɛərən, ˈkɛərən/, Greek Χάρων), or Pluto I, is the largest satellite of Pluto. It was discovered by astronomer James Christy on June 22, 1978 by carefully examining highly magnified images of Pluto on photographic plates taken a couple of months before and noticing that a slight bulge appeared periodically. Later, the bulge was confirmed on plates dating back to April 29, 1965. It received the temporary designation S/1978 P 1, according to the then-recently instituted convention. It is not to be confused with the similarly named 2060 Chiron, another object in the outer solar system with an orbit between those of Saturn and Uranus. With the discovery in 2005 of two other moons of Pluto (Nix and Hydra), Charon is now also referred to as Pluto I.

Due to the unusual similarity in size between Charon and Pluto, they are sometimes considered a double planet. They are also sometimes thought of as the first known trans-Neptunian objects.

Christy chose the name "Charon" for the moon, and this was officially accepted by the IAU in 1985. In Greek mythology, Charon was the ferryman of the dead, a figure with close ties to the god Pluto. The ch of the mythological figure is pronounced as a k sound, like the ch in Christy's name. However, Christy pronounced the ch in the moon's name as an sh sound, after his wife Charlene (nicknamed "Char"). The sh pronunciation is now common among astronomers, in spite of the pleas of classicists.

Charon's diameter is 1,205 km (748.8 miles), just over half that of Pluto, with a surface area of 4,560,000 km². Unlike Pluto, which is covered with nitrogen and methane ices, the Charonian surface appears to be dominated by less volatile water ice.

Charon and Pluto revolve about each other every 6.387 days. The two objects are gravitationally locked, so each keeps the same face towards the other. The average distance between Charon and Pluto is 19,130 km (11,889 mi). The discovery of Charon allowed astronomers to accurately calculate the mass of the Plutonian system, and mutual occultations revealed their sizes. However, neither indicated the two bodies' individual masses, which could only be estimated until the discovery of Pluto's outer moons in late 2005. Details in the orbits of the outer moons reveal that Charon has approximately one-eighth the mass of Pluto. This shows it to have a density of 1.71 g/cc, suggesting a composition of 63% ±5% rock to 37% ice, whereas Pluto is somewhat denser and about 70% rock.

Simulation work published in 2005 by Robin Canup suggested that Charon could have formed by a giant impact around 4.5 billion years ago, much like the Earth and Moon. In this model a large Kuiper belt object struck Pluto at high velocity, destroying itself and blasting off much of Pluto's outer mantle, and Charon coalesced from the debris. However, such an impact should result in an icier Charon and rockier Pluto than we find, and it is now thought that Pluto and Charon may have been two bodies that collided before going into orbit about each other, violently enough to boil off volatile ices like nitrogen but not violently enough to be disrupted.

The moon, along with Pluto, is to be visited by the New Horizons mission in July 2015.

References

External links

Wikimedia Commons has media related to:

[38083 Rhadamanthus | 38628 Huya | 28978 Ixion | 2003 VS₂ | 90482 Orcus

Cubewanos: 1992 QB₁ | 1994 GV₉ | 1994 JQ₁ | 1994 VK₈ | 1996 TO₆₆ | 19521 Chaos | 53311 Deucalion | 2002 AW₁₉₇ | 50000 Quaoar | 2002 MS₄ | 2002 TX₃₀₀ | 2002 UX₂₅ | 1997 CQ₂₉ = 58534 Logos | 2003 AZ₈₄ | 2003 EL₆₁ | 2003 QW₉₀ | 2005 FY₉

Twotino: 1996 TR₆₆ | 1998 SM₁₆₅ | 1997 SZ₁₀ | 1999 RB₂₁₆ | 2000 JG₈₁

Scattered disk object: 1995 TL₈ | 1996 GQ₂₁ | 1996 TL₆₆ | 2000 OO₆₇ | 2000 OM₆₇ | 2001 KC₇₇ | 2001 UR₁₆₃ | 2002 CY₂₂₄ | 2002 GX₃₂ | 2003 UB₃₁₃**

Unclassified Objects : 1994 JS | 1994 JR₁ | 1995 DA₂ | 1995 SM₅₅ | 1996 TQ₆₆ | 1997 CR₂₉ | 1997 CS₂₉ | 1997 CU₂₉ | 1997 QJ₄ | 1998 HJ₁₅₁ | 1998 HK₁₅₁ | 1998 HP₁₅₁ | 1998 HM₁₅₁ | 1998 KR₆₅ | 1998 SM₁₆₅ | 1998 SN₁₆₅1998 US₄₃ | 1998 VG₄₄ | 1998 WW₂₄ | 1998 WA₃₁ | 1998 WU₃₁ | 1998 WW₃₁ | 1998 WA₂₅ | 1999 CP₁₃₃ | 1999 CL₁₅₈ | 1999 CC₁₅₈ | 1999 DF₉ | 1999 HT₁₁ | 1999 HB₁₂ | 1999 HC₁₂ | 1999 KR₁₆ | 1999 OY₃

Natural satellites : Charon (Pluto) | Hydra (Pluto) | Nix (Pluto) | S/2000 (1998 WW₃₁) 1 | S/2005 (2003 EL₆₁) 1 | S/2005 (2003 EL₆₁) 2 | S/2005 (2003 UB₃₁₃) 1 |}

Large trans-Neptunian objects[http://encycl.opentopia.com/ edit ]

Kuiper belt: Pluto (Charon) | Orcus | Ixion | 2002 UX25 | Varuna | 2002 TX300 | 2003 EL61 | Quaoar | 2005 FY9 | 2002 AW197

Scattered disc: 2002 TC302 | 2003 UB313 | 2004 XR190 | Sedna†

See also Triton, astronomical objects and the solar system's list of objects, sorted by radius or mass.  For pronunciation, see: Centaur and TNO pronunciation. † Current MPC classification. Some consider Sedna an Oort cloud object.

 

---

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.

---

Search Titles

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

?

E-mail this article to:

Personal Message: