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Pluto has three moons. They are Charon, Nix and Hydra. Charon is the largest
moon.
Moons: Nix
and Hydra
Two new moons of Pluto were first spotted in May 2005 Hubble Space Telescope
images, then confirmed in archival Hubble pictures taken in June 2002.
The moons were provisionally
designated S/2005 P 1 (Hydra) and S/2005 P 2 (Nix).
On
June 21, 2006 the International Astronomical Union (IAU) announced
the formal names for Pluto's two discovered small moons: Nix and Hydra. The IAU
chose the name to complement Pluto, who was the Greco-Roman god of the
underworld. Nix represents the Greek goddess of night and Hydra is the
nine-headed monster that guarded Lake Lerna, an entrance to the underworld in
Greek mythology. Nix's off-spring Charon, who ferried souls not the underworld,
lent his name to Pluto's largest moon, which was discovered in 1978.
The correct spelling of Nix is actually Nyx, but as an asteroid had already been
given that name, the IAU accepted the alternative spelling.
Charon Moon
 Charon
Moon was discovered in 1978. Its diameter is 1212 km (753
miles) which is more than half as wide in size as Pluto and the Pluto-Charon
system is like a double planet. Charon orbits Pluto every 6.4 days and has a
synchronous orbit (the pair show the same face to each other all the time). To
an observer on the planet, Charon appears to be stationary in the sky like a
geostationary satellite orbiting the Earth.
Pluto and Charon have been called a double planet because Charon is larger
compared to Pluto
Hydra
Hydra is the outer-most natural satellite of Pluto. It was
named after Hydra, the monster who guarded the waters of Pluto / Hades's
underworld in Greco-Roman Mythology. The name Hydra was announced on June 21,
2006, in IAU Circular 8723, along with the formal designation Pluto III. Hydra
is to be visited along with Pluto by the New Horizons mission in 2015.
At the time of discovery, Hydra was about 25 percent brighter than its sister
moon Nix, which led to the assumption that its diameter was some 10 percent
larger. However, in subsequent observations the two moons were about equal in
brightness. This is likely due to an oblong shape, although brightness variation
over its surface may also be responsible. Hydra appears to be spectrally neutral
like Charon and probably Nix, but unlike Pluto, which is reddish.
Although its size has not been directly measured, calculations based on its
brightness give it a diameter of between 40 km, if its reflectivity is similar
to Charon's 35 percent, and about 130 km, if it has a reflectivity of 4 percent
like the darkest Kuiper belt objects (KBOs).
Did you know?
In 2006 Planet Pluto was controversially reclassified as a Dwarf Planet.
Books
Pluto and Charon : Ice Worlds on the Ragged Edge of the Solar
System by Alan Stern, Jacqueline Mitton
From Amazon.com,
Amazon.co.uk
Pluto: The Ninth Planet by Michael D.
Cole
From Amazon.com,
Amazon.co.uk
Beyond Pluto by John Davies (Author)
From Amazon.com,
Amazon.co.uk
Moons of Pluto Links:
Picture: The artist's concept above shows the Pluto
system from the surface of one of the moons. The other members of
the Pluto system are just above the moon's surface. Pluto is the
large disk at center, right. Charon is the smaller disk to the
right of Pluto. The other moon is the bright dot on Pluto's far
left. Credit: NASA, ESA and G. Bacon (STScI)
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