Pluto's moon no longer an only child
The tiny, distant and frozen planet Pluto, for 30 years believed to
have just one moon, has suddenly been found to have two more
satellites.
Only discovered in 1930 because of its vast distance from Earth,
Pluto has remained a largely enigmatic object ever since.
Some 3 billion miles from the sun, Pluto, the ninth planet, is the
only one not yet to have been visited by a spacecraft.
Its first known satellite, Charon, was not discovered until 1978.
With a diameter of over 745 miles, it is half that of
Pluto--abnormally large for a moon in relation to its
primary.
But now, using images from the Hubble Space Telescope, scientists
from Johns Hopkins University, Southwest Research Institute and the
Massachussetts Institute of Technology say they have found two more
tiny orbiting satellites, P1 and P2.
Both are traveling outside the orbit of Charon and are tiny by
comparison, the scientists wrote in the journal Nature.
P1, the more distant of the two from Pluto, has a diameter of
between 37 and 102 miles, while P2 is 20 percent smaller.
"Although definitive orbits cannot be derived, both new satellites
appear to be moving in circular orbits in the same orbital plane as
Charon with orbital periods of about 38 days for P1 and 25 days for
P2," they wrote.
The discovery of the two new members of Pluto's family make it the
only object in the Kuiper Belt--a vast region of rock and ice
beyond Neptune which contains debris from the formation of the
solar system--known to have multiple satellites, the scientists
said.
