Lunar Abundance
Not so long ago, people were getting all excited about whether there might be a new planet for the solar system*, and now it seems that there are to be a new moon or two for Pluto. A NASA press release# (which has accompanying photographs showing the moons) describes things this way:
Pluto was discovered in 1930. The planet resides 3 billion miles from the sun in the heart of the Kuiper Belt, a vast region of icy, rocky bodies beyond Neptune's orbit. In 1978, astronomers discovered Charon, Pluto's only confirmed moon.
"If, as our new Hubble images indicate, Pluto has not one, but two or three moons, it will become the first body in the Kuiper Belt known to have more than one satellite," said Hal Weaver of the Johns Hopkins Applied Physics Laboratory, Laurel, Md. He is co-leader of the team that made the discovery.
The candidate moons, provisionally designated S/2005 P1 and S/2005 P2, are approximately 27,000 miles (44,000 kilometers) away from Pluto–in other words, two to three times as far from Pluto as Charon.
The moons are thought to be between "64 and 200 kilometers" in diameter, which is pretty small, about 1/15th to 1/20th the diameter of Earth's moon. Pluto itself has only 65% of our moon's diameter.
The discovery was made using the Hubble Space Telesecope by a team of scientists from the Johns Hopkins University Applied Physics Lab (in Laurel, Maryland), the Lowell Observatory (Flagstaff, Arizona), and the Southwest Research Institute (Boulder, Colorado).
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*And showing their excitement, therefore, by arguing about what a "planet" really is.
#"New Moons of Pluto: Astronomers may have found two new moons orbiting Pluto.", 1 November 2005.
In: All, Curious Stuff, It's Only Rocket Science