Hubble discovers new Pluto moon

The powerful Hubble telescope has spotted a fourth moon orbiting Pluto, announces NASA.

ASTRONOMERS USING NASA'S POWERFUL Hubble Space Telescope have spotted a tiny fourth moon around Pluto, the smallest ever glimpsed around the icy dwarf planet.

The small moon, named P4 for now until a better name is decided upon, is only about 13km to 24km in diameter.

"I find it remarkable that Hubble's cameras enabled us to see such a tiny object so clearly from a distance of more than (five billion kilometres)," said lead observer Mark Showalter of the SETI Institute in Mountain View, California.

Pluto's largest moon, Charon, is 1043km across. The other two, Nix and Hydra, are between 32km and 113km in diameter, NASA said. Hubble discovered Nix and Hydra in 2005. Astronomers at the US Naval Observatory glimpsed Charon in 1978.

The first photo of P4 was taken with Hubble's Wide Field Camera 3 on June 28, and was confirmed by more Hubble snapshots on July 3 and July 18.

Faint smudge clarified

"The moon was not seen in earlier Hubble images because the exposure times were shorter. There is a chance it appeared as a very faint smudge in 2006 images, but was overlooked because it was obscured," NASA said.

Hubble is a potent space telescope that has transformed the field of astronomy since it was first launched in 1990.

Pluto, once known as the ninth planet from the Sun, was declassified as a full-fledged planet in August 2006 and joined the new category, dwarf planet. At about 2300km wide, it is about two-thirds the size of the moon and has a mass less than one per cent of the Earth's.

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