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Mon Jan 13, 5:32 PM ET |
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WASHINGTON (Reuters) - Astronomers have found three previously unknown moons around Neptune, bringing the total for the distant giant planet to 11, the Harvard-Smithsonian Center for Astrophysics reported on Monday.
These moons are the first to be discovered around Neptune since the NASA (news - web sites) Voyager II flyby in 1989, and the first discovered with a ground-based telescope since 1949, the center said in a statement.
The three new moons were difficult to detect, since they are only about 18 to 24 miles in diameter and their distance from the sun means they are about 100 million times fainter than anything that can be seen with unaided eyes from Earth.
Using the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile and the Canada-France-Hawaii Telescope in Hawaii, the international team of astronomers took multiple exposures of the sky around Neptune. The new moons showed up as points of light.
Before this, Neptune was known to have eight moons. The two largest -- Triton, discovered in 1846, and Nereid, discovered in 1949 -- are also the irregular ones. Triton orbits in a direction opposite to the planet's rotation, and Nereid's orbit is highly elliptical.
The six regular satellites were discovered by the Voyager probe during its encounter with Neptune. The three new satellites were missed by Voyager II because of their faintness and great distance from Neptune, the statement said.
An image of one of the three new Neptunian moons is online at http://cfa-www.harvard.edu/press/pr0303_image.html.
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