Long-Shot Jackpot : Voyager 2 Finds Six Additional Moons Orbiting Uranus

The Voyager 2 spacecraft, streaking toward its encounter with Uranus next Friday morning, has discovered six additional moons orbiting the distant planet, scientists at the Jet Propulsion Laboratory announced Thursday.

The discovery of the small moons, ranging in size from 20 to 30 miles in diameter, doubles the number of known satellites orbiting the planet. And many additional moons are expected to be discovered as scientists prepare to devour images sent back by the spacecraft in the next few days.

Uranus, the seventh planet from the sun, is so far away and so dimly lighted that little is known about it.

Prior to Voyager, only five moons had been detected. But images that Voyager sent back in December revealed a sixth moon, announced earlier this month. All seven moons discovered by the craft, launched in 1977, are much smaller than those that had been previously identified.

Thursday’s announcement comes amid mounting excitement because by late next week, Voyager 2 is expected to begin sending back more information about Uranus than astronomers have been able to glean in more than 200 years.

All the newly discovered moons are in orbits between the outermost of the planet’s nine known rings and the moon Miranda, and they are in orbits ranging from 38,370 miles to 46,700 miles from the planet’s center.

None of the moons is in an area that would endanger Voyager, because they are some distance from the course the craft will follow, according to Brad Smith, chief of the Voyager imaging team.

He said the six new moons “are sprinkled throughout the area between the rings and Miranda.” And although they are in similar orbits, he said it is impossible to tell “whether they are small pieces of debris from the formation of the Uranian system or fragments from larger bodies that suffered devastating collisions.”

No photos have been released of the new moons because the spacecraft is still so far away from Uranus that the satellites appear only as tiny specks of light.

Voyager 2 is to dart through the heart of the Uranian system Friday at about 45,000 miles an hour, passing within about 18,000 miles of Miranda and about 66,000 miles of the cloud tops that enshroud the planet. That will give scientists their first close look at Uranus and its moons and mysterious dark rings; but even then they will have to wait awhile for the data.

Uranus is so far away that it will take 2 hours and 42 minutes for data traveling at the speed of light to reach the Earth.

This will not be the first time Voyager 2 has been on center stage. It sent back spectacular photographs from Jupiter and Saturn when it visited those planets along with a sister ship, Voyager 1, in 1979 and 1981. And the durable little spacecraft’s long odyssey is far from over. In 1989, it is expected to return similar pictures from Neptune, the eighth planet, before leaving the solar system.

Center for Media

Next week, JPL will become a mecca for the media, with more than 250 reporters from around the world descending on the Pasadena facility.

“And that doesn’t even include members of TV crews,” a JPL official said.

Although the flyby occurs next Friday, it will probably be a day or two before photos can be prepared and released, and information will continue to flow for several days.

During the close encounter with Uranus, which should last a little more than four hours, Voyager will take a series of photographs, and it will use 11 sensors to learn more about the planet’s atmosphere, composition, magnetic field and peculiar orientation in the solar system.

Unlike the other planets, Uranus appears to have been tipped over on its side, and it is now pointing its south pole at the sun.

Deflected Outward

Voyager’s course will carry it just inside the orbit of Miranda so that it can use gravitational deflection to send it out toward its next encounter. A successful tour of Neptune would leave only Pluto unvisited by a mission from planet Earth.

Identified by Numbers

The new moons discovered at Uranus were found by members of the Voyager imaging team who have been studying pictures Voyager sent back on three separate days earlier this month. Until they are given formal names, the new moons are identified only by numbers--1986U1 through 1986U6.