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Hubble Confirms Plutos New Moons

Astronomers using NASA's Hubble Space Telescope have confirmed the presence of two new moons around the distant planet Pluto. The moons were first discovered by Hubble in May 2005, but the Pluto Companion Search team probed even deeper into the Pluto system with Hubble on Feb. 15 to look for additional satellites and to characterize the orbits of the moons. In the image, Pluto is in the center and Charon is just below it. The moons, provisionally designated S/2005 P 1 and S/2005 P 2, are located to the right of Pluto and Charon.
by Staff Writers
Laurel MD (SPX) Feb 22, 2006
New images by the Hubble Space Telescope confirm the discovery that Pluto has two tiny moons in addition to its larger moon Charon. Reporting in the Feb. 23 issue of the British journal Nature, a team led by Hal Weaver of the Johns Hopkins University Applied Physics Laboratory said the finding - made with the Hubble's Advanced Camera for Surveys - makes the ninth planet the first Kuiper Belt object known to have multiple satellites.

In a companion paper, discovery team members led by Alan Stern of the Southwest Research Institute in Boulder, Colo., conclude that the two small moons very likely were created by the same giant impact that gave birth to Charon. They also argue that other large binary Kuiper Belt objects have small moons accompanying them, and that Pluto's small moons may even generate debris rings that orbit the planet.

"We used Hubble's exceptional resolution to peer close to Pluto and pick out two small moons that had eluded detection for more than 75 years," said Weaver, who also serves as project scientist for NASA's New Horizons mission, which launched Jan. 19 on a nine-year journey to the Pluto system.

The satellites are easy to spot in the new Hubble images, the Weaver team writes. "That was somewhat surprising, because ground-based observers had been trying for more than a decade to find new satellites around Pluto," said Max Mutchler, from the Space Telescope Science Institute in Baltimore, which operates the orbiting telescope.

Mutchler, who was the first scientist to see the new moons when Hubble returned the images in May 2005, explained that he "felt almost certain, even when I first saw them, that they were real objects - not any sort of artifact - and that they were exhibiting orbital motion around Pluto."

That orbital motion - inferred from the different locations of the moons in pictures taken between May 15 and May 18 - is what persuaded scientists they were indeed looking at moons and not stray light, cosmic rays or other Kuiper Belt objects that happened to be passing by.

"If we assumed the orbits were circular and in the same orbit plane as Charon, we could predict the exact positions of the objects on the second day," said William Merline, an SWRI team member. "When the objects on the second day appeared almost exactly where we predicted, we were convinced - no two artifacts could follow the rules of orbital physics that 'real' objects must obey."

Stern said the similarity of the orbits of the new moons with Charon's "sheds light on the formation and evolution of the Pluto system, as well as on the process by which satellites are formed in the Kuiper Belt."

The belt is a band of icy, rocky objects and dwarf planets that orbit the Sun in the outer region of our solar system, beyond the orbit of Neptune. It has been known since 1992, and Pluto is its most prominent member.

Charon was discovered in 1978, nearly half a century after Pluto's discovery in 1930. With diameters estimated to lie between 35 and 100 miles, the new moons, provisionally designated S/2005 P1 and S/2005 P2, are roughly 10 times smaller than Charon. They also are about 600 times fainter than Charon, 4,000 times fainter than Pluto, and are hidden in the glare of nearby Pluto and Charon when viewed by ground-based optical telescopes. The researchers said this is the reason the moons evaded detection before Hubble looked for them.

Weaver said the Long Range Reconnaissance Imager, or LORRI, telescopic camera on the New Horizons spacecraft should be able to probe the new moons and resolve surface features down to 600 yards. These observations would add to the primary mission science plans to characterize the global geology of Pluto and Charon, map their surface compositions and temperatures, and examine Pluto's atmospheric composition and structure. New Horizons also will map the two smaller satellites in color and black-and white, and map their surface compositions and temperatures.

"We're getting four fascinating targets for the price of two," Weaver said. "The opportunity to explore the 'bookends' of Kuiper Belt object size distribution, with Pluto and Charon at one end and P1 and P2 at the other, is an unexpected treat."

Hubble is scheduled to take another set of Pluto images in early March.

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JAXA Akari Space Telescope In Orbit
Uchinoura Space Center Japan (SPX) Feb 22, 2006
JAXA has confirmed through telemetry that the Akari infrared space telescope has deployed its solar array paddle successfully. The spacecraft, which was launched at 6:28 a.m. local time Wednesday aboard an M-V-8 rocket, originally was named ASTRO-F, but mission controllers renamed it Akari, meaning a "light," as soon as it entered orbit.

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