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Yet Another Tenth Planet Discovery (!)
Found via Jeff Foust's Space Today, which is probably a good place to go for updates.After 75 years of speculation and false leads, it finally seems to have happened. A team of astronomers using the 48-inch Samuel Oschin Telescope at Palomar Observatory and the 8-meter Gemini North telescope on Mauna Kea, Hawaii, has discovered the largest Kuiper Belt object (KBO) ever. It is bigger than Pluto, the 9th planet. The object, designated 2003 UB313, is currently 97 astronomical units (Earth-Sun distances) away â more than twice Pluto's average distance from the Sun. It is a scattered-disk object, meaning that at some point in its history Neptune likely flung it into its highly inclined (44°) orbit. It's currently glowing at magnitude 18.9 in the constellation Cetus. Discoverers Michael E. Brown (Caltech), Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University) first imaged the object on October 21, 2003, but didn't see it move in the sky until reimaging the same area 15 months later on January 8, 2005. "We tried looking at it with the Spitzer Space Telescope and didn't detect it. So we have an upper limit on the size. It can't be any more than 3,000 kilometers across," says Brown. But the lower limit derived from its brightness â even by assuming its surface is 100 percent reflective â still makes it larger than Pluto, which is 2,250 km (1,400 miles) across... And Yet Another Big KBO And on the planet discovery reported Friday AM: A second big Kuiper Belt discovery also made news today: 2003 EL61. That body, located about 52 a.u. away, was discovered by Brown and his team and was also reported by astronomers at the Sierra Nevada Observatory in Spain. It appears to be the third-largest Kuiper Belt object known to date, with about 70 percent of Pluto's diameter â bested only by Pluto itself and 2003 UB313. Moreover, by a great stroke of luck, 2003 EL61 has a tiny satellite revolving around it, at an apparent distance of about 1.5 arcseconds. According to Brown's group, the satellite completes an orbit every 49 days in a nearly circular orbit some 49,500 km (30,760 miles) from the main body. The satellite's orbit has allowed the team to determine the mass of 2003 EL61: about a quarter that of Pluto. Brown and his team have also looked at 2003 EL61 with the Spitzer Space Telescope. Those observations are still being analyzed, but, Brown notes, "The spectra are dominated by water ice. It looks much like [Pluto's moon] Charon." Well, at least it's made out of different stuff than Sedna. They still haven't figured it out. It's probably an isomer of Illudium Phosdex unknown to earth science. Posted by: Phil Fraering 2005-07-30 |
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