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Wednesday, January 18, 2006
The Outermost Planet is Not Pluto
As NASA tries again today to launch a probe to that distant world, you'll see and hear reports that say things like "the solar system's last unexplored planet." Sorry, but what we learned in elementary school is no longer true. In 2003, astronomers found another icy world that's bigger than Pluto and even farther from the sun. So either there's at least one more unexplored planet, or neither should be called a planet at all, as some astronomers contend. The official name hasn't been chosen yet for 2003 UB313, as it's technically designated. You may heard it called Xena, a nickname mentioned by its discoverers with a wink to the warrior princess of TV fame. But the co-discoverers have submitted another name, as Mike Brown's Web page makes clear. d. Because almost all the names of Greek and Roman gods have been taken by planets and asteroids, the undisclosed proposed name harkens to another tradition. By the way, last fall, the Hubble telescope discovered two more moons that orbit Pluto -- as well as one that orbits UB313. This afternoon's launch window is 1:15 to 3:15. You can watch at NASA's Web site.
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