Free Republic

Odd orbits of remote objects hint at unseen world, new calculations suggest. An as yet undiscovered planet might be orbiting at the dark fringes of the solar system, according to new research.Too far out to be easily spotted by telescopes, the potential unseen planet appears to be making its presence felt by disturbing the orbits of so-called Kuiper belt objects, said Rodney Gomes, an astronomer at the National Observatory of Brazil in Rio de Janeiro. Kuiper belt objects are small icy bodies—including some dwarf planets—that lie beyond the orbit of Neptune. Once considered the ninth planet in our system, the...

Are comets born in great swarms? The puzzling abundance of comets in short solar orbits has led a pair of astronomers to suggest that they are fragments of larger bodies that crumbled as they entered the inner solar system. Short-period comets take less than 200 years to circle the sun and are thought to originate in the Kuiper belt of icy objects beyond Neptune. Some Kuiper-belt objects (KBOs) are in vulnerable orbits that allow the gravity of the outer planets to tug them inwards, where the sun's heat turns them into comets. However, there seem to be too few KBOs...