dipper@utastro.UUCP (Debbie Byrd) (10/14/86)
Jupiter and the Trojan Asteroids -- when we come back. October 14 Trojan Asteroids Gravity works in a variety of ways in our solar system. It lets planets orbit the sun, and moons orbit planets -- and more. For example, in 1772, a French mathematician predicted that two large bodies in orbit around each other should create two other places where smaller bodies can get gravitationally "stuck." According to Joseph Lagrange, smaller bodies will move through space with the two larger ones -- never getting much closer to or farther from either of them. These special places -- where small objects in space are gravitationally balanced with two large objects -- are now called Lagrangian points. More than a century after Lagrange's prediction, an unusually dark asteroid was sighted moving in the orbit of Jupiter -- at the Lagrangian point in front of Jupiter. Just as Lagrange had predicted, the asteroid, the sun, and Jupiter all remain about 500 million miles apart -- forming a triangle with sides of equal length. Soon more asteroids were found around that Lagrangian point -- and near the second Lagrangian point -- also in Jupiter's orbit -- 500 million miles behind the giant planet. Both groups of asteroids became known as the Trojan Asteroids. The largest ones moving in front of Jupiter were named for Greek heroes of the Trojan War -- and those following Jupiter for the defenders of Troy. There are two exceptions, however -- each group has one asteroid named for an enemy prisoner. There are dozens of Trojan asteroids -- with perhaps three and a half times as many moving in front of Jupiter as moving behind. Why that is, no one knows. It's another of the many puzzles in the solar system remaining to be solved. Script by Bill Edrington. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin