dipper@utastro.UUCP (Debbie Byrd) (01/14/85)
Comet Halley today is closer to the sun than the planet Jupiter. More -- in a moment. January 14 Jupiter and Comet Halley The planet Jupiter is gigantic -- with gravity so powerful that it can change the orbit of a comet. It can greatly shorten a comet's journey around the sun -- so that the comet returns on the order of tens of years -- instead of hundreds of thousands. It's not known for sure if Jupiter changed the orbit of Comet Halley -- but Halley now shows up regularly once in a typical human lifespan. About every seventy-six years, Comet Halley loops close to the sun -- then travels back out to the far reaches of the solar system. It so happens that Jupiter and Comet Halley are now nearly the same distance from the sun -- though the two bodies are nowhere near each other in space. Jupiter's average distance from the sun is five point two astronomical units -- around four hundred and eighty million miles -- or more than five times the Earth's distance from the sun. On Tuesday, Comet Halley is five point one five astronomical units from the sun -- slightly closer than Jupiter. What's more, Jupiter today is on the far side of the sun from Earth -- exactly opposite us in the solar system. If you could look down from above the north pole of the sun -- you'd see Jupiter, the sun and the Earth in a straight line today. Comet Halley doesn't quite fit into this line-up -- for one thing, it's traveling below the plane of the solar system right now. But the comet is roughly on the same side of the sun as our planet -- and more than five times farther out. Script by Diana Hadley and Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin