dipper@utastro.UUCP (Debbie Byrd) (03/03/86)
Pioneer 10 was the first spacecraft to venture into the outer solar system. More -- coming up. March 3 Pioneer 10 On today's date in the year 1972, NASA's Pioneer 10 spacecraft was launched toward the outer solar system. It was to become the first craft to travel beyond the asteroid belt -- and the first to encounter mighty Jupiter. Pioneer 10 is now on its way out of the solar system. It is now farther from the sun than any of the known planets -- still sampling the environment through which it moves -- and still transmitting data back to Earth. The spacecraft was originally designed for a mission lasting 21 months. Its primary mission was to encounter Jupiter. But the spacecraft has done much more. Scientists used Pioneer 10 data to go beyond the previous picture of the solar system -- that of a central sun surrounded by a flat disk of planets. Thanks to Pioneer 10, we can now envision a huge magnetic bubble containing the planets and sun -- a bubble that may be streamlined into a teardrop as the sun at its heart moves through the galaxy. Some scientists also think this bubble "breathes" -- expands and contracts -- with each 11-year cycle of activity on the sun. The outer boundary of the bubble is known as the heliopause, the end of the sun's influence. Outside the heliopause lies the unsampled gas and dust of interstellar space. Although no one knows exactly when it will happen, Pioneer 10 will be the first craft from Earth to cross the heliopause -- and venture into the galaxy at large. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin