Voyagers 1 and 2, following in the "footsteps" of Pioneers 10 and 11, were launched from Kennedy Space Center in 1977. Their missions were to fly past Jupiter and Saturn, relaying information on the planets and their environments to Earth. They're still alive, monitoring the conditions in the farthest reaches of the solar system. Voyager 1, 64 astronomical units (Earth-Sun distances) from Sun, and Voyager 2, nearly 50 astronomical units away (Compare with Pluto's 39.5.), are now on an interstellar mission to learn more about the regions of space in and beyond which our star has a significant influence.
Voyager 2 was launched on Aug. 20, 1977, and sixteen days later, on Sept. 5, Voyager 1 was launched on a different, faster trajectory that resulted in its passing Voyager 2 and reaching Jupiter in March, 1979, four months before Voyager 2. Voyager 1 continued ahead of Voyager 2, arriving at Saturn in November, 1980. Gravity boosts by Jupiter had pitched Voyager 1 on toward Saturn, and a gravity boost by Saturn threw Voyager 1 out of the plane of the solar system, south of Earth's orbital plane, the ecliptic.
Voyager 2 also received gravity boosts from Jupiter in July, 1979, and from Saturn in August, 1981. Scientists took advantage of an approximate line-up of Jupiter, Saturn, Uranus and Neptune, all on the same side of Sun, to have Saturn's boost relay the space probe on toward Uranus, which it passed in January, 1986. A boost from Uranus then forwarded Voyager 2 on to Neptune. It arrived at Neptune in December, 1989, where a gravity assist by Neptune propelled Voyager 2 out of the solar system north of the ecliptic.
The two Voyagers carried TV cameras and other instruments that made numerous discoveries and provided much information that scientists have been digesting as they seek a better understanding of these gas giants, of interplanetary space, and of the structure of the solar system. These discoveries have also raised questions that scientists must address as they seek to expand our understanding of Sun's family.
Sun's region of space, called the heliosphere, is characterized by the presence of the solar wind, particles ejected from Sun's corona that move outward at supersonic speeds under the influence of Sun's magnetic field. Scientists believe that the heliosphere's end will be detected in the slowing of solar wind particles as they encounter a "galactic wind" associated with the large scale structure of the Milky Way. It is possible that Voyager 1 will reach the end of Sun's sphere of dominance in another 4 or 5 years, more than 80 astronomical units from Sun. The Voyagers will spend several years passing through this transition zone and will emerge into interstellar space still capable of making measurements of the properties of their surroundings.
Nuclear generators supply electrical power for the instruments and radios on the two Voyagers as they recede from the solar system at rates of more than 3 astronomical units per year. Careful monitoring of the power supplies will enable the scientists to reduce power demands by selectively turning off instruments and conserving the electrical power for the most critical measurements and their transmission to Earth. The two Voyagers are expected to return information until at least 2020.
Learn more about the discoveries of Voyagers 1 and 2 at our solar system's gas giant planets by viewing "The Voyager Encounters," narrated by Patrick Stewart, at the Department of Physics' Tomchin Planetarium in 425 Hodges Hall. Presentations of this sky show are made on the second and fourth Fridays of each month at 7, 8, and 9 p.m. Because seating is limited, free reservations must be made by calling 293-3422, ext. 1443, between 8:30 a.m. and 4:00 p.m. on weekdays. If skies are clear, Tomchin Observatory is also open following the shows.