On September 5, 1977, NASA launched the Voyager I spacecraft. Nearly 40 years later, the phenomenally successful Voyager I and its sister spacecraft, Voyager II (which actually launched earlier), continue to return data and receive commands.The primary mission of the Voyager program was to explore the planets Jupiter and Saturn, as well as their moon and ring systems. Voyager II went on to explore our solar system’s other gas giants, Uranus and Neptune. As of 2014, it is still the only spacecraft to have flown by those planets.Voyager I has traveled more than 19.1 billion kilometers (11.9 billion miles) from Earth—the farthest of any spacecraft. Voyager I has actually left our solar system and is now traveling through the interstellar medium at about 520 million kilometers (325 million miles) per year. The spacecraft is expected to transmit data until about 2025.
Term Part of Speech Definition Encyclopedic Entry asteroid Noun
irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.
celestial object made up of ice, gas, and dust that orbits the sun and leaves a tail of debris.
an order or direction.
data Plural Noun
(singular: datum) information collected during a scientific study.
gas giant Noun
one of the four enormous outermost planets in the solar system (Jupiter, Saturn, Neptune, Uranus), composed mostly of gases instead of rock. Also called a Jovian planet.
interstellar medium Noun
material in the space between star systems, mostly hydrogen plasma and cosmic dust.
to start or instigate.
important goal or purpose.
natural satellite of a planet.
Encyclopedic Entry: moon NASA Noun
(National Aeronautics and Space Administration) the U.S. space agency, whose mission statement is "To reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind."
outer space Noun
space beyond Earth's atmosphere.
large, spherical celestial body that regularly rotates around a star.
Encyclopedic Entry: planet primary Adjective
first or most important.
to get or accept.
ring system Noun
thin circles of dust, gas, and rocks that orbit a planet.
solar system Noun
the sun and the planets, asteroids, comets, and other bodies that orbit around it.
vehicle designed for travel outside Earth's atmosphere.
to pass along information or communicate.
movement from one place to another.