On July 4, the Juno spacecraft arrived at Jupiter. It had just completed a 5-year trek across some 2.8 billion kilometers (1.74 million miles) of space. It quickly entered orbit about the planet. The tiny spacecraft survived its first encounter with Jupiter’s intense radiation. Proof came when its camera sent back this panoramic snapshot on July 10. It shows Jupiter (left) with its great red spot and three of the gas giant’s four biggest moons. At the time this photo was made, the craft was 4.3 million kilometers (2.7 million miles) from the planet. Now Juno is swinging out away from the planet. It’s on the outbound leg of its first 53.5-day orbit of Jupiter. It won’t get close enough for true high-resolution images until August 27. But this postcard confirms that the spacecraft is ready to begin its real work. That will be sending back photos and other data to help astronomers better understand our solar system’s biggest planet.
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astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
gas giant A giant planet that is made mostly of the gases helium and hydrogen. Jupiter and Saturn are gas giants.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
orbit The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
solar system The eight major planets and their moons in orbit around the sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
C. Crockett. “Wandering Jupiter could have swept inner solar system clean.” Science News. Vol. 189, April 2, 2016, p. 7.
Mission Juno webpage. Southwest Research Institute.
Jupiter fact sheet. NASA. Updated May 16, 2016.