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What Is Juno?
December 27, 2011

Juno is a NASA spacecraft that is going to Jupiter. Juno launched in 2011 and will arrive at Jupiter in 2016.

The spacecraft's name comes from Roman mythology. According to the myth, the god Jupiter would hide behind clouds. But his wife, the goddess Juno, could see through them. As in the story, the planet Jupiter is covered with clouds. The spacecraft Juno will help NASA learn about what the planet Jupiter is like behind the clouds.

How Will Juno Study Jupiter?
The Juno spacecraft launched aboard an Atlas V (Roman numeral 5) rocket on Aug. 5, 2011. It will reach Jupiter in 2016. The spacecraft will orbit Jupiter 32 times, coming within 3,000 miles (4,800 kilometers) above the tops of the planet's clouds. Juno will orbit closer to Jupiter than any spacecraft has before. It will orbit around Jupiter's poles for about one year.

Science instruments on board Juno will study Jupiter's atmosphere. They will use Jupiter's magnetic field, gravity field and naturally occurring radio waves to study the mysterious interior of the giant planet. Juno also will take the first pictures of Jupiter's polar regions and study the huge aurora that lights up Jupiter's north and south poles.

Juno will measure the amount of water and ammonia in Jupiter's atmosphere to help learn how giant planets formed. By making maps of Jupiter's gravitation and magnetic fields, Juno can determine the mass of Jupiter's core. Juno will learn about Jupiter's atmosphere under the clouds to understand Jupiter's structure. And Juno will sample the electrons and ions in Jupiter's magnetosphere to understand why the planet has the brightest auroras in the solar system.
Juno has three very large solar panels. The solar panels extend outward from Juno's six-sided body. The solar arrays measure approximately 2.65 meters wide by 8.9 meters long (about 9 feet wide by 29 feet long). The spacecraft and solar wings together span more than 20 meters (66 feet). Once in orbit, the three arrays will generate about 450 watts of electricity, which is about the same amount of electricity it takes to operate a computer.

Why Is NASA Studying Jupiter?
The goal of the Juno mission is to help scientists better understand the origin and evolution of Jupiter and how planets form. NASA is always trying to understand the world around us - Earth, the solar system and the universe beyond. Jupiter is a type of planet called a "gas giant." Like the sun, Jupiter does not have a solid surface and is mostly hydrogen and helium. By knowing that Jupiter is made of these gases, NASA knows that Jupiter must be formed from the sun's leftovers. Because Jupiter is so massive, it still has its original composition and has not changed as much over time as the smaller planets. By studying Jupiter's composition, NASA can better understand the history and composition of the solar system. With its more than 60 moons in orbit, Jupiter is like a star in a mini solar system. NASA not only can learn more about our solar system, but also the planetary systems around distance stars. Hidden beneath Jupiter's clouds dense clouds are the mysteries of the solar system that NASA and Juno hope to uncover.

Words to Know:
origin: basic source or cause
evolution: a process of change in a certain direction; especially a process of constant change from a lower or simple state to a higher or complex state
aurora: a natural display of light in the sky
ion: an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons
magnetosphere: the region surrounding a planet where the magnetic field is located

More About Juno and Jupiter:
› Movie Trailer: "Conquering the Gas Giant"
› Mission Juno Video   →
› Juno Mission
› What Is Jupiter?
› JunoQuest   →
› Latest Juno Spacecraft Images

Read What Is Juno? Grades K-4

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Heather R. Smith/NASA Educational Technology Services
Denise Miller/NASA Educational Technology Services

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An artist's drawing of the Juno spacecraft flying in front of Jupiter
NASA's Juno mission will study Jupiter, the largest planet in the solar system.
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Ultraviolet view of the auroras at Jupiter's north and south poles
Juno will study the bright auroras at Jupiter's poles.
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Page Last Updated: September 13th, 2013
Page Editor: NASA Administrator