Jupiter

"Next Monday, I am likely to develop a cough, owing to the unlucky conjunction of Mars and Jupiter. You know her - just put in loads of misery, she'll lap it up."

- Ron Weasley working on his Divination homework with Harry

Jupiter is the fifth planet from the sun and the largest within the solar system.

Moons
"Harry, yours is okay except for this bit at the end, I think you must have misheard Professor Sinistra. Europa's covered in ice, not mice — Harry?"

- Hermione Granger correcting an Astronomy essay by Harry Potter in 1995

Jupiter has several large moons that human astronomers have studied and mapped. The largest, in order from innermost to outermost orbit around the planet, are:


 * Io — Noted for the unique presence of volcanoes.
 * Europa — Noted for its ice-covered surface.
 * Ganymede — Noted for being the largest of all Jupiter's moons.
 * Callisto

Students at Hogwarts School of Witchcraft and Wizardry learned about Jupiter's moons in Astronomy class. They begun with learning the moons' names in their first year, then progressed to in-depth study of them in their fifth year, drawing pictures of them and writing long essays about their unique features.

History
In 1992, while Harry Potter, Ron Weasley, and Hermione Granger were preparing for their final exam in Astronomy in the Hogwarts library, Harry studied a map of Jupiter to learn the names of its moons.

After fleeing into the woods to escape the Death Eaters' attack on the 1994 Quidditch World Cup campsite, Harry, Ron, and Hermione came upon clearing filled with Veela. Ron fell under the influence of their charming powers and claimed to have invented a broomstick capable of reaching Jupiter in an effort to impress them.

In 1994, Ron Weasley became frustrated with a Divination assignment that required him to produce an astrological forecast of the upcoming month, and decided to simply make things up. He wrote that he would be likely to develop a cough the following Monday due to an "unlucky conjunction of Mars and Jupiter" because he thought Professor Trelawney would "lap it up" if he "put in loads of misery."

Professor Sinistra assigned her fifth-year Astronomy students an essay on Jupiter's moons in 1995. Hermione read over and corrected her friends' essays, finding that Ron had mistakenly written that Callisto was Jupiter's largest moon and that Io wasn't the one with volcanoes, and that Harry's essay claimed Europa was covered in mice, rather than ice. After sitting his Astronomy O.W.L. theory exam later that term, Harry wasn't sure he had correctly named all of Jupiter's moons, but he felt certain that he hadn't claimed there were mice living on any of them.

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Philosopher's Stone (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix