The Galilean moons, or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They are the most readily visible Solar System objects after the unaided visible Saturn, the dimmest of the classical planets, allowing observation with common binoculars, even under night sky conditions of high light pollution. The invention of the telescope enabled the discovery of the moons in 1610. Through this they became the first Solar System objects discovered since humans have started tracking the classical planets, and the first objects to be found to orbit a planet other than the Earth.
Callisto, or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. In the Solar System it is the third-largest moon after Ganymede and Saturn's largest moon Titan, and as large as the smallest planet Mercury, though only about a third as massive. Callisto is, with a diameter of 4821 km, roughly a third larger than the Moon and orbits Jupiter on average at a distance of 1883000 km, which is about six times further out than the Moon orbiting Earth. It is the outermost of the four large Galilean moons of Jupiter, which were discovered in 1610 with one of the first telescopes, being visible from Earth with common binoculars.
Ganymede, or Jupiter III, is the largest and most massive natural satellite of Jupiter as well as in the Solar System, being a planetary-mass moon. It is the largest Solar System object without an atmosphere, despite being the only moon in the Solar System with a substantial magnetic field. Like Titan, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io or the Moon.
"The Green Hills of Earth" is a science fiction short story by American writer Robert A. Heinlein. One of his Future History stories, the short story originally appeared in The Saturday Evening Post, and it was collected in The Green Hills of Earth. Heinlein selected the story for inclusion in the 1949 anthology My Best Science Fiction Story. "The Green Hills of Earth" is also the title of a song mentioned in several of Heinlein's novels.
Orphans of the Sky is a science fiction novel by American writer Robert A. Heinlein, consisting of two parts: "Universe" and its sequel, "Common Sense". The two novellas were first published together in book form in 1963. "Universe" was also published separately in 1951 as a 10¢ Dell paperback. The work presents one of the earliest fictional depictions of a generation ship.
The Future History is a series of stories created by Robert A. Heinlein. It describes a projected future of the human race from the middle of the 20th century through the early 23rd century. The term Future History was coined by John W. Campbell Jr. in the February 1941 issue of Astounding Science Fiction. Campbell published an early draft of Heinlein's chart of the series in the May 1941 issue.
There are 95 moons of Jupiter with confirmed orbits as of 23 October 2023. This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that were only briefly captured by telescopes. All together, Jupiter's moons form a satellite system called the Jovian system. The most massive of the moons are the four Galilean moons: Io, Europa, Ganymede, and Callisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. Much more recently, beginning in 1892, dozens of far smaller Jovian moons have been detected and have received the names of lovers or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 91 known moons and the rings together composing just 0.003% of the total orbiting mass.
Io, or Jupiter I, is the innermost and third-largest of the four Galilean moons of the planet Jupiter. Slightly larger than Earth's moon, Io is the fourth-largest moon in the Solar System, has the highest density of any moon, the strongest surface gravity of any moon, and the lowest amount of water of any known astronomical object in the Solar System. It was discovered in 1610 by Galileo Galilei and was named after the mythological character Io, a priestess of Hera who became one of Zeus's lovers.
Lucky Starr and the Moons of Jupiter is the fifth novel in the Lucky Starr series, six juvenile science fiction novels by Isaac Asimov that originally appeared under the pseudonym Paul French. The novel was first published by Doubleday & Company in August 1957. It is the only novel by Asimov set in the Jovian system.
The science fiction writer Robert A. Heinlein (1907–1988) was productive during a writing career that spanned the last 49 years of his life; the Robert A. Heinlein bibliography includes 32 novels, 59 short stories and 16 collections published during his life. Four films, two TV series, several episodes of a radio series, at least two songs and a board game derive more or less directly from his work. He wrote the screenplay for Destination Moon (1950). Heinlein also edited an anthology of other writers' science fiction short stories.
Jupiter, the largest planet in the Solar System, has appeared in works of fiction across several centuries. The way the planet has been depicted has evolved as more has become known about its composition; it was initially portrayed as being entirely solid, later as having a high-pressure atmosphere with a solid surface underneath, and finally as being entirely gaseous. It was a popular setting during the pulp era of science fiction. Life on the planet has variously been depicted as identical to humans, larger versions of humans, and non-human. Non-human life on Jupiter has been portrayed as primitive in some works and more advanced than humans in others.
The Heinlein juveniles are the science-fiction novels written by Robert A. Heinlein for Scribner's young-adult line. Each features "a young male protagonist entering the adult world of conflict, decisions, and responsibilities." Together, they tell a loosely connected story of space exploration. Scribner's published the first 12 between 1947 and 1958, but rejected the 13th, Starship Troopers. That one was instead published by Putnam. A 14th novel, Podkayne of Mars, is sometimes listed as a "Heinlein juvenile", although Heinlein himself did not consider it to be one.
The magnetosphere of Jupiter is the cavity created in the solar wind by Jupiter's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973.
The exploration of Jupiter has been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2023, has continued with eight further spacecraft missions in the vicinity of Jupiter. All of these missions were undertaken by the National Aeronautics and Space Administration (NASA), and all but two were flybys taking detailed observations without landing or entering orbit. These probes make Jupiter the most visited of the Solar System's outer planets as all missions to the outer Solar System have used Jupiter flybys. On 5 July 2016, spacecraft Juno arrived and entered the planet's orbit—the second craft ever to do so. Sending a craft to Jupiter is difficult, mostly due to large fuel requirements and the effects of the planet's harsh radiation environment.
Galileo's Dream (2009) is a science fiction novel with elements of historical fiction written by Kim Stanley Robinson. In the book, 17th-century scientist Galileo Galilei is visited by far-future time travellers living on the Galilean moons of Jupiter. Italicised portions of the text within the novel are actually translations of Galileo and his contemporaries' own recorded writings.
The exploration of Io, Jupiter's innermost Galilean and third-largest moon, began with its discovery in 1610 and continues today with Earth-based observations and visits by spacecraft to the Jupiter system. Italian astronomer Galileo Galilei was the first to record an observation of Io on January 8, 1610, though Simon Marius may have also observed Io at around the same time. During the 17th century, observations of Io and the other Galilean satellites helped with the measurement of longitude by map makers and surveyors, with validation of Kepler's Third Law of planetary motion, and with measurement of the speed of light. Based on ephemerides produced by astronomer Giovanni Cassini and others, Pierre-Simon Laplace created a mathematical theory to explain the resonant orbits of three of Jupiter's moons, Io, Europa, and Ganymede. This resonance was later found to have a profound effect on the geologies of these moons. Improved telescope technology in the late 19th and 20th centuries allowed astronomers to resolve large-scale surface features on Io as well as to estimate its diameter and mass.
The Jupiter Icy Moons Explorer is an interplanetary spacecraft that was launched on 14 April 2023 from Guiana Space Centre in the French Guiana by the European Space Agency (ESA) with Airbus Defence and Space as the main contractor. The mission is planned to study Ganymede, Callisto, and Europa, three of Jupiter's Galilean moons. They are thought to have significant bodies of liquid water beneath their icy surfaces which would make them potentially habitable environments.
The timeline of the Galileo spacecraft spans its launch in 1989 to the conclusion of its mission when it dove into and destroyed itself in the atmosphere of Jupiter in 2003.
The following outline is provided as an overview of and topical guide to Jupiter:
Tianwen-4, formerly known as Gan De, is a planned interplanetary mission by China to study the Jovian system and its environs, sharing a launch with a spacecraft which will make a flyby of Uranus.
