Why are these four called Galilean moons?
The planet Jupiter's four largest moons, or satellites, are called the Galilean moons, after Italian astronomer Galileo Galilei, who observed them in 1610. The German astronomer Simon Marius apparently discovered them around the same time.
Ganymede, Callisto, Io and Europa. Galileo originally called the Jupiter's moons the "Medicean planets", after the Medici family and referred to the individual moons numerically as I, II, III and IV. Galileo's naming system would be used for a couple of centuries.
Credit: Pixabay. Jupiter is monstrously large, so much so that it is more than twice as massive as all other planets in the solar system combined. Consequently, it has an equally massive gravitational pull that helped it capture a myriad of satellites. By the latest count, the gas giant has 79 confirmed moons.
Visible with common binoculars, 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.
He proposed to name them after his patrons the Medicis and astronomers called them the Medicean Stars through much of the seventeenth century, although in his own notes Galileo referred to them by the Roman numerals I, II, III, and IV, in order of their distance from Jupiter.
The names that eventually prevailed were chosen by Simon Marius, who claimed to have discovered the moons at the same time as Galileo. He named them after lovers of the god Zeus (the Greek equivalent of Jupiter): Io, Europa, Ganymede, and Callisto, in his Mundus Jovialis, published in 1614.
The choice of names is often determined by a satellite's discoverer; however, historically some satellites were not given names for many years after their discovery; for instance, Titan was discovered by Huygens in 1655, but was not named until 1847, almost two centuries later.
Ganymede is one of three jovian moons that may hold hidden oceans, all potential habitats for life. They are the targets of the $1.6 billion Jupiter Icy Moons Explorer (Juice), a European Space Agency (ESA) mission set for a 13 April launch on an Ariane 5 rocket from French Guiana.
Astronomers may find more moons around Jupiter in the future. Io, Ganymede and Callisto are the largest of Jupiter's moons. These 4 moons are each bigger than the Earth's moon.
saturn: 7 moons work together to keep Saturn's largest ring in place - The Economic Times.
Is there life on the Galilean moons?
Although some have speculated that life may be possible within the atmosphere of Jupiter itself, more likely candidates are the four icy Galilean moons around it. All four moons are extremely cold, and all have thin atmospheres. Nevertheless, they are all tantalising prospects for finding life beyond Earth.
Once this gas and dust had condensed to form Jupiter, the leftover material coalesced and grew over time to form the Galilean moons. This makes Jupiter's largest moons likely as old of the rest of the Solar System: about 4.5 billion years old.
Composition and origin: The rings are mostly dust and small, dark particles kicked up by meteorite impacts on the planet's small ring moons. Ring material must be continually replenished after it is destroyed by Jupiter's radiation or gets pushed into the planet, giving the rings an age of less than 1 million years.
Galileo's discoveries were extremely controversial because they indicated that the Earth was not at the center of the Universe: moons orbited Jupiter, and Venus orbited the Sun; thus, it seemed more logical that Earth also orbited the Sun. This was in conflict with the teachings of the Catholic Church.
Their orbital shapes range from nearly perfectly circular to highly eccentric and inclined, and many revolve in the direction opposite to Jupiter's rotation (retrograde motion). Orbital periods range from seven hours (taking less time than Jupiter does to rotate around its axis), to almost three Earth years.
Galileo's discoveries about the Moon, Jupiter's moons, Venus, and sunspots supported the idea that the Sun - not the Earth - was the center of the Universe, as was commonly believed at the time. Galileo's work laid the foundation for today's modern space probes and telescopes.
The Full Moon Names we use in the Almanac come from the Algonquin tribes who lived in regions from New England to Lake Superior. They are the names the Colonial Americans adapted most. Note that each full Moon name was applied to the entire lunar month in which it occurred.
Jupiter has only a couple of well defined rings with faint 'gossamer' rings surrounding them. Saturn on the other hand has dozens of distinct rings of varying thickness, density and composition.
Simon Marius claimed to have observed Jupiter's moon as early as late November 1609 (about five weeks prior to Galileo) and had begun recording his observations in January 1610 at about the same time Galileo was first making his observations.
Earth is the only planet whose English name does not derive from Greek/Roman mythology.
Is the Earth named after a god?
Earth is the only planet in our solar system not named after a Greco-Roman deity. The name used in Western academia during the Renaissance was Tellus Mater or Terra Mater, the Latin for “earth mother”, i.e. “Mother Earth”, goddess of the earth in ancient Roman religion and mythology.
The United States has the most satellites orbiting Earth. The 2,804 satellites that are owned or operated by an entity from the U.S. make up more than half of the total amount of space satellites that are currently in orbit.
Scientists believe several moons within our solar system have significant subsurface liquid water deposits. Saturn's moon Enceladus and Jupiter's moon Europa are two examples. Both appear to have salty, liquid oceans covered with thick layers of ice at the surface.
Thus, Titan could potentially harbor environments with conditions suitable for life—meaning both life as we know it (in the subsurface ocean) and life as we don't know it (in the hydrocarbon liquid on the surface).
Among the planets, Earth is unique for its oxygen-rich atmosphere. None of the other terrestrial planets contain much oxygen in their atmosphere, despite oxygen being a rather common element in the cosmos. Part of the reason for this is that oxygen binds easily with other elements.
But it is the names that Simon Marius proposed for the moons – names suggested to him by fellow astronomer Johannes Kepler – that we use today: Io, Europa, Ganymede, and Callisto. The four moons collectively are referred to as the Galilean moons. (Jupiter now has 53 named moons and another 26 awaiting official names.)
The Galilean satellites were first seen by the Italian astronomer Galileo Galilei in 1610. Shown from left to right in order of increasing distance from Jupiter, Io is closest, followed by Europa, Ganymede, and Callisto.
The name for India's first satellite 'Aryabhata' was chosen by the then Prime Minister Indira Gandhi who was suggested three names. The satellite was named after the 5th century Indian astronomer and mathematician Aryabhata.
