A moon is a natural satellite rotating around a planet. While moons vary in size, each moon is
Oberon is the second largest moon of Uranus orbits at a distance of about 584,000 km. Its orbital period is around 13.5 days, coincident with its rotational period. In other words, Oberon is a synchronous satellite, tidally locked, with one face always pointing toward the planet. Composed of roughly half ice and half rock. Oberon has one large mountain that rises about 6 km off the surface. Discovered in 1787 by William Herschel in 1787. The Uranian system has been studied up close only once the spacecraft Voyager 2 took several images of Oberon in January 1986, allowing 40% of the moon’s surface to be mapped. It has a diameter of 1523 km.
The ninth biggest moon in the existing solar system in terms of size is Rhea. Rhea is the second largest of Saturn’s moons, was discovered in the year 1672 by Giovanni Domenico Cassini, an Italian-French astronomer. Rhea is an icy body with a density of about 1.236 g/cm3. The diameter of Rhea is 1528 km. The moon got its name from the Greek mythological character Rhea who is the revered mother of all the gods. On March 6, 2008, NASA announced that Rhea may have a tenuous ring system. This would mark the first discovery of rings about a moon. The first images of Rhea were obtained by Voyager 1 & 2 spacecraft in 1980–1981.
Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of 1,578 kilometer an average of 436,000 kilometers from its planet. It takes the moon about 8.7 days to orbit Uranus, and it is in a synchronous orbit with its planet. Titania was discovered by William Herschel on January 11, 1787. The satellite was named after Titania, a character from William Shakespeare’s A Midsummer Night’s Dream. Uranus is unique in that it is the only planet whose moons were not named after figures from Greek mythology. Instead, they were named after characters from a poem by Alexander Pope and from plays by William Shakespeare. The moon was not given its current name until 1852 by William Herschel’s son who suggested names for four of Uranus’ satellites. Scientists believe the moon is about half water ice and half a dense material such as rock. There are fewer craters on Titania than are on Oberon, which tells scientists that Titania is actually the younger moon. Like on Oberon, the surface features on Titania have been named after characters in works by Shakespeare; all of the physical features are named after female characters. The largest crater on the satellite discovered so far is Gertrude, named after Hamlet’s mother, which is approximately 326 kilometers in diameter. The only probe to explore Titania was the Voyager 2, which took many pictures of the satellite in 1989.
Triton is the largest of Neptune’s 13 moons. Triton was discovered by British astronomer William Lassell on October 10, 1846 just 17 days after the discovery of Neptune. It was named after the Greek god Triton, who was the son of Poseidon. It is the only large moon in our solar system that orbits in the opposite direction of its planet’s rotation. Triton has a diameter of 2,700 km. Triton is one of the coolest objects in our solar system. It is so cold that most of Triton’s nitrogen is condensed as frost, giving its surface an icy sheen that reflects 70 percent of the sunlight that hits it. Triton is the coldest known object in the Solar System. Its surface temperature averages only -391F (-235C).
Europa was discovered by Galileo Galilei in January 1610. Progressively better observations of Europa have occurred over the centuries by Earth-bound telescopes, and by space probe flybys starting in the 1970s. It is only slightly smaller than our own moon. On 8 September 2014, NASA reported finding evidence confirming earlier reports of plate tectonics in Europa’s thick ice shell – the first sign of such geological activity on another world other than Earth. Europa orbits Jupiter in just over 3.5 days, with an orbital radius of about 670,900 km. Europa has a diameter of 3,100 km.
The Moon is Earth’s only natural satellite. Our planet’s trusty companion is an airless, silent world without any signs of life. Because of its small size, the Moon’s force of attraction is too weak to hold the gases it would need to form an atmosphere. The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. The Moon is a spherical rocky body, probably with a small metallic core, revolving around Earth in a slightly eccentric orbit at a mean distance of about 384,000 km. It’s diameter is 3475 km.
Io is a large, rocky, volcanically active moon of Jupiter. It has a diameter of 3,636 km. Io’s mean distance from Jupiter is 422,000 km. It was discovered in 1610 by Galileo Galilei, along with the other Galilean satellites. Further observations have been made by Cassini–Huygens in 2000 and New Horizons in 2007, as well as from Earth-based telescopes and the Hubble Space Telescope as technology has advanced. It has the highest density of all the moons, and is the driest known object in the Solar System. It was named after the mythological character Io, a priestess of Hera who became one of Zeus’s lovers.
With a diameter of over 4,800 km, Callisto is the third largest satellite in the solar system and is almost the size of Mercury. It was discovered in 1610 by Galileo Galilei. Callisto is the outermost of the Galilean satellites (Ganymede, Europa, Io, Callisto). Callisto is named for the beautiful daughter of Lycaon, who followed the chaste goddess of the hunt, Artemis. Unfortunately, since Callisto was seduced by Zeus (the Greek equivalent of the Roman god Jupiter) and became pregnant she was banished by Artemis. Zeus changed Callisto into a bear to protect her from his wife Hera’s jealousy. Later, Zeus placed Callisto and their son in the sky, and mother and son became Ursa Major and Ursa Minor (Great Bear and Little Bear).
Titan is Saturn’s largest moon and the second largest in the solar system. It was discovered on March 25, 1655 by the Dutch astronomer Christiaan Huygens. Titan is the only natural satellite known to have a dense atmosphere. Titan’s atmosphere is active and complex, and it is mainly composed of nitrogen (95 percent) and methane (5 percent). Titan also has a presence of organic molecules that contain carbon and hydrogen, and that often include oxygen and other elements similar to what is found in Earth’s atmosphere and that are essential for life. It has a diameter of 5,152 km.
1. GanymedeGanymede is a satellite of Jupiter and the largest satellite in our solar system. It is larger than Mercury and Pluto, and three-quarters the size of Mars. It has a diameter of 5,268 km. It orbiting at about 1.070 million km and takes about seven Earth days to orbit Jupiter. Ganymede is composed of approximately equal amounts of silicate rock and water ice. It is a fully differentiated body with an iron-rich, liquid core, and it might have ice and oceans stacked up in several layers. Ganymede was discovered by Galileo Galilei on Jan. 7, 1610. The discovery, along with three other Jovian moons, was the first time a moon was discovered orbiting a planet other than Earth. Galileo’s discovery eventually led to the understanding that planets orbit the sun, instead of our solar system revolving around Earth. Galileo called this moon Jupiter III. When the numerical naming system was abandoned in the mid-1800s, the moon was named after Ganymede, a Trojan prince in Greek mythology. Zeus, a counterpart of Jupiter in Roman mythology, carried Ganymede, who had taken the form of an eagle, to Olympus, where he became a cupbearer to the Olympian gods and one of Zeus’ lovers.