Mercury (☿) is the closest planet to the Sun but not the hottest. That distinction goes to Venus. The planet was named after the Roman messenger of the gods because it moves quickly through the sky. Mercury is a small, grayish planet that is often said to resemble the Earth’s Moon. However, that is where the similarities end. It is now suspected that Mercury is the remnant of a much larger planet that lost its crust in a collision with a planetesimal some 4.5 billion years ago.
Venus (♀), the second planet from the Sun, is the hottest planet because its atmosphere tends to trap heat. Named after the Roman goddess of beauty, Venus is the brightest planet. In fact, the only celestial body that is brighter is the Moon. Venus is around the same size as Earth with similar gravity, causing it to be referred to as Earth’s twin.
Earth (♁) is the third rock from the Sun. Its name is derived from the Old English word Eorða (pronounced Eortha) which means land. In Latin, Portuguese, and Italian it is Terra. In French it is Terre. In Spanish it is Tierra, In German, Erde. It is the only planet where life has been confirmed to exist. Roughly two-thirds of Earth’s surface is covered with oceans, and so far Earth is the only place where liquid water is known to exist.
Mars (♂), the fourth planet from the Sun, was named after the Roman god of war because of its red color, which is caused by rust in the rocks on the surface. Since it is the closest planet to Earth, people have long wondered if life could exist on Mars. Although no life has been discovered so far, some people still think that there may be life on Mars. Mars is also suspected to have supported vast oceans in the distant past.
Ceres (⚳), the fifth planet and the smallest, with a diameter of 950 kilometers, is named for the Roman goddess of growing plants, the harvest, and motherly love. It lies in the heart of the asteroid belt and has been designated a planet, shortly after its discover, as were Pallas, Juno, and Vesta, then an asteroid or minor planet, and is once again classified as a planet, albeit a dwarf planet.
Jupiter (♃), a gas giant, is the largest planet in this solar system. It was named after the Roman king of the gods, most likely due to its brightness and golden hue. Jupiter has 63 moons, one of which, Ganymede, is the solar system’s largest moon. Jupiter is also home to an enormous storm, the Great Red Spot, which has been raging for over two hundred years.
Saturn (♄), the sevent planet from the Sun, was named after the Roman god of agriculture and harvest, Saturnus. Saturnus was a Titan and father of Jupiter. Saturn, like Jupiter, is a gas giant and therefore does not have a solid surface, although both are suspected of having rocky cores. The most distinctive feature of the planet is its rings, which are composed of small pieces of rock and ice.
Uranus (♅), the third largest planet, is also an ice giant. While its atmosphere contains hydrogen and helium, like Jupiter and Saturn, it also has large quantities of water, methane, and ammonia. Uranus was named after the Greek “Father Sky” Ouranous, the father of Cronus (Saturn) and the grandfather of Zeus (Jupiter). Uranus orbits very slowly; it takes the planet 84 years to circle the Sun. Its axis of rotation is nearly parallel to the orbital plane of the Solar System. It is suspected that an Earth sized protoplanet collided with Uranus.
Neptune (♆) is the ninth planet from the Sun. It was named after the Roman god of the sea; this is not surprising because it is bright blue, reminding one of a beautiful ocean. Neptune has four rings, although they are difficult to see. It was the first planet found by mathematical prediction.
Pluto (♇), the second dwarf planet from the Sun, was named for the Roman god of the underworld. It travels the Solar System in an highly elliptical and eccentric orbit that takes it inside of Neptune’s orbit on occasions. It mass has been determined to be just under 0.24⊕.
Haumea, the eleventh planet from the Sun, was named for the Hawaiian goddess of fertility and childbirth, is a dwarf planet with one third the mass of Pluto and lies in the Kuiper belt. Like other Plutinos it crosses Neptune’s orbit on occasion due to their 2:3 resonance with the larger planet.
Makemake is the fourth dwarf planet from the Sun and is named for the Rapanui creator of humanity and god of fertility. It follows a highly inclined (29°) orbit.
Eris, at present the last planet in our star system and is named for the Greek goddess of discord. It is 27% more massive than Pluto or about 0.27⊕. It along with its moon, Dysnomia, are the most distant known natural objects in the Solar System, with the exception of a few comets.