The inner planets, Mercury, Venus, Earth and Mars, are made up of silicate rock and heavy metals such as iron and nickel, whereas the outer planets, Jupiter, Saturn, Uranus and Neptune, are made up mostly of gases, according to Universe Today. The outer planets are subdivided into gas giants, comprised mostly of hydrogen and helium, and ice giants, comprised mostly of methane, ammonia and water.Continue Reading
Despite being made up mostly of gases, the outer planets have a rock core. However, they are still less dense and located further away from the sun than the inner or terrestrial planets. Astronomers are able to to determine how planets formed by studying the structure of the solar system and other younger planetary systems that are in varying stages of development.
The dominant theory, according to HowStuffWorks, states that solar wind emanating from the sun blew light elements, mostly gases, away into the outer orbits. Gravity then drew these elements in causing them to form giant balls. The discovery of hot Jupiters in 1995, however, put a dent in this theory. Hot Jupiters are a type of gas giant that orbit very close to the sun. Astronomers theorize that such planets form far away from the sun and then move closer through orbital migration.Learn more about Planets
Nicknames for the eight planets in the solar system are Swift Planet for Mercury, Morning Star and Evening Star for Venus, Blue Planet for Earth, Red Planet for Mars, Giant Planet for Jupiter, Ringed Planet for Saturn, Ice Giant for Uranus and Big Blue Planet for Neptune. Pluto was once considered a planet and had the nickname Ice Planet, but it is now classified as a dwarf planet.Full Answer >
The order of the planets from the sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Before 2006, Pluto was considered to be a planet; as of 2014, it is considered to be a dwarf planet.Full Answer >
Beginning with the planet closest to the Sun and moving outward, the order of the planets is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Before its reclassification as a dwarf planet by the International Astronomical Union in 2006, Pluto was considered the ninth and most distant planet.Full Answer >
The eight described planets all orbit the Sun at different distances; Mercury is the closest planet to the sun, followed by Venus, then Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The distances of the planets are normally measured in kilometers, because scientists use metric measurements. However, scientists also use a unit called an “astronomical unit,” which is equal to the distance between Earth and the sun.Full Answer >