In our Solar System, astronomers frequently divide the planets into two groups — the inner planets and the external planets. The within planets room closer to the Sun and are smaller and also rockier. The outer planets are more away, larger and also made up mainly of gas.

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The inside planets (in stimulate of distance from the sun, closest come furthest) room Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The exciting thing is, in some various other planetary equipment discovered, the gas giants are actually fairly close come the sun.

This provides predicting how our Solar System created an interesting exercise for astronomers. Traditional wisdom is the the young sunlight blew the gases into the external fringes of the Solar System and also that is why there space such huge gas giants there. However, some extrasolar systems have actually “hot Jupiters” the orbit near to their Sun.

The inside Planets:

The 4 inner planets are dubbed terrestrial planets due to the fact that their surfaces room solid (and, as the name implies, somewhat similar to earth — return the term deserve to be misleading since each of the 4 has vastly different environments). They’re made up mostly of hefty metals such as iron and also nickel, and have either no moons or few moons. Below are quick descriptions of each of these planets based on this information from NASA.

Mercury: Mercury is the smallest planet in ours Solar mechanism and likewise the closest. The rotates progressively (59 earth days) family member to the time it takes come rotate approximately the sun (88 days). The planet has no moons, yet has a tenuous setting (exosphere) include oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, an are ENvironment, GEochemistry, and also Ranging) spacecraft is at this time orbiting the planet.

The terrestrial planets of ours Solar mechanism at approximately relative sizes. Native left, Mercury, Venus, Earth and also Mars. Credit: Lunar and also Planetary Institute

Venus: Venus was once thought about a twin earth to Earth, till astronomers discovered its surface ar is at a lead-melting temperature of 900 levels Fahrenheit (480 levels Celsius). The planet is additionally a slow rotator, v a 243-day lengthy Venusian day and an orbit around the sunlight at 225 days. Its atmosphere is thick and contains carbon dioxide and nitrogen. The planet has actually no ring or moons and also is currently being went to by the European space Agency’s Venus refer spacecraft.

Earth: Earth is the only planet v life together we recognize it, however astronomers have discovered some nearly Earth-sized planets exterior of our solar system in what can be habitable regions of their respective stars. It has an setting of nitrogen and oxygen, and also has one moon and also no rings. Many spacecraft one our world to administer telecommunications, weather information and also other services.

Mars: Mars is a earth under extreme study because it shows indicators of liquid water flow on its surface in the old past. Today, however, its atmosphere is a wispy mix that carbon dioxide, nitrogen and also argon. It has actually two small moons (Phobos and also Deimos) and also no rings. A Mars day is slightly longer than 24 earth hours and also it take away the planet around 687 earth days to circle the Sun. There’s a tiny fleet of orbiters and also rovers in ~ Mars ideal now, including the big NASA Curiosity rover that landed in 2012.

The outer planets of our Solar device at approximately relative sizes. Native left, Jupiter, Saturn, Uranus and also Neptune. Credit: Lunar and also Planetary Institute

The outer Planets:

The outer planets (sometimes dubbed Jovian planets or gas giants) are substantial planets swaddled in gas. Castle all have actually rings and every one of plenty that moons each. Despite their size, just two of them are visible without telescopes: Jupiter and also Saturn. Uranus and Neptune were the an initial planets discovered since antiquity, and showed astronomers the solar system was larger than previously thought. Below are quick descriptions of each of these planets based on this information from NASA.

Jupiter: Jupiter is the biggest planet in our Solar System and spins an extremely rapidly (10 earth hours) relative to that is orbit the the sunlight (12 earth years). Its thick atmosphere is mostly consisted of of hydrogen and helium, perhaps bordering a terrestrial main point that is around Earth’s size. The planet has actually dozens of moons, part faint rings and also a good Red point out — a raging storm happening for the past 400 years at the very least (since us were maybe to see it with telescopes). NASA’s Juno spacecraft is en route and will visit there in 2016.

Saturn: Saturn is best known for its significant ring device — seven recognized rings with well-defined divisions and gaps between them. Exactly how the rings obtained there is one subject under investigation. It likewise has dozens of moons. Its environment is greatly hydrogen and helium, and also it also rotates quickly (10.7 earth hours) loved one to its time to circle the sun (29 planet years). Saturn is at this time being went to by the Cassini spacecraft, which will fly closer to the planet’s ring in the comes years.

Near-infrared views of Uranus reveal its otherwise pass out ring system, highlighting the extent to which that is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.

Uranus: Uranus was an initial discovered by wilhelm Herschel in 1781. The planet’s day takes about 17 planet hours and also one orbit roughly the sunlight takes 84 planet years. The mass includes water, methane, ammonia, hydrogen and also helium bordering a rocky core. It has actually dozens that moons and a faint ring system. There room no spacecraft slated come visit Uranus right now; the last visitor to be Voyager 2 in 1986.

Neptune: Neptune is a remote planet that includes water, ammmonia, methane, hydrogen and also helium and also a feasible Earth-sized core. The has much more than a dozen moons and also six rings. The just spacecraft to ever visit it to be NASA’s Voyager 2 in 1989.

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To learn much more about the planets and missions, inspect out this links:

Solar device Exploration: Planets (NASA)NASA Photojournal (NASA)Missions (NASA)Space science (European an are Agency)USGS Astrogeology (U.S. Geological Survey)The Solar System and Its Planets (European space Agency)

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CategoriesAstronomy, guide to room TagsEarth, within planets, Jupiter, Mars, Mercury, Neptune, external planets, Saturn, Uranus, Venus

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