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

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The within planets (in order of street from the sun, closest come furthest) space Mercury, Venus, Earth and also Mars. After ~ an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The exciting thing is, in some other planetary solution discovered, the gas giants space actually rather close come the sun.

This makes predicting just how our Solar System formed an exciting exercise because that astronomers. Conventional wisdom is that the young sun blew the gases right 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 “hot Jupiters” that orbit nearby to their Sun.

The within Planets:

The 4 inner planets are called terrestrial planets because their surfaces are solid (and, as the name implies, somewhat comparable to planet — although the term have the right to be misleading since each that the 4 has vastly various environments). They’re consisted of mostly of heavy metals such as iron and nickel, and have either no moons or couple of moons. Listed below are quick descriptions of every of this planets based on this information from NASA.

Mercury: Mercury is the smallest earth in our Solar mechanism and also the closest. It rotates slowly (59 planet days) loved one to the moment it takes come rotate roughly the sun (88 days). The planet has no moons, but has a tenuous atmosphere (exosphere) comprise oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, room ENvironment, GEochemistry, and also Ranging) spacecraft is right now orbiting the planet.

The terrestrial planets of our Solar system at roughly relative sizes. Indigenous left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute

Venus: Venus to be once considered a twin world to Earth, until astronomers uncovered its surface is in ~ a lead-melting temperature that 900 degrees Fahrenheit (480 degrees Celsius). The earth is additionally a sluggish rotator, with a 243-day long Venusian day and also an orbit about the sunlight at 225 days. Its atmosphere is thick and contains carbon dioxide and also nitrogen. The planet has no rings or moons and is at this time being saw by the European space Agency’s Venus to express spacecraft.

Earth: Earth is the only planet through life together we understand it, however astronomers have found some nearly Earth-sized planets exterior of our solar system in what could be habitable areas of their corresponding stars. It includes an atmosphere of nitrogen and oxygen, and has one moon and also no rings. Countless spacecraft circle our earth to administer telecommunications, weather information and also other services.

Mars: Mars is a world under extreme study due to the fact that it shows indications of liquid water flowing on its surface in the old past. Today, however, its setting is a wispy mix the carbon dioxide, nitrogen and also argon. It has actually two tiny moons (Phobos and also Deimos) and no rings. A Mars day is slightly much longer than 24 planet hours and also it bring away the planet around 687 earth days to circle the Sun. There’s a little fleet of orbiters and also rovers at Mars right now, consisting of the huge NASA Curiosity rover that landed in 2012.

The external planets of ours Solar device at approximately relative sizes. Indigenous left, Jupiter, Saturn, Uranus and also Neptune. Credit: Lunar and Planetary Institute

The external Planets:

The outer planets (sometimes dubbed Jovian planets or gas giants) are vast planets swaddled in gas. Lock all have actually rings and all of plenty of moons each. Regardless of their size, just two that them room visible there is no telescopes: Jupiter and also Saturn. Uranus and Neptune to be the first planets discovered because antiquity, and also showed astronomers the solar device was enlarge than previously thought. Below are brief descriptions of every of these planets based on this information from NASA.

Jupiter: Jupiter is the largest planet in ours Solar System and spins really rapidly (10 planet hours) family member to that orbit of the sunlight (12 earth years). That is thick atmosphere is mostly consisted of of hydrogen and also helium, perhaps surrounding a terrestrial core that is around Earth’s size. The planet has dozens of moons, part faint rings and also a an excellent Red spot — a raging storm happening because that the previous 400 year at least (since we were may be to watch it with telescopes). NASA’s Juno spacecraft is en route and also will visit there in 2016.

Saturn: Saturn is ideal known for its influential ring device — seven well-known rings through well-defined divisions and gaps in between them. Just how the rings gained there is one topic under investigation. It likewise has dozens of moons. Its atmosphere is mainly hydrogen and also helium, and also it likewise rotates conveniently (10.7 earth hours) loved one to that is time come circle the sunlight (29 planet years). Saturn is right now 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 expose its otherwise pass out ring system, highlighting the level to which the is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.

Uranus: Uranus was very first discovered by william Herschel in 1781. The planet’s day takes about 17 earth hours and one orbit approximately the sun takes 84 earth years. Its mass has water, methane, ammonia, hydrogen and also helium surrounding a rocky core. It has dozens that moons and a pass out ring system. There space no spacecraft slated to visit Uranus appropriate now; the critical visitor to be Voyager 2 in 1986.

Neptune: Neptune is a remote planet that consists of water, ammmonia, methane, hydrogen and helium and also a possible Earth-sized core. The has more than a dozen moons and six rings. The only spacecraft to ever before visit it was NASA’s Voyager 2 in 1989.

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To learn an ext about the planets and missions, check out this links:

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

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CategoriesAstronomy, overview to an are TagsEarth, inner planets, Jupiter, Mars, Mercury, Neptune, outer planets, Saturn, Uranus, Venus

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