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

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The inside planets (in stimulate of distance from the sun, closest to furthest) room Mercury, Venus, Earth and Mars. ~ an asteroid belt comes the external planets, Jupiter, Saturn, Uranus and also Neptune. The interesting thing is, in some various other planetary systems discovered, the gas giants are actually quite close come the sun.

This renders predicting just how our Solar System developed an exciting exercise because that astronomers. Conventional wisdom is that the young sun blew the gases into the outer fringes the the Solar System and also that is why there space such big gas giants there. However, part extrasolar systems have actually “hot Jupiters” that orbit close to your Sun.


The within Planets:

The four inner planets are dubbed terrestrial planets since their surfaces room solid (and, as the surname implies, somewhat similar to earth — although the term have the right to be misleading due to the fact that each that the 4 has vastly different environments). They’re made up mostly of hefty metals such together iron and nickel, and have one of two people no moons or couple of moons. Below are brief descriptions of every of this planets based upon this details from NASA.

Mercury: Mercury is the smallest world in ours Solar system and additionally the closest. That rotates progressively (59 earth days) loved one to the moment it takes to rotate around the sunlight (88 days). The planet has actually no moons, yet has a tenuous atmosphere (exosphere) comprise oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, room ENvironment, GEochemistry, and Ranging) spacecraft is right now orbiting the planet.

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The terrestrial planets of our Solar device at about relative sizes. Native left, Mercury, Venus, Earth and also Mars. Credit: Lunar and Planetary Institute

Venus: Venus was once thought about a twin earth to Earth, till astronomers uncovered its surface is in ~ a lead-melting temperature that 900 degrees Fahrenheit (480 degrees Celsius). The planet is additionally a slow-moving rotator, v a 243-day lengthy Venusian day and also an orbit around the sun at 225 days. Its environment is thick and contains carbon dioxide and nitrogen. The planet has no ring or moons and is right now being saw by the European space Agency’s Venus refer spacecraft.


Earth: Earth is the only planet through life as we know it, yet astronomers have discovered some almost Earth-sized planets outside of our solar mechanism in what might be habitable areas of their particular stars. It includes an setting of nitrogen and oxygen, and has one moon and no rings. Plenty of spacecraft one our planet to administer telecommunications, weather information and other services.

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

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

The outer Planets:

The external planets (sometimes dubbed Jovian planets or gas giants) are substantial planets swaddled in gas. Lock all have actually rings and all of plenty of moons each. Regardless of their size, just two of them room visible without telescopes: Jupiter and also Saturn. Uranus and Neptune to be the very first planets discovered due to the fact that antiquity, and also showed astronomers the solar device was larger than formerly thought. Below are brief descriptions of every of this planets based ~ above this info from NASA.


Jupiter: Jupiter is the largest planet in ours Solar System and also spins very rapidly (10 earth hours) relative to that orbit of the sun (12 planet years). That thick setting is mostly consisted of of hydrogen and helium, perhaps surrounding a terrestrial core that is around Earth’s size. The planet has actually dozens of moons, part faint rings and a great Red clues — a raging storm happening because that the past 400 year at least (since us were maybe to view it through telescopes). NASA’s Juno spacecraft is en route and will visit there in 2016.

Saturn: Saturn is finest known because that its influential ring mechanism — seven recognized rings with well-defined divisions and gaps in between them. Just how the rings acquired there is one topic under investigation. It also has dozens the moons. Its atmosphere is greatly hydrogen and helium, and also it likewise rotates quickly (10.7 planet hours) relative to that time come circle the sunlight (29 earth years). Saturn is at this time being checked out by the Cassini spacecraft, which will fly closer to the planet’s rings in the comes years.

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Near-infrared views of Uranus expose its otherwise faint ring system, highlighting the level 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 job takes about 17 earth hours and also one orbit approximately the sunlight takes 84 earth years. Its mass consists of water, methane, ammonia, hydrogen and helium neighboring a rocky core. It has dozens that moons and a pass out ring system. There are no spacecraft slated to visit Uranus best now; the critical visitor to be Voyager 2 in 1986.


Neptune: Neptune is a distant planet that consists of water, ammmonia, methane, hydrogen and also helium and a possible Earth-sized core. The has much more than a dozen moons and also six rings. The only 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 also missions, check out these links:

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


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CategoriesAstronomy, guide to space TagsEarth, inner planets, Jupiter, Mars, Mercury, Neptune, external planets, Saturn, Uranus, Venus

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