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Sun
The Sun is the closest star to Earth, at a mean distance from our planet of 149.60 million kilometers (92.96 million miles). This distance is known as an astronomical unit (abbreviated AU), and sets the scale for measuring distances all across the solar system. The Sun, a huge sphere of mostly ionized gas, supports life on Earth. It powers photosynthesis in green plants, and is ultimately the source of all food and fossil fuel. The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, and climate.
1Sun.png
# VOL MEAN RADIUS: 696,000 km.
# MASS: 332,830 (Earth=1)
# DENSITY: 1.41 (g/cm^3)
# GRAVITY: 27.9 (Earth=1)
# ESCAPE VELOCITY: 617.7 (km/s)
# VISUAL MAGNITUDE: 26.74
# ABSOLUTE MAGNITUDE: +4.83
# SPECTRAL TYPE: G2 V
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Mercury
The small and rocky planet Mercury is the closest planet to the Sun; it speeds around the Sun in a wildly elliptical (non-circular) orbit that takes it as close as 47 million km and as far as 70 million km from the Sun. Mercury completes a trip around the Sun every 88 days, speeding through space at nearly 50 km per second, faster than any other planet. Because it is so close to the Sun, temperatures on its surface can reach a scorching 467 degrees Celsius. But because the planet has hardly any atmosphere to keep it warm, nighttime temperatures can drop to a frigid -170 degrees Celsius.
2Mercury.png
# MEAN RADIUS: 2439.7 km
# MASS: 0.055 (Earth=1)
# DENSITY: 5.43 (g/cm^3)
# GRAVITY: 0.376 (Earth=1)
# ORBIT PERIOD: 87.97 (Earth days)
# ROTATION PERIOD: 58.65 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 0.387 au
# ECCENTRICITY OF ORBIT: 0.206
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Venus
At first glance, if Earth had a twin, it would be Venus. The two planets are similar in size, mass, composition, and distance from the Sun. But there the similarities end. Venus has no ocean. Venus is covered by thick, rapidly spinning clouds that trap surface heat, creating a scorched greenhouse-like world with temperatures hot enough to melt lead and pressure so intense that standing on Venus would feel like the pressure felt 900 meters deep in Earth's oceans. These clouds reflect sunlight in addition to trapping heat. Because Venus reflects so much sunlight, it is usually the brightest planet in the sky
3Venus.png
# MEAN RADIUS: 6051.9 km
# MASS: 0.814 (Earth=1)
# DENSITY: 5.24 (g/cm^3)
# GRAVITY: 0.903 (Earth=1)
# ORBIT PERIOD: 224.7 (Earth days)
# ROTATION PERIOD: 243.0 R (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 0.723 au
# ECCENTRICITY OF ORBIT: 0.007
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Earth
Earth is the third planet from the Sun and the fifth largest in the solar system. Earth's diameter is just a few hundred kilometers larger than that of Venus. The four seasons are a result of Earth's axis of rotation being tilted more than 23 degrees. Earth, our home planet, is the only planet in our solar system known to harbor life - life that is incredibly diverse. All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space. Earth is made up of complex, interactive systems that are often unpredictable. Air, water, land, and life - including humans - combine forces to create a constantly changing world that we are striving to understand.
4Earth.png
# EQUATORIAL RADIUS: 6378.140 km
# MASS: 1.000 (Earth=1)
# DENSITY: 5.52 (g/cm^3)
# GRAVITY: 1.000 (Earth=1)
# ORBIT PERIOD: 365.26 (Earth days)
# ROTATION PERIOD: 1.00 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 1.000 au
# ECCENTRICITY OF ORBIT: 0.017
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Mars
The red planet Mars is a small rocky body once thought to be very Earth-like. Like the other "terrestrial" planets - Mercury, Venus, and Earth - its surface has been changed by volcanism, impacts from other bodies, movements of its crust, and atmospheric effects such as dust storms. It has polar ice caps that grow and recede with the change of seasons; areas of layered soils near the Martian poles suggest that the planet's climate has changed more than once, perhaps caused by a regular change in the planet's orbit. Martian tectonism - the formation and change of a planet's crust - differs from Earth's. Where Earth tectonics involve sliding plates that grind against each other or spread apart in the seafloors, Martian tectonics seem to be vertical, with hot lava pushing upwards through the crust to the surface. Periodically, great dust storms engulf the entire planet. The effects of these storms are dramatic, including giant dunes, wind streaks, and wind-carved features.
5Mars.png
# MEAN RADIUS: 3388.0 km
# MASS: 0.108 (Earth=1)
# DENSITY: 3.94 (g/cm^3)
# GRAVITY: 0.380 (Earth=1)
# ORBIT PERIOD: 686.98 (Earth days)
# ROTATION PERIOD: 1.026 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 1.524 au
# ECCENTRICITY OF ORBIT: 0.093
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Jupiter
The most massive planet in our solar system, with four planet-sized moons and many smaller moons, Jupiter forms a kind of miniature solar system. Jupiter resembles a star in composition. In fact, if it had been about eighty times more massive, it would have become a star rather than a planet. On January 7, 1610, using his primitive telescope, astronomer Galileo Galilei saw four small 'stars' near Jupiter. He had discovered Jupiter's four largest moons, now called Io, Europa, Ganymede, and Callisto. Collectively, these four moons are known today as the Galilean satellites. Io is the most volcanically active body in our solar system. Ganymede is the largest planetary moon and is the only moon in the solar system known to have its own magnetic field. A liquid ocean may lie beneath the frozen crust of Europa. Icy oceans may also lie deep beneath the crusts of Callisto and Ganymede. In 2003 alone, astronomers discovered 23 new moons orbiting the giant planet, giving Jupiter a total moon count of 63 - the most in the solar system. The numerous small outer moons may be asteroids captured by the giant planet's gravity.
6Jupiter.png
# MEAN RADIUS: 69911 km
# MASS: 317.8 (Earth=1)
# DENSITY: 1.31 (g/cm^3)
# GRAVITY: 2.34 (Earth=1)
# ORBIT PERIOD: 11.86 (Earth years)
# ROTATION PERIOD: .414 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 5.2 au
# ECCENTRICITY OF ORBIT: 0.004
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Saturn
Saturn was the most distant of the five planets known to the ancients. In 1610, Italian astronomer Galileo Galilei was the first to gaze at Saturn through a telescope and saw a pair of objects on either side of the planet. He sketched them as separate spheres and wrote that Saturn appeared to be triple-bodied. In 1659, Dutch astronomer Christiaan Huygens, using a more powerful telescope than Galileo's, proposed that Saturn was surrounded by a thin, flat ring. In 1675, Italian-born astronomer Jean-Dominique Cassini discovered a 'division' between what are now called the A and B rings. It is now known that the gravitational influence of Saturn's moon Mimas is responsible for the Cassini Division, which is 4,800 kilometers (3,000 miles) wide. Like Jupiter, Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 500 meters (1,600 feet) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters, or 360 feet, per second.)
7Saturn.png
# MEAN RADIUS: 58232 km
# MASS: 95.2 (Earth=1)
# DENSITY: 0.69 (g/cm^3)
# GRAVITY: 1.16 (Earth=1)
# ORBIT PERIOD: 29.46 (Earth years)
# ROTATION PERIOD: 0.436 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 9.53 au
# ECCENTRICITY OF ORBIT: 0.056
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Uranus
Uranus has been revealed as a dynamic world with some of the brightest clouds in the outer solar system and 11 rings. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel and as the seventh planet from the Sun is so distant that it takes 84 years to complete one orbit. Uranus, with no solid surface, is one of the gas giant planets (the others are Jupiter, Saturn, and Neptune). The atmosphere of Uranus is composed primarily of hydrogen and helium, with a small amount of methane and traces of water and ammonia. Uranus gets its blue-green color from methane gas. Sunlight is reflected from Uranus' cloud tops, which lie beneath a layer of methane gas. As the reflected sunlight passes back through this layer, the methane gas absorbs the red portion of the light, allowing the blue portion to pass through, resulting in the blue-green color that we see.  The bulk (80 per-cent or more) of the mass of Uranus is contained in an extended liquid core consisting primarily of 'icy' materials (water, methane, and ammonia), with higher-density material at depth.
8Uranus.png
# MEAN RADIUS: 25362 km
# MASS: 14.48 (Earth=1)
# DENSITY: 1.28 (g/cm^3)
# GRAVITY: 1.15 (Earth=1)
# ORBIT PERIOD: 84.01 (Earth years)
# ROTATION PERIOD: 0.72 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 19.18 au
# ECCENTRICITY OF ORBIT: 0.047
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Neptune
The eighth planet from the Sun, Neptune was the first planet located through mathematical predictions rather than through regular observations of the sky. (Galileo had recorded it as a fixed star during observations with his small telescope in 1612 and 1613.) When Uranus didn't travel exactly as astronomers expected it to, a French mathematician, Urbain Joseph Le Verrier, proposed the position and mass of another as yet unknown planet that could cause the observed changes to Uranus' orbit. After being ignored by French astronomers, Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, its largest moon, Triton, was also discovered. Nearly 4.5 billion kilometers (2.8 billion miles) from the Sun, Neptune orbits the Sun once every 165 years. It is invisible to the naked eye because of its extreme distance from Earth. Interestingly, due to Pluto's unusual elliptical orbit, Neptune is actually the farthest planet from the Sun for a 20-year period out of every 248 Earth years.
9Neptune.png
# MEAN RADIUS: 24622 km
# MASS: 17.2 (Earth=1)
# DENSITY: 1.66 (g/cm^3)
# GRAVITY: 1.19 (Earth=1)
# ORBIT PERIOD: 164.79 (Earth years)
# ROTATION PERIOD: .67 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 30.058 au
# ECCENTRICITY OF ORBIT: 0.009
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Pluto
Discovered by American astronomer Clyde Tombaugh in 1930, Pluto takes 248 years to orbit the Sun. Pluto's most recent close approach to the Sun was in 1989. Between 1979 and 1999, Pluto's highly elliptical orbit brought it closer to the Sun than Neptune, providing rare opportunities to study this small, cold, distant world and its companion moon, Charon. Once known as the smallest, coldest, and most distant planet from the Sun, Pluto has a dual identity, not to mention being enshrouded in controversy since its discovery in 1930. On August 24, 2006, the International Astronomical Union (IAU) formally downgraded Pluto from an official planet to a dwarf planet. According to the new rules a planet meets three criteria: it must orbit the Sun, it must be big enough for gravity to squash it into a round ball, and it must have cleared other things out of the way in its orbital neighborhood. The latter measure knocks out Pluto and 2003UB313 (Eris), which orbit among the icy wrecks of the Kuiper Belt, and Ceres, which is in the asteroid belt.
10Pluto.png
# MEAN RADIUS: 1150 km
# MASS: 0.0025 (Earth=1)
# DENSITY: 2.03 (g/cm^3)
# GRAVITY: ? (Earth=1)
# ORBIT PERIOD: 247.7 (Earth years)
# ROTATION PERIOD: 6.39 (Earth days)
# SEMIMAJOR AXIS OF ORBIT: 39.44 au
# ECCENTRICITY OF ORBIT: 0.248
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Small Bodies
A huge number of small bodies called asteroids and comets also exist in the Solar System. Asteroids are rocky fragments left over from the formation of the solar system about 4.6 billion years ago and most of them can be found orbiting the Sun in a belt between Mars and Jupiter called the Asteroid Belt or Main Belt. There are more than 90,000 numbered asteroids. Comets are dirty-ice leftovers from the formation of our solar system and may yield important clues about the formation of our solar system. Around a dozen "new" comets are discovered each year. Short-period comets are more predictable because they take less than 200 years to orbit the Sun. Most come from a region of icy bodies beyond the orbit of Neptune. Less predictable are long-period comets, many of which arrive from a distant region called the Oort cloud about 100,000 astronomical units from the Sun. These comets can take as long as 30 million years to complete one trip around the Sun. As many as a trillion comets may reside in the Oort cloud, orbiting the Sun near the edge of the Sun's gravitational influence.
11Comet.png
# ASTEROIDS: over 90000 numbered
#  RADIUS: range from <1 to 1000 km
#  CONSTITUENTS: rock
#  MAIN LOCATION:  between Mars & Jupiter
# COMETS: perhaps trillions.
# : RADIUS: <1 to 300km
# : CONSTITUENTS: dust & frozen gases
# : MAIN LOCATION: Oort Cloud