Sun & Planet Facts

The Solar System is comprised of one star-the Sun, eight known planets, the newly classified "dwarf planets", thousands of asteroids, comets, and meteoroids. There are many web sites that will provide you with very detailed information concerning all of these subjects. Here we provide you with some basic statistics to get you started.

Page Index: Sun / Mercury / Venus / Earth / Moon/ Mars / Asteroids / Jupiter / Saturn / Uranus / Neptune / Pluto / Quaoar & the Kuiper Belt / Comets / Sedna / Eris

What is a Planet? This question was officially answered in August 2006 by the International Astronomical Union, a world-wide group of astronomers who are the accepted sanctioning body for naming and classifying objects discovered in space. They offically defined a planet as any object that orbits a star, is large enough to be round, and has enough gravity to clear its orbit of smaller debris.

What is a "Dwarf Planet?" The IAU also created a new classification of solar system objects known as "Dwarf Planets", these would be objects that orbit a star, are large enough to be round, but not have enough mass (and therefore gravity) to clear its orbit of debris.

Under the new guidelines, Pluto is no longer a planet, instead it falls into the category of being a Dwarf Planet because it lies within the Kuiper Belt of thousands of icy asteroid like objects. Other solar system objects that are likely to fall into this new category might be Ceres (the largest asteroid), Quaoar, Sedna, and Eris formerly known as 2003UB313 (Xena).

For more information regarding this new classification system check out the following links:

SUN Rotates: 26 days. Surface Temp: 12,000°F (6000°C) Core Temp: 27 Million°F (15 Million°C) Diameter: 865,000 mi. (1,395,161 km). Density: 1.41. Mass=333,000 Earths. A middle aged (4.5 Billion yrs. old) average sized star. It's outer atmosphere "the heliosphere" extends beyond Pluto.

 Solar System Index / Northern Stars Explorations Page

MERCURY Rotates: 58 days 16 hours. Revolves: 88 days. High Temperature: 700°F (350°C) Low Temperature: -270° F (-170° C). Diameter: 3,031 miles. (4,878 km.) Density: 5.4. Mass=0.06 Earths. Gravity: 0.38 X Earth's. No moons or rings. Mercury was visited in 1974 by the Mariner 10 Space Probe and about 45% of the planets surface was photographed. It's surface is dominated by impact craters. The largest crater is called the Caloris Basin which measures 810 miles (1,300 km) in diameter. Lacking in mountains, Mercury's other dominant type of feature are scarps. Scarps are long cliffs formed by a contracting crust when the planet cooled. The largest scarp is called "Discovery Rupes" and is about 310 miles (500 km) long and about 2 miles (3 km) high. Solar System Index / Northern Stars Explorations Page

VENUS Rotates: 243 days. Revolves: 224.7 days. Average Temperature: 900°F (480°C) Diameter: 7,541 miles. (12,104 km.) Density: 5.2. Mass=0.8 Earths. Gravity: 0.9 X Earth's. Thick Carbon Dioxide (CO2) atmosphere. No Moons or rings. Venus has clouds of sulfuric acid. It has nearly 90 times more atmosphere than Earth. Named after the Roman Goddess of Love and Beauty. It is believed that it may rain sulfuric acid on Venus, but due to the high temperatures the rain evaporates before reaching the surface. Solar System Index / Northern Stars Explorations Page

Off Site Venus Links:

The Nine Planets / Magellan Probe

EARTH Rotates: 23 hours. 56 minutes. Revolves: 365.25 days. High Temperature: 130°F (58°C) Low Temperature: -126°F (-88°C). Gravity: 1 X Earth's. Diameter: 7,927 miles. (12,756 km.) Density: 5.5. Mass=1 Earth. Nitrogen & Oxygen atmosphere. 1 moon, no rings. Earth is dominated by water which covers three quarters of it's surface area.

Solar System Index / Northern Stars Explorations Page

THE MOON Rotates:27 days, 8 hours. Revolves: 27 days, 7 hours. 43 minutes. (when measured in relationship to the stars) or 29 days, 12 hours. 44 minutes. (when measured in relationship to the Earth and Sun--this is the amount of time from one full moon to the next). High Temperature: 214°F (101°C) Low Temperature: -300°F (-184°C). The poles seem to have a near constant temperature of -140°F (-96°C). Diameter: 2,155 miles (3476 km). Density: 3.34. Evidence of water ice has been found deep in some craters near the moon's poles. Twelve astronauts have walked on the moon's surface between 1969 and 1972. Solar System Index / Northern Stars Explorations Page

Off Site Moon Links:

Apollo 11 / Clementine Probe / Lunar Prospector / The Nine Planets
Google Moon / Inconstant Moon

MARS Rotates: 24 hours. 37 minutes. Revolves: 1,88 years. High Temperature: 80°F (27°C). Low Temperature: -190°F (-123°C). Diameter: 4,197 miles. (6,794 km). Density: 3.9. Mass=0.1 Earths. Gravity: 0.38 X Earth's. Thin Carbon Dioxide atmosphere. 2 moons, no rings. In 1996 scientist found possible evidence of fossilized bacteria in a meteorite believed to have originated on Mars--perhaps long ago Mars had life! Mars has a canyon named Valles Marineras that would stretch from Maine to California if it were found on Earth. It also has the largest and tallest volcanoes in the solar system. Solar System Index / Northern Stars Explorations Page

Off Site Mars Links:

Mars Exploration (all active probes) / Mars Rovers
Mars Pathfinder / Mars Global Surveyor
Hubble Space Telescope Pictures / The Nine Planets
Mars Odyssey / Mars Express / Mars Reconnaissance

Have a rock from your hometown examined by a scientist using the same tools that Spirit and Opportunity use to examine rocks on Mars!

ASTEROIDS Between Mars and Jupiter is a region of the solar system known as the asteroid belt. Thousands of asteroids have been catalogued. The asteroid pictured here, named Gaspra, was the first asteroid seen up close by a space probe, the Galileo Probe to be exact.

Solar System Index / Northern Stars Explorations Page

JUPITER Rotates: 9 hours. 48 minutes. Revolves: 11.86 years. Cloud top Temperature: -140°F (-95°C) Diameter: 88,733 miles. (142,796 km.). Density: 1.3. Mass=318 Earths. Gravity: 3 X Earth's. Composition: Mostly Hydrogen, Helium. 63 moons, 1 small ring. Jupiter has a huge storm called the Great Red Spot that has been blowing about on Jupiter for hundreds of years. In 1994 Jupiter was hit by Comet Shoemaker-Levy 9.

Solar System Index / Northern Stars Explorations Page

SATURN Rotates: 10 hours. 39 minutes. Revolves: 29.46 years. Cloud top Temperature: -292°F (-180°C) Diameter: 74,600 miles. (120,000 km.). Density: 0.7. Mass=95 Earths. Gravity: 1.32 X Earth's. Composition: Mostly Hydrogen, Helium. 56 moons. It has a large ring system.

 Solar System Index / Northern Stars Explorations Page

URANUS Rotates: 16 hours. 48 minutes. Revolves: 84 years. Cloud top Temperature: -346°F (-210°C). Diameter: 31,600 miles. ((50,800 km.). Density: 1.3 Mass=14.5 Earths. Gravity: 0.93 X Earth's. Composition: Mostly Hydrogen, Helium, some ammonia, methane. 27 moons, about a dozen thin rings. Uranus is tipped on its side by 98°.

Solar System Index / Northern Stars Explorations Page

NEPTUNE Rotates: 16 hours 3 minutes. Revolves: 164.8 years. Cloud top Temperature: -364°F (-220°C). Diameter: 30,200 miles. (48,600 km.). Density: 1.6 Mass=17 Earths. Gravity: 1.23 X Earth's. Composition: Mostly Hydrogen, Helium, some methane and ammonia. 13 moons, 3 thin rings, 2 broad rings.

Solar System Index / Northern Stars Explorations Page

PLUTO Rotates: 6 days, 9 hours. Revolves: 248 years. Temperature: -400°F (-238°C). Diameter: 1900 mi. (3,000 km.). Density: 2. Mass=0.002 Earths. Gravity: 0.03 X Earth's. Has a very thin atmosphere. 3 moons, no rings. The largest moon, Charon, is half the size of Pluto, some scientists refer to Pluto & Charon as a "Double Planet." Pluto's orbit is very elliptical and tilted; it actually crosses inside Neptune's orbit from 1979-1999.

Pluto was officially reclassified in August 2006 as no longer an official planet, instead it joins the ranks of dwarf planets

Solar System Index / Northern Stars Explorations Page

Off Site Pluto Links:

Hubble Space Telescope Pictures / New Horizons Probe / The Nine Planets

QUAOAR & THE KUIPER BELT Quaoar is approximately 800 miles in diameter and is slightly farther away from the Sun than Pluto. It is made primarily of ices. It is the largest known object in the Kuiper Belt (other than Pluto!). The Kuiper Belt is a band of icy objects just beyond the orbit of Neptune; similar to the Asteroid Belt, the Kuiper Belt is made of objects too small to be labelled as planets. Both Quaoar and Pluto reside within the Kuiper Belt.

Solar System Index / Northern Stars Explorations Page

Off Site Quaoar Links:

Quaoar--Cal Tech

ERIS (formerly known as 2003 UB 313 or Xena) was first photographed in October 2003, but was not detected until January 2005. Its discovery was announced in August 2005. This object is larger than Pluto and currently about three times farther away from the Sun than Pluto. It may soon be officially classified as the 10th planet. It does not yet have an official name, that will come soon. It is made of ices, much like Pluto. It takes this new planet 557 years to orbit the Sun just once. Its orbit is tilted nearly 45 degrees up at an angle compared to the plane of Earth's orbit. Recently scientists announced the discovery of a moon orbiting Xena, it has been nicknamed "Gabrielle."

Solar System Index / Northern Stars Explorations Page

SEDNA Sedna is the most distant object yet discovered in the solar system. It was discovered in 2003. It is roughly three tumes further away than Pluto, well outside the Kuiper Belt. It is approximately 1000 miles in diameter and takes nearly 10,500 years to go around the sun just once. Currently, scientists have not officially classified it as the tenth planet, if that does happen, Sedna would become the smallest planet, the coldest planet, and the most distant planet! Sedna was named after an Inuit Goddess of the Sea.

Solar System Index / Northern Stars Explorations Page

Off Site Sedna Links:

Sedna--Cal Tech / The Nine Planets

COMETS Comets are comprised of a ball of ice, snow, rocks, and pebbles that orbit the Sun in highly elliptical (oval) orbits. The "dirty snowball" can vary in size from a couple of miles in diameter to perhaps 25 or 30 miles in diameter. The Sun's radiation and solar wind melts the outer layers of icy materials to form the "Coma" which is sort of like a fog bank that engulfs the nucleus (snowball). The coma might be as much as 100,000 miles in diameter. The coma is then pushed away from the sun by the solar wind to form the comet's tail. Comets have two basic tails, an Ion or Gas Tail and a Dust Tail.

Solar System Index / Northern Stars Explorations Page

Off Site Comet Links:

Comet Observation Page / Comet Shoemaker Levy 9 Impacts Jupiter /

StarDust Probe to a Comet / Deep Impact Probe / Rosetta Mission

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METEOR SHOWERS are covered on their own page.

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Off Site Solar System Links that will provide you with good basic information:

Astronomical Society of the Pacific / Astronomy / The Jet Propulsion Laboratory /
NASA / The Nine Planets / The Planetary Society / Sky and Telescope / The Solar System Live /
National Geographic's Virtual Solar System / Merlot

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