Solar System Facts


















8 Planets?

Off Site Links


Scrolling Through the Solar System
Check out an on-line distance scale of the planets.

The Solar System Song
by Ms. Poland's Class January 2008, Jordan Acres School, Brunswick, Maine


SunSUN Rotates: 26 days. Surface Temp: 12,000F (6000C) Core Temp: 27 MillionF (15 MillionC) 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. Its outer atmosphere "the heliosphere" extends beyond Pluto.


Off Site Sun Links:
The Sun / SOHO / Ulysses Probe to the Sun / Genesis Mission
The Virtual Sun


MercuryMERCURY Rotates: 58 days 16 hours. Revolves: 88 days. High Temperature: 700F (350C) 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.
Off Site Mercury Links:

Messenger Space Probe


VenusVENUS Rotates: 243 days. Revolves: 224.7 days. Average Temperature: 900F (480C) 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.
Off Site Venus Links:

Magellan Probe


EARTH Rotates: 23 hours. 56 minutes. Revolves: 365.25 days. High Temperature: 130F (58C) Low Temperature: -126F (-88C). 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 its surface area.
Off Site Earth Links:

The Aurora Page / Terra Server


MoonTHE 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: 214F (101C) Low Temperature: -300F (-184C). The poles seem to have a near constant temperature of -140F (-96C). 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.
Off Site Moon Links:

Apollo 11 / Clementine Probe / Lunar Prospector
Google Moon / Inconstant Moon


MarsMARS Rotates: 24 hours. 37 minutes. Revolves: 1,88 years. High Temperature: 80F (27C). Low Temperature: -190F (-123C). 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.
Off Site Mars Links:

Mars Exploration (all active probes) / Mars Rovers
Mars Pathfinder / Mars Global Surveyor
Mars Odyssey / Mars Express / Mars Reconnaissance / Mars Phoenix
Spirit and Opportunity Curiosity Rover (NASA) Curiosity Rover (JPL)


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.
Off Site Asteroid Links:
/ /
Malin Space Science System's NEAR Page / Near Shoemaker Probe
Muses-C Mission


JupiterJUPITER Rotates: 9 hours. 48 minutes. Revolves: 11.86 years. Cloud top Temperature: -140F (-95C) Diameter: 88,733 miles. (142,796 km.). Density: 1.3. Mass=318 Earths. Gravity: 3 X Earth's. Composition: Mostly Hydrogen, Helium. 67 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.
Off Site Jupiter Links:

Comet Shoemaker Levy 9 Impacts Jupiter /

Galileo Probe / Galileo Fun Stuff /



SaturnSATURN Rotates: 10 hours. 39 minutes. Revolves: 29.46 years. Cloud top Temperature: -292F (-180C) Diameter: 74,600 miles. (120,000 km.). Density: 0.7. Mass=95 Earths. Gravity: 1.32 X Earth's. Composition: Mostly Hydrogen, Helium. 62 moons. It has a large ring system.
Off Site Saturn Links:

Cassini-Huygens ...... Voyager


UranusURANUS Rotates: 16 hours. 48 minutes. Revolves: 84 years. Cloud top Temperature: -346F (-210C). 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.
Off Site Uranus Links:



NeptuneNEPTUNE Rotates: 16 hours 3 minutes. Revolves: 164.8 years. Cloud top Temperature: -364F (-220C). 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. 14 moons, 3 thin rings, 2 broad rings.
Off Site Neptune Links:



PlutoPLUTO Rotates: 6 days, 9 hours. Revolves: 248 years. Temperature: -390F (-230C). Diameter: 1430 mi. (2,302 km.). Density: 2. Mass=0.002 Earths. Gravity: 0.03 X Earth's. Has a very thin atmosphere. 5 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 crossed 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.

Off Site Pluto Links:

New Horizons Probe


QuaoarQUAOAR Quaoar is approximately 800 miles in diameter and is slightly farther away from the Sun than Pluto. It is made primarily of ices.

Off Site Quaoar Links:

Quaoar--Cal Tech


MAKEMAKE (pronounced MAH-keh MAH-keh) Diameter: 950 mi. (1500 km.), it's the third largest Trans-Neptunian Object after Eris and Pluto. Originally designated 2005 FY9, Makemake was discovered on March 31, 2005, near Easter, hence its original knickname of "Easter Bunny". Since Kuiper Belt objects are all officially named after creation gods, 2005FY9 was named Makemake for the creation god found in the traditional mythology of Rapa Nui or Easter Island.


2003UB313ERIS (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 slightly smaller than Pluto and currently about three times farther away from the Sun than Pluto.. 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. Eris has one known moon, Dysnomia
Off Site Eris Links:

2003UB313--Cal Tech / NASA Tenth Planet?


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 Sedna as either a planet nor a dwarf planet, Sedna was named after an Inuit Goddess of the Sea.
Off Site Sedna Links:

Sedna--Cal Tech


Comet Hale BoppCOMETS 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.
Off Site Comet Links:

Comet Observation Page / Comet Shoemaker Levy 9 Impacts Jupiter /

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

Only 8 Planets? What Happened to Pluto?

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 fall into this new category are Ceres (the largest asteroid), Eris, and Makemake.

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

International Astronomical Union 2006 Resolutions / Tne Nine Planets

IAU Planet Definition pdf

Off Site Links:


The Jet Propulsion Laboratory

JPL Solar System Page

Hubble Space Telescope

Hubble Space Telescope Pictures


Sky and Telescope

NASA Solar System Exploration

Start Local: The Solar System

The Solar System Live

The Planetary Society

Astronomical Society of the Pacific

National Geographic's Virtual Solar System

NASA Tenth Planet?


Online Schools: Space and Science Online Study Guide for Kids


Northern Stars Planetarium and Educational Services
Fairfield, ME 04937
(207) 453-7668