This is our solar system's Sun.  It is one of billions of stars in our galaxy.  It is the largest body in the solar system.  Over one million Earths could fit inside it!  It has a diameter of about 865,000 miles (1,392,000 km.)  It is massive compared to the planets which are all in orbit around it.  It is made up mostly of hydrogen.  Because of its mass and the great pressure generated by its gravity, it acts as an enormous nuclear fusion reactor converting its hydrogen into heleum.  This is what causes the Sun to be hot.  The Sun has a core temperature of 22.5 million degrees F (14 million degrees C) and a surface temperature of 9,932 degrees F (5,500 degrees C.)  The Sun is expected to remain hot for several billion more years.

      Mercury is the closest planet to the Sun.  It orbits the Sun at a distance of roughly 36,000,000 miles (58,000,000 km.)  It has a diameter of about 3,032 miles (4,878 km) which is 40% of the Earth's diameter.  It is only slightly larger than the Earth's Moon. Mercury has no moon of its own.  Mercury rotates on its axis once every 59 Earth days and completes an orbit around the Sun every 88 Earth days.  The combined effect of its rotation and orbit give Mercury a day of its own that is equal to 176 days on Earth.  The difference in temperature between day and night on Mercury is quite extreme.  Its daytime temperature can reach about 840 F (450 C.)  At night Mercury's temperature drops to about -275 F (-170 C.)  Small amounts of water ice are believed to be present at Mercury's poles.  Mercury has no atmosphere.  It has a gravity which is 38% of that on Earth.

     Venus is the second planet from the Sun.  It orbits the Sun once every 226 Earth days at a distance of about 67 million miles (108 million km) and rotates on its axis every 243 Earth days.  It has a diameter of about 7,522 miles (12,104 km.)  Venus has a temperature of about 891 degrees F (477 degrees C.)  It has a very thick and heavy atmosphere made mainly of carbon dioxide with about 3% nitrogen and clouds made of sulfuric acid.  Its gravity is 90% of the gravity on Earth.  Venus has no moon.

     Earth is the third planet from the sun and is our home.  It is a quite remarkable planet who's distance from the sun, temperate climate, abundant water, and oxygen rich atmosphere make it a perfect place for life to flourish.  Although future discoveries may change current knowledge, so far Earth is the only place in the universe where we are certain that life exists.  Because of Mankind's presence on the Earth, Earth is also unique because its surface has been altered not just by natural forces but also by human intellegence.  Man has added cities, towns, and roadways to its surface.  He has changed the course of rivers and turned countless square miles of wilderness into farmland.

     Earth is 93 million miles (149.6 million km) from the Sun and has a diameter of 7,927 miles (12.757 km.)  It rotates on its axis once every 23 hours and 56 minutes.  It revolves around the Sun in 365 days and 5 hours.  Its temperature ranges from -128 degrees to 136 degrees F (-89 degrees to 57.7 degrees C.)  It has an atmosphere which is about 78% nitrogen and 21% oxygen whith other trace gases.  It has one moon named the Moon.

     Mars is the fourth planet from the Sun.  It has a diameter of 4,217 miles (6,785 km.)  It has a rotation about its axis of 24.6 hours and completes an orbit about the Sun (one Martian year) in 1 Earth year and 321 Earth days.  It has a gravity which is 37% of Earth's gravity.  A 200 pound man on Earth would weigh about 74 pounds on Mars.  Temperatures on Mars range from about -200 degrees F to 32 degrees F (-129 degrees C to 0 degrees C.)  Mars has a thin atmosphere made up mostly of carbon dioxide. Mars has two moons which are named Deimos and Phobos.

     The landscape of Mars is largely rough and rocky.  It closely resembles the terrain of Arizona or Utah in the United States.

    The asteroid belt is a region in space located between the orbits of Mars and Jupiter.  It is populated by irregularly shaped rocks of various dimensions known as asteroids.  These rocks range in size from several hundred miles to theoretically the size of a grain of sand.  At least one one of these asteroids fits the definition of "dwarf planet."  That asteroid/dwarf planet is named Ceres.

     Ceres is a dwarf planet which orbits the Sun at a distance of about 257,500,000 miles ( between the orbit of Mars and the orbit of Jupiter.)  Ceres orbits the Sun once every 4.6 years and rotates on its axis once every nine hours.  Ceres resides within the asteroid belt and is the largest body within the belt.  Ceres' mass constitutes about 32% of the asteroid belt's total mass.  Generally speaking, asteroids are irregularly shaped and small in comparison to Ceres.  Ceres is spherical in shape and rather large with a diameter of 600 miles (966 km), distinguishing it from other bodies in the belt.  Ceres was discovered in 1801 by Giuseppe Piazzi and is named after Ceres the Roman goddess of motherly love.

     The asteroid pictured at right is named Vesta.  (Sorry for the out of focus picture.  Its the best that the Hubble telescope could come up with.)  It is the second largest object in the asteroid belt after the dwarf planet Ceres.  It has a diameter of about 329 miles (530 km) and constitutes about 9% of the mass of the asteroid belt.  It was discovered by the German astronomer Heinrich Olbers in 1807.  It is the brightest asteroid.  Other examples of asteroids in the asteroid belt are pictured below.  They are: Gaspra, Steins, Mathilde, and Ida.  They are but only a few of the many thousands of bodies thought to exist in the asteroid belt.  Gaspra is about 11.3 miles (18.2 km) across and was dicovered in 1916 by the Russian astonomer G. N. Neujmin.  Steins is about 3 miles (5 km) across and was discovered in 1969 by Nikolai Stepanovich Chernykh.  Mathilde is about 41 miles (66 km) across and was discovered in 1885 by Johann Palisa.  Palisa also discovered Ida a year earlier in 1884.  Ida is about 33.3 miles (53.6 km) across and was recently found to have a very tiny moon in orbit around it which has been named Dactyl.

     Jupiter is the fifth planet from the Sun.  It is the largest planet with a mass which is equal to two and a half times all the other planets combined.  Jupiter, Saturn, Uranus, and Neptune make up the gas giant planets which are often referred to as the Jovian planets.  Jupiter is named after the Roman god Jupiter.  Because of its rapid rotation, Jupiter has a noticable bulge at its eaquator.  Jupiter's surface clouds are segregated into bands which rotate about the planet at different speeds and even in different directions.  A prominent feature of Jupiter is its Great Red Spot, a giant storm, which is known to have existed for centuries.  Jupiter, like the other Jovian planets, has a planetary ring system.  Jupiter's ring, however, is thin and faintly visible which is in contrast to Saturn's rings which are quite prominent.  Jupiter orbits the Sun at a distance of about 484 million miles (779 million km.)  At this distance light from the Sun takes over 40 minutes to reach Jupiter.  Jupiter completes one orbit around the Sun in about 11.86 Earth years.  Jupiter's equator rotates about its axis once every 9.8 hours.  Jupiter's atmosphere is made up mostly of hydrogen but is also about 25% helium (by mass.)  Jupiter's temperature at the top of its clouds is about -101 F (-150 C.)  Jupiter has at least 63 moons.  The four largest moons were discovered by Galileo Galilei in 1610.  They are known as the Galilean moons.  Their names are Io, Europa, Ganymede, and Callisto.  They are pictured below.

     Saturn is the sixth planet from the Sun.  It is the second largest planet in the solar system after Jupiter.  It has a diameter of about 74,500 miles (119,871 km.)  Saturn is a gas giant and one of the four Jovian planets.  (See the article on Jupiter above.)  It is named after the Roman god Saturn.  Saturn orbits the Sun at an average distance of about 889 million miles (1.425 billion km.)  At this distance it takes light from the Sun one hour and fifteen minutes to reach Saturn.  It takes Saturn about 29.5 Earth years to complete one orbit.  It has an average rotation of about 10 hours and 33 minutes.  Like Jupiter, Saturn has a slight bulge about its equator due to its rapid rotation.  Saturn also has an atmosphere similar to Jupiter which is made up mostly of hydrogen with a lesser amount of helium.  Saturn experiences the fastest winds of all the planets in the solar system.  Its winds can reach over 1,000 miles (1,610 km) per hour.  The temperature at the top of Saturn's clouds is about -274 degrees F (-170 degrees C.)  Saturn has a surface gravity which is about nine tenths of the gravity on Earth.  Saturn has over sixty moons.  A few of its larger moons are pictured below.  Included is Titan, the largest moon in the solar system.

     Saturn is a truly magnificent planet to behold.  Its enormous size and majestic ring system make it a jewel in the inky blackness of space.

     Uranus is the seventh planet from the Sun.  It orbits the Sun at a distance of about 1.8 billion miles (2.9 billion km) and takes about 84.3 Earth years to complete one orbit.  It takes light from the Sun over two and a half hours to reach Uranus.  Uranus rotates about its axis once every 17 hours and 14 minutes.  Uranus is unique in our solar system in that it is tilted nearly sideways in relation to the other planets, with its rings appearing like a target's bullseye when viewed from Earth.  Uranus is the third largest planet with a diameter of about 32,000 miles (51,500 km) and is one of the solar system's four Jovian (Jupiter-like gas giant) planets.  Uranus has an atmosphere similar to Jupiter and Saturn in that it is composed mainly of hydrogen and helium but it also contains substantial  quantities of water, amonia, and methane ice.  Uranus has the coldest atmosphere of all the planets with an upper cloud temperature of -328 degrees F (-200 degrees C.)  Wind speeds on Uranus can reach up to 560 mph (900 km/h.)  Uranus has a gravity which is nine tenths the gravity on Earth.  Uranus has 27 known moons.  Some of those moons are pictured below.

     Neptune is the eighth planet from the Sun and orbits the Sun at a distance of about 2.795 billion miles (4.5 billion km.)  At this distance it takes light from the Sun over four hours to reach Neptune!  It takes Neptune about 165 Earth years to complete one orbit about the Sun.  Neptune rotates on its axis once every 17.24 hours.  Neptune is the fourth largest planet in the solar system and is one of the four gas giants, but like Uranus its atmosphere contains water, amonia, and methane ices.  Because of this, Neptune and Uranus are sometimes refered to as the "ice planets."  Neptune has a gravity which is 112% of the gravity on Earth.  A person weighing 150 pounds on Earth would weigh about 168 pounds on Neptune.  Neptune has 13 known moons.  There are images of two of them below.

    The Kuiper Belt lies beyond Neptune and is similar to the Asteroid Belt but is much more massive.  It is different from the Asteroid Belt in that the Asteroid Belt is composed of rock and metal but the Kuiper Belt is composed of frozen ices such as methane, amonia, and water.  The Kuiper Belt contains many objects which are over 100 km in diameter.  Three dwarf planets reside in the Kuiper Belt.  These are Pluto, Haumea, and Makemake.

     Pluto was formerly classified as the ninth planet from the Sun but has been reclassified as a dwarf planet.  It has a diameter of 1,456 miles (2,344 km.)  Pluto orbits the Sun at a distance of about 3.67 billion miles (5.91 billion km) and takes 248 Earth years to complete one orbit.  Light from the Sun takes more than five hours to reach Pluto.  Pluto rotates on its axis once every 6.387 Earth days.  The temperature on Pluto ranges from     -387 to -369 degrees F (-233 to -223 degrees C.)  Pluto is so far from the Sun that the coldness of space usually prevents it from having an atmosphere.  However, there are times when Pluto is closer to the Sun than other times and when this happens Pluto warms up slightly and a thin atmosphere forms.  This atmosphere is made up mostly of nitrogen with small amounts of carbon monoxide and methane.  Pluto has a gravity which is about six percent as strong as Earth's.  Pluto has three moons.  The largest moon is named Charon.  The other two moons are called Nix and Hydra.

     Haumea is a dwarf planet located in the Kuiper belt along with Pluto and Makemake.  Haumea orbits the Sun at a distance of about 4.03 billion miles (6.48 billion km.)  It completes one orbit every 285 Earth years.  Haumea rotates once every four hours.  Because of its rapid rotation it has acquired a strange, ellipsoid shape.  Haumea is about 1,218 miles (1,960 km) across in its longest direction.  It is so far from the Sun that it takes light from the Sun almost six hours to reach Haumea.  It has two moons named Hi'iaka and Namaka.

     Makemake is a dwarf planet located in the Kuiper belt along with Pluto and Haumea.  It was discovered in 2005 by a team headed by Mike Brown.  It has a diameter of about 1,000 miles (1,609 km.)  Makemake orbits the Sun at a distance of about 4.25 billion miles (6.84 billion km.)  Makemake makes one revolution about the Sun every 310 Earth years.  Is period of rotation is not known.  It takes light from the Sun over six hours to reach Makemake.  Makemake has no moons.

     The Scattered Disc is the most distant region of the known Solar System.  It lies beyond the Kuiper Belt and consists of objects whose orbits are effected by the gravities of the outer planets.  At least one dwarf planet resides in the Scattered Disk.  The name of that dwarf planet is Eris.

       Eris is a dwarf planet located in a region of the solar system known as the scattered disk.  This region lies beyond the Kuiper belt.  The dwarf planet Eris orbits the Sun at a distance of about 6.29 billion miles (10.12 billion km.)  Eris has a diameter of about 1,553 miles (2,500 km.)  It revolves around the Sun once every 557 Earth years.  Light from the Sun takes about nine hours to reach Eris.  Eris has one moon named Dysnomia.  Both Eris and Dysnomia are pictured at left.

     Comets orbit the Sun in highly elongated eliptical orbits which stretch from the outer regions of the Solar System to within the orbits of the inner planets.  They are composed of ice and dust which is warmed by the Sun as they draw near to it.  The ice and dust is then dispersed into space by the Sun's solar wind leaving a "tail" (actually a trail of debris) behind the comet.  Comets are believed to originate in the Scattered Disk.  Because their eccentric orbits are so large, comets generally make a brief but spectacular appearence in Earth's neighborhood only to quickly exit and not return again for many decades.