Notes

Outline

The Nine Planets

The Nine Planets Can you name all nine planets?

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Mercury Mercury is the planet closest to our Sun, and it is the eighth largest of the nine planets. Mercury is a small, rocky planet - much like our Moon. It is covered with craters and has changed very little from when it was first formed. It rotates around the sun in about 88 days. The same side always faces the sun so it doesn’t see the light of day. The dark side is extremely cold. One of Mercury's largest features is called the Caloris Basin. It is about 1300 km across! It was probably created by a very large crash early in the history of the Solar System.

Venus Venus is the second planet from the Sun, and the sixth largest of all the nine planets. Venus' hot temperature is due to what we call "the Greenhouse Effect." The large amount of carbon dioxide in Venus' atmosphere acts like a blanket. The heat gets trapped underneath the thick layer of clouds. Because the heat has nowhere to go, Venus gets hotter and stays hot.

Venus Video This is an artists idea of what the surface of Venus might be like. No one has actually ever been to Venus but NASA has sent probes to study the planet.

Earth The Earth is a small, rocky planet which supports a variety of life. As far as we know, Earth is unique from all other planets in this respect. The Earth moves around the sun, taking one year to go around once. The moon goes around the Earth. It is smaller than the sun, but it looks as big as the sun because it is much closer to us.

Earth’s Moon The moon is roughly one sixth the size of Earth. It rotates around Earth every twenty-seven days, seven hours, and forty-three minutes. However, we only see one side of it because the other side never faces the Earth. Several Americans have walked on the moon as part of the Apollo space program. This is a look at the liftoff of Apollo 12 on November 14, 1969.

Moon Picture This picture shows you how the size of the earth compares to the size of the moon.

Astronauts left the American flag on the moon.

Apollo 12 Liftoff

Mars Mars is a small, rocky planet. There are no seas and it is always very cold.  The air is so thin that we could not breath it. It is smaller than the Earth, though bigger than our moon. Mars has permanent ice caps at both poles made up mostly of solid carbon dioxide. We know this as "dry ice." Very strong winds and vast dust storms sometimes blow through the entire planet for months! Mars has two tiny moons which orbit very close to the surface. Their names are Phobos and Deimos.

Mars’ Moon Deimos

Jupiter Jupiter is the fifth planet from the Sun and by far the largest of all nine planets. Jupiter is not like Earth. It is made up of gases, so we could never land a rocket there. Jupiter's most outstanding and interesting feature is called "The Great Red Spot", which is a huge storm in Jupiter's gas.

Jupiter Jupiter has sixteen moons.  Four of them are big.  One of them, called Io, has active volcanoes on it. You can see these four moons with any telescope. Jupiter has faint rings like Saturn's, but much smaller.  Unlike Saturn's, Jupiter's rings are dark . They're probably composed of very small grains of rocky material.

Jupiter’s Great Red Spot This is the huge storm that has been going for decades.

Jupiter’s Moon Io This is Jupiter’s moon Io. The bright light on the left of the picture is an erupting volcano. Io is the most volcanically active place in the solar system.

Jupiter’s Rings Jupiter has very faint rings.  They are much more difficult to see than the rings of Saturn.

Saturn Saturn is the sixth planet from the Sun, and the second largest of the nine planets. Like Jupiter, Saturn has a surface made up of gas. Saturn has rings around it, which are made of little bits of ice moving around Saturn.  Saturn has eighteen moons that we know of.

Uranus Uranus is a cold, giant gas planet which is made up of mostly rock and various ices. Uranus has a faint ring system and 21 known moons. Uranus is a very odd planet. It sits on its side with the north and south poles sticking out the sides.

Moons of Uranus This picture shows Uranus with four of its moons.

Neptune Neptune is a cold, giant gas planet which is made up of mostly rock and various ices. Neptune is about half as big as Saturn and has eight known moons; seven small ones and a large moon called Triton. Neptune is usually the eighth planet from the Sun but occasionally the ninth planet Pluto crosses Neptune's orbit and becomes the "eighth planet". Its bluish color comes from its atmosphere of methane gas.

Neptune’s Moon Triton

Pluto Pluto is the farthest planet from the Sun (usually) and by far the smallest of the nine planets. Discovered in 1930, Pluto has always appeared as nothing more than a dot of light in even the largest earth-based telescopes.   The Hubble Space Telescope is able to get better images of this distant planet. Pluto is 2/3 the size of Earth's Moon but 1,200 times farther away. Viewing surface detail is as difficult as trying to read the printing on a golf ball located thirty-three miles away!

Pluto’s Size This shows Pluto on the left and its moon Chiron on the right.  By comparing them to the map of the United States, you can see how small they are.

The following slides show additional pictures for each planet.  There are links to them on the planet slides.

Mercury’s Caloris Basin About 4 billion years ago, a 100 kilometer-wide asteroid struck Mercury creating an impact crater that is 1300 kilometers wide. The Caloris Basin, as the crater is called, could hold the entire state of Texas!

Mercury Formation

Mercury Formation 2

Mercury Picture

The Greenhouse Effect The greenhouse effect is the term used to describe the way a planet’s atmosphere traps heat and warms a planet. The sun’s  energy passes through the atmosphere and heats up the surface of the planet.  Some of that heat is trapped by gasses in the air such as carbon dioxide.

Mercury Facts Average Distance From Sun Kilometers: 57,000,000 Miles: 36,000,000 Astronomical Units: 0.387 Length of Year: 87.97 days Length of Day: 58 days 15 hours 30 minutes Average Orbital Speed Kilometers/Second: 47.89 Miles/Second: 29.76 Equatorial Diameter Kilometers: 4,878 Miles: 3,031 Earth=1: 0.382 Mass (Earth=1): 0.056 Volume (Earth=1): 0.056 Number of Known Satellites: 0

Venus Facts Average Distance From Sun Kilometers: 108,200,000 Miles: 67,000,000 Astronomical Units: 0.723 Length of Year: 224.7 days Length of Day: 243 days 0 hours 25 minutes (Retrograde) Average Orbital Speed Kilometers/Second: 35.03 Miles/Second: 21.77 Equatorial Diameter Kilometers: 12,100 Miles: 7,518 Earth=1: 0.949 Mass (Earth=1): 0.815 Volume (Earth=1): 0.855 Number of Known Satellites: 0

Earth Facts Average Distance From Sun Kilometers: 149,600,000 Miles: 93,000,000 Astronomical Units: 1.000 Length of Year: 365.26 days Length of Day: 23 hours 56 minutes 4 seconds Average Orbital Speed Kilometers/Second: 29.79 Miles/Second: 18.51 Equatorial Diameter Kilometers: 12,756 Miles: 7,926 Earth=1: 1.000 Mass (Earth=1): 1.000 Volume (Earth=1): 1.000 Number of Known Satellites: 1

Moon Facts Average Distance From Earth Kilometers: 384,500 Miles: 238,900 Astronomical Units: 0.0026 Length of Year (To Orbit Earth): 27.32 days Length of Day: 27 days 7 hours 43 minutes Average Orbital Speed Kilometers/Second: 1.023 Miles/Second: 0.636 Equatorial Diameter Kilometers: 3,476 Miles: 2,160 Earth=1: 0.24 Mass (Earth=1): 0.012 Volume (Earth=1): 0.020

Mars Facts Average Distance From Sun Kilometers: 227,900,000 Miles: 141,600,000 Astronomical Units: 1.524 Length of Year: 1.88 years Length of Day: 24 hours 37 minutes 12 seconds Average Orbital Speed Kilometers/Second: 24.13 Miles/Second: 14.99 Equatorial Diameter Kilometers: 6,796 Miles: 4,223 Earth=1: 0.532 Mass (Earth=1): 0.107 Volume (Earth=1): 0.151 Number of Known Satellites: 2

Jupiter Facts Average Distance From Sun Kilometers: 778,300,000 Miles: 483,600,000 Astronomical Units: 5.203 Length of Year: 11.86 years Length of Day: 9 hours 50 minutes 33 seconds (at equator) Average Orbital Speed Kilometers/Second: 13.06 Miles/Second: 8.12 Equatorial Diameter Kilometers: 143,000 Miles: 89,353 Earth=1: 11.27 Mass (Earth=1): 317.89 Volume (Earth=1): 1,403 Number of Known Satellites: 27 (plus rings)

Saturn Facts Average Distance From Sun Kilometers: 1,427,000,000 Miles: 886,700,000 Astronomical Units: 9.539 Length of Year: 29.46 years Length of Day: 10 hours 39 minutes 24 seconds (at equator) Average Orbital Speed Kilometers/Seconds: 9.64 Miles/Second: 5.99 Equatorial Diameter Kilometers: 120,000 Miles: 74,565 Earth=1: 9.44 Mass (Earth=1): 95.15 Volume (Earth=1): 833 Number of Known Satellites: 22 (plus rings)

Uranus Facts Average Distance From Sun Kilometers: 2,870,000,000 Miles: 1,783,000,000 Astronomical Units: 19.18 Length of Year: 84.01 years Length of Day: 17 hours 14 minutes ? seconds (Retrograde) Average Orbital Speed Kilometers: 6.81 Miles: 4.23 Equatorial Diameter Kilometers: 50,800 Miles: 31,600 Earth=1: 4.10 Mass (Earth=1): 14.54 Volume (Earth=1): 63.0 Number of Known Satellites: 21 (plus rings)

Neptune Facts Average Distance From Sun Kilometers: 4,497,000,000 Miles: 2,794,000,000 Astronomical Units: 30.06 Length of Year: 164.8 years Length of Day: 18 hours 25 minutes 55 seconds Average Orbital Speed Kilometers/Second: 5.43 Miles/Second: 3.37 Equatorial Diameter Kilometers: 49,500 Miles: 30,758 Earth=1: 3.88 Mass (Earth=1): 17.23 Volume (Earth=1): 55.3 Number of Known Satellites: 8 (rings)

Pluto Facts Average Distance From Sun Kilometers: 5,913,520,000 Miles: 3,666,000,000 Astronomical Units: 39.44 Length of Year: 248.54 years Length of Day: 6 days 9 hours 17 minutes Average Orbital Velocity Kilometers/Second: 4.74 Miles/Second: 2.95 Equatorial Diameter Kilometers: 2,294 Miles: 1,425 Earth=1: 0.18 Mass (Earth=1): 0.0022 Volume (Earth=1): 0.013? Number of Known Satellites: 1

Credits Facts Slides: Bell , Richard S. . "The Solar System." Stargazer Online. <http://my.voyager.net/stargazer/solar_system.html>. Text: Smith, Gail . "The Planets." The Planets of Our Solar System. <http://scils.rutgers.edu/~gails/planets.html>. Windows to the Universe. University Corporation for Atmospheric Research. <http://www.windows.ucar.edu/>. All pictures are believed to by public domain.