Solar System Sun and Stars Planets Comets Asteroids

Sun: Our Nearest Star The Sun is our nearest star. A star is a ball of hot gases that pours out huge amounts of heat, light, and other energy. The Sun can hold a million Earths. If you could fly to the Sun, it would take 17 years. All life on Earth depends on the Sun.

Mercury: Sun’s Nearest Planet Mercury is the first planet from the Sun. Mercury is a swift little planet. Mercury is dry and hot. Its closeness to the Sun makes it difficult to study.

Venus: Hottest Planet The second planet from the Sun is Venus. Venus is hidden beneath deep, yellow sulfuric acid clouds. Venus’s air is mostly carbon dioxide (the air we breathe out). The thick air around Venus acts as a blanket and traps the heat. One of the largest craters in the Solar System is on Venus.

Earth: Watery Planet Earth is the only planet we know where life exists. Atmosphere around Earth is made of oxygen, nitrogen, carbon dioxide, and other gases. Earth revolves (circles) around the Sun once every 365 days (year). It also rotates (spins) on its axis once every 24 hours (day).

Moon: Our Rocky Neighbor Earth has one natural satellite, the Moon. The moon is an airless little world. It orbits (goes around) our planet once every month. The moon was bombarded by asteroids and so has a heavily-cratered surface. The first person to land on the Moon was Neil Armstrong.

Mars: Red Planet MARINER 4 and two Viking flights sent back close-up photographs of Mars. Mars is a little more than half Earth’s size. It takes Mars 2 years to orbit the Sun. Mars’ soil has a lot of iron oxide (rust) that gives it a red color. Mars has 2 moons.

Jupiter: King of the Planets Jupiter is the largest planet. It is the first of the 4 giant, gas outer planets. It has a well-known mark called the GREAT RED SPOT, which is 2 times the size of the U.S. It is an area of stormy winds. Jupiter has no surface. Spaceships cannot land on it. Jupiter has more than 17 moons (Ganymede is the largest moon in the Solar System.) Great Red Spot

Saturn: Planet with Ears Saturn was first seen by an Italian astronomer named Galileo. He said the planet had “ears.” Saturn’s rings are made of dust and ice. Jupiter is colorful, but scientists feel that Saturn is the most beautiful. Saturn has more moons than any other planet.

Uranus: Tipped-Over Planet In 1781 an astronomer saw a small spot that was gliding backward across the sky. He knew that stars do not move that way. He knew it must be a planet – Uranus. Like Jupiter and Saturn it is made of gas. It also has faint rings. It is tipped over on its side so that one pole faces the Sun giving it a day that lasts 42 Earth years. Uranus also has several moons.

Neptune: Last Giant Neptune wasn’t discovered until 1846. It was named for the Roman god of water. Even though it is the color of water, it is not made of water but of deadly gases like those found on Uranus. The Hubble telescope will help us study the far-out planets.

Pluto: Last Planet? It is the smallest and last known planet. Some astronomers think that it may not be a planet. Sometimes Pluto’s orbit crosses Neptune’s orbit. Then Neptune is the last planet. Pluto has one moon.

Asteroids asteroid Saturn

Comets