Solar System Background Information

Space is a subject that engages children and encourages them to ask questions about the world around them. Through learning about our Solar System, children can apply and build on concepts they have already learned and develop an understanding of the vast world beyond our planet. We recommend screening the movies on the Moon and Earth and completing the accompanying features and activities before diving into the Solar System topic.

Remind children that our Solar System is a group of planets, moons, and other bodies that orbit, or go around, the Sun. Celestial bodies include comets and asteroids. It is important to note that a solar system is a group of bodies that orbit a star. In our Solar System, the Sun is the star at the center of our Solar System and bodies orbit around it. A star is a body of hot gases that makes its own light and heat. The center of the Sun is about twenty-seven million degrees Fahrenheit, or about fifteen million degrees Celsius. The diameter of the Sun is about 1.4 million kilometers, or roughly 870,000 miles. About 109 Earths can fit across the Sun. Despite its large size, the Sun is actually a medium-sized star. There are many stars that are significantly larger. Even though the Sun is millions of miles away from Earth, it is the closest star to our planet. The Sun provides heat and light and enables living things to survive.

The Solar System is divided into two main sections. The inner Solar System contains four planets, Mercury, Venus, Earth, and Mars. The planets of the inner Solar System are considered terrestrial, which means they are rocky. Many have craters, ridges, and volcanoes.

Mercury is the planet closest to the Sun. It rotates slowly, taking about fifty-eight Earth days to rotate. It takes nearly eighty-eight Earth days for Mercury to complete its orbit around the Sun. The side of Mercury that faces the Sun is extremely hot, while the side facing away is extremely cold. Temperatures on the planet can range from -183 degrees Celsius to 427 degrees Celsius.

Venus is the second planet from the Sun. Its size is similar to that of Earth and thus it is often called Earth’s “sister planet.” Venus’s atmosphere is made mostly of carbon dioxide and its clouds trap in heat, much like the greenhouse effect. Venus is the hottest of all the planets with surface temperatures reaching up to 460 degrees Celsius. All the planets of our Solar System rotate counter-clockwise, from west to east, except for Venus and Uranus. Scientists believe Venus rotates backwards because an asteroid collided with it long ago and disturbed its rotation.

Earth is the only planet where scientists have found life so far. It is known as the “blue planet” due to the presence of water which covers about 70% of its surface. Children can learn more about our planet by exploring our Earth movie.

Mars is known as the “red planet” due to the reddish color of its rocks. For years, scientists believed the planet was once covered by liquid water, and in July of 2008, ice was discovered by the Phoenix Mars Lander.

The outer Solar System contains the gas giants, which are large planets made mostly of gases. Jupiter, Saturn, Uranus, and Neptune are the gas giants of the outer Solar System. Jupiter is the largest of all the planets, and it is composed mostly of hydrogen. Scientists have discovered over sixty moons that orbit the planet and there is also a faint ring that circles the planet. There is a permanent storm on the planet called the Great Red Spot, which you can see in images of the planet. Scientists believe that this storm has lasted well over three hundred years.

Saturn is the second largest planet, and it is most recognizable by its rings, which are made of ice, rocks, and dust. Like Jupiter, Saturn is composed mostly of hydrogen. There are sixty known moons that orbit Saturn and one of them, Rhea, may have rings. This would be the first discovery of a moon that has a ring system.

Uranus and Neptune are sometimes considered “ice giants” because their composition differs from Jupiter and Saturn. While the atmospheres of both Uranus and Neptune are comprised mostly of hydrogen and helium, there is also the presence of ice and frozen volatile gases such as ammonia and methane. Uranus is the coldest planet in our Solar System, with temperatures reaching -224 degrees Celsius. Uranus also has a faint ring system. The most notable feature of Uranus is its axis of rotation. While most planets spin like a top, Uranus spins on its side, much like a rolling ball. Therefore, the poles of Uranus are located where most planets have their equators. Many scientists hypothesize that a planet may have knocked Uranus off its axis soon after it was formed.

Neptune is the farthest planet from the Sun, and is similar in size and composition to Uranus. Neptune’s striking blue color is most likely from the presence of methane in its atmosphere. Like Jupiter, Neptune has a permanent storm, called the Great Dark Spot. Neptune also has a ring system which is composed mostly of ice. It is important for your children to understand that many of the planets, and not just Saturn, have rings. In fact, all the gas giants (including the ice giants) have rings.

For decades, Pluto was considered the ninth planet of our Solar System. However in 2006, astronomers revised their definition of a planet and decided that Pluto is actually a dwarf planet, or minor planet. Many scientists now believe that Pluto is the largest dwarf planet in the Kuiper belt, a large group of bodies that orbit beyond Neptune. Pluto is markedly different from the major planets. It is significantly smaller and its unique orbit occasionally brings it closer to the Sun than to Neptune.

Encourage your children to explore beyond this movie and visit their local library or research on the Internet to learn more. NASA’s website contains a wealth of current, grade-appropriate information. A visit to a natural history museum or planetarium will help inspire children to learn more and explore the world beyond Earth.