Download Solar System Study Guide 1

Solar System Study Guide 4
Facts:
 Even though you can’t feel it, Earth moves through space at nearly 30 kilometers
(about 19 miles) per second. At this speed our planet moves around the sun
almost 100 times as fast as most jet planes cruise.
 Our sun is a star, a burning sphere of gases. This enormous fiery ball is more
than 1 million kilometers (about 621,000 miles) in diameter. The sun is the
largest object in the solar system. It is larger than all the others put together.
 The sun puts out a lot of energy in all directions. It is the source of almost all the
energy in our solar system. Some of this energy reaches the Earth as light, and
some reaches it as heat.
 The dark areas of the sun are called sunspots. They are cooler than the rest of the
sun’s surface and don’t give off as much light.
 The red streams and loops of gases that shoot out from the sun are called
prominences. These hot fountains often begin near a sunspot. They can be
thousands of kilometers high and just as wide. Sunspots and prominences usually
last for only a few days. Some can last for a few months.
 The largest object in our solar system is the sun.
 The sun has 99.8 percent of the mass of our solar system.
 Each planet travels in its own orbit, a path around the sun.
 A planet, such as Earth, is a large object that moves around a star. Most planets
in our solar system also have at least one natural satellite, or moon. Earth has
only one moon.
 Asteroids and comets are other objects that move around the sun. Asteroids are
small and rocky. Most of them are scattered in a large area between the orbit
paths of Mars and Jupiter. Some scientist hypothesize that asteroids are pieces of
planets that never formed. All the asteroids put together would make an object
less than half the size of Earth’s moon.
 A comet is a small mass of dust and ice that orbits the sun in a long, oval shaped
path. When a comet’s orbit takes it close to the sun, some of the ice on the
comet’s surface changes to water vapor and streams out to form a long, glowing
tail.
 The time for one complete orbit by a planet around the sun is its year. Planets
with orbits closer to the sun move faster around the sun than those with orbits that
are farther away.
Harcourt Science D68-73