33 Outside the Solar System-Low

Outside the Solar System Written by Patricia Walsh and Ron Fridell

Introducing Deep Space Look up on a dark, clear night away from city lights. Do you see the points of light overhead? Most of the points of light are stars. Some points of light are huge groups of stars called galaxies. You are looking into deep space. Deep space is everything outside our Solar System. It is the space beyond our star—the Sun—and the planets that orbit the Sun. You're about to journey among the stars.

Exploring Space Telescopes give us a closer look at the objects in the night sky. Huge telescopes sit on top of mountains. Space telescopes orbit Earth. Radio telescopes gather radio waves from deep space. They let us see things we can't see with visible light. Word Wise The word telescope comes from the Greek word teleskopos. The word part tele- means "far" and -skopos means "seeing" Our modern-day telescopes let us see far into space.

People have gone into space. We have landed on the Moon. But no one from Earth has ever left our Solar System. No human being has gone into deep space. Pack your imagination. Get ready to take off. You will get a close-up look at the billions of stars, planets, and galaxies in our universe.

Out of This World You already know your own space neighbors. They are the Moon, the other planets, and our Sun. These are in our Solar System. But it is only a tiny part of the universe. Outside the Solar System is a huge amount of space. The universe has billions and billions of other objects in it. It's time to leave Earth, and head toward deep space. You're leaving our Solar System. Did you feel a bump? The bump is caused by solar wind. It reaches to where the Solar System ends and deep space begins. The bump should not have surprised you. An unmanned spacecraft named Voyager 2 traveled this far. It let scientists know about the bumpy solar winds. You're traveling faster than Voyager 2. Wave to it as you cross into deep space.

Among the Stars You've traveled a very long distance now. You have come 4.2 light-years from Earth. You're arriving at Earth's nearest star neighbor. It is Proxima Centauri, a dim, cool star. Do you see Proxima Centauri's partner, Alpha Centauri? Up close, you can see that Alpha Centauri has two stars that are just like our Sun. On Earth, you saw constellations. There were a lion, a swan, and a centaur. But now you're traveling among the stars. You'll see that these constellations aren't dots on a flat surface. They're stars that are very far from one another. Math Moment The distance between stars is huge. Scientists use a measurement called a light-year to measure it. A light-year is the distance light travels in one year. One light-year is about 9.5 trillion kilometers (5.9 trillion mi.) About how many kilometers (or mi.) from Earth is our closest star neighbor?