MISSION EXPLORING SPACE Have you ever wondered what's in space Maybe you'd like to become an astronomer You can get started in your own backyard Track the path of the sun across the sky Notice how the moon changes from one night to the next Looking Near For centuries we have studied space from the ground In 1609 Galileo Galilei used a handheld telescope Today astronomers use huge mountaintop telescopes Looking Far We can also explore space directly The National Aeronautics and Space Administration NASA first landed humans on the moon during the Apollo missions Today astronauts study on the International Space Station ISS
On a clear night with little light pollution you can see about 2 000 stars With a telescope you can spot even more Reaching for the Stars Astronomers collect data from the farthest stretches of the universe They can't observe everything directly But they can use math and physics to make guesses These guesses can teach us about our universe's past and future
CHAPTER 1 WAVES AND LENSES There are many types of telescopes Some work from Earth Others function in space Different telescopes see different light waves of the electromagnetic spectrum The electromagnetic spectrum contains every type of light wave This includes radio microwave infrared and other invisible light waves Special telescopes reveal these waves They allow researchers to see more of the universe Telescopes on the ground must fight against Earth's atmosphere Air turbulence warps the incoming data Because of this observatories are often located at high altitudes The air at these heights contains fewer molecules Fewer molecules means less turbulence Moisture also affects telescopes Damp air can warp lenses This is why many telescopes are in the desert Desert air contains fewer water molecules
THE ELECTROMAGNETIC SPECTRUM Radio Waves Microwaves Infrared Light Visible Light Ultraviolet Light X Rays Gamma Rays Low Frequency Long Wavelength High Frequency Short Wavelength Low frequency waves like radio waves have longer wavelengths High frequency waves like gamma rays have shorter wavelengths Instruments exist to detect every type of wave Space telescopes orbit Earth and the sun There they are beyond most atmospheric interference They can detect fainter wavelengths Astronomers combine images from multiple light waves This gives them a more complete picture of what they observe
