Searching for the Invisible

by Diane K. Fisher

This giant dish antenna is about the size of a soccer field! It is part of NASA's Deep Space Network and is used to send and receive messages from its robotic space explorers.

Three blind flies land on an elephant. Each crawls over his part of the elephant and describes what he touches. The first one explores the trunk and says, "This creature is a wrinkled snake." The second one walks around on an ear and says, "This isn't a creature at all. It's a pancake." The third one hikes up and down the tail and says, "You are both crazy. This is nothing but a skinny rope hanging down from the sky."

If we are lucky enough to see the whole elephant at once, we understand how magnificent this animal really is.

So it is with astronomy. If we have only our poor eyes to look at the night, we see only a tiny part of the Universe. There is so much more to it than our eyes can see!

The light we see is but a tiny part of the light all around us. Therefore, humans have invented special telescopes that can see these different kinds of light. Using these new telescopes, both from the ground and from space, we have begun to see the entire elephant… er, Universe.

One kind of light we can't see is radio waves. We have learned to make our own radio waves for sending TV, radio, and cell phone signals through the air. Radio waves also come from stars (including our Sun), planets, clouds of gas in space, black holes, and other strange objects in space.

The telescopes that see radio waves don't look anything like the telescopes that see visible light. Radio telescopes are large dish-like antennas that can point to different parts of the sky. In addition to radio wave astronomy, NASA also uses this type of antennas—equipped with transmitters—to communicate with its unmanned spacecraft out there exploring the solar system.

Telescopes for seeing some kinds of light, such as x-rays and ultra-violet light, work best in space, because Earth's atmosphere blocks most of these kinds of light from reaching the surface. Several space telescopes now orbit Earth, each seeing a different kind of light.

Astronomers can now study images and data from all different types of telescopes just to understand one star or galaxy. They know that looking at the Universe in only one kind of light is like touching only the ear of the elephant.

Use the "Cosmic Colors" viewer at The Space Place, http://spaceplace.nasa.gov, to see places in the night sky through the eyes of many of these very special telescopes.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.