Planets Beyond Our Solar System

Look up at the night sky and imagine how many stars are out there. Thousands? Millions? Billions? In places far away from city lights, the night sky is much darker with many more stars visible to the human eye. One of the darkest night skies in the world can be found in a desert in northern Chile, at the Paranal Observatory. Scientists call it an “astronomer’s paradise.” Watch the video to see what the night sky looks like there.

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For thousands of years, people have looked up at the night sky and wondered if there could be life on other planets. Could there be a distant planet like Earth—one that is rocky, is just the right distance from its star so that it is not too hot or too cold, has liquid water, and has an atmosphere that might support life? In this activity, you will investigate how astronomers look for and locate exoplanets, planets that orbit stars other than Earth’s Sun. It might surprise you to know that the key to finding Earthlike exoplanets lies in studying stars.

Guess how many stars there are in the entire universe?

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No one knows for sure. Estimates range from 100 to 400 billion stars in the Milky Way galaxy alone and more than a trillion galaxies in the observable universe.

Scientists are searching for stars similar in size and temperature to our Sun. In 1995, the first exoplanet orbiting a Sun-like star was found in the Pegasus constellation, about 50 light-years away from Earth. Since that time, astronomers and amateurs have joined in an exciting hunt to discover more exoplanets. By 2020, more than 4,000 exoplanets had been confirmed.