One way astronomers look for extrasolar planets is with radio telescopes. Detecting and measuring changes in the amount of light a star gives off helps these scientists estimate the mass of an object that is orbiting the star. To learn more about extrasolar planets:

1. Go to the Discovering New Worlds WWW Sheet and print it.

2. Visit this Web site. Read "If we can't see them, how can we find if there are planets around other stars?" Then complete the WWW Sheet.
    The Search for Planets

3. For more information, visit this Web site. Read "The Methods: Planets' Effects Give Them Away" on page 4.
     Scientists Step Up Search