Dimming Starlight

  • Exhibition Text

    • Telescopes can easily zoom in on a star. But to see a dim object next to a star, such as a planet, astronomers need to block out the star’s light. A coronagraph attached to a telescope can eliminate nearly all the starlight, revealing dim objects nearby. With this coronagraph, researchers made the first discovery of a starlike object called a brown dwarf. Today coronagraphs are helping astronomers search for new planets.

      Hidden Planets

      If you looked at our Sun from a telescope 30 light years away, its light would be so bright it would obscure all the planets. Using a telescope with a coronagraph, Jupiter and Saturn would become visible.

      The coronagraph in this case was attached to the 60-inch (1.5 meter) wide telescope at the Palomar Observatory in southern California. With it, researchers made the first discovery of a brown dwarf as well as several "debris disks" where planets take shape.

      Show more
  • For Educators

    • Topic: Astronomy

      Subtopic: Stars

      Keywords: Coronagraphs, Light, Astronomy, Stars, Brown dwarf stars

      Audience: General

In This Section



Inside the coronograph, a series of mirrors and lenses position and focus the light. Carefully placed disks and rings block out 98.5% of the star's light, enabling astronomers to see dim objects near the star.