Part of Hall of the Universe.
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.
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.