When Stars Shine Too Bright, Coronagraph "Sees" Past Glare

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Coronagraph on display in the Museum's Cullman Hall of the Universe, with a photo next to it of objects in space.

The coronagraph filters excess light from nearby stars, allowing scientists to better study objects that don’t shine as brightly in the night sky.

© AMNH/D. Finnin

Astronomers depend on interpreting the light from distant objects to study the universe. But sometimes, that same light can also get in the way, preventing scientists from seeing everything that’s out there.

Since 1995, Curator Rebecca Oppenheimer in the Department of Astrophysics has been working with colleagues on new astronomical instruments to develop an advanced tool that filters starlight from telescope images. By turning down the brightness of nearby stars, the technique, called a coronagraph, makes it possible for researchers to directly observe faint celestial objects orbiting nearby stars.

“In 1995, we used a primitive coronagraph, now exhibited in the Cullman Hall of the Universe, to discover and study the first brown dwarf, an object intermediate between planets and stars,” Oppenheimer says. “Since then we have built three new, far more advanced coronagraphs in the astrophysics lab here at the Museum and actually conducted some of the first reconnaissance of nearby solar systems quite different from our own.”

The early coronagraph on view at the Museum isn’t just an artifact of space exploration. It’s an early product of the research and development that took place only a few flights up from where it’s now exhibited. Much of the technology was produced by Oppenheimer and her team, then taken into the field for detailed studies of the atmospheres and orbits of alien solar systems—revealing parts of our universe previously hidden from us by the glare of other stars.


A version of this story originally appeared in the Fall 2017 issue of Rotunda, the Member magazine.