What Is a Lagrange Point?

NASA’s James Webb Space Telescope will travel to a special spot where the gravity from Earth and the sun is balanced

Telescope trajectory.

Matthew Twombly


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The most ambitious space telescope built to date is about to start peering at the universe through infrared eyes. The $10-billion James Webb Space Telescope (JWST) is designed to see farther back in space and time than ever before, where light has been stretched by the expansion of space into much longer wavelengths. To see this faint light, the telescope must observe far from Earth and its contaminating light and heat. After launch, JWST will travel 1.5 million kilometers to Earth's second “Lagrange point” (L2), a spot in space where the gravitational forces of our planet and the sun are roughly equal, creating a stable orbital location. This vantage point will allow JWST to orbit with its giant sunshield positioned between the telescope and the sun, Earth and moon, shielding the telescope and keeping it at a frigid –370 degrees Fahrenheit.

Credit: Matthew Twombly (graphic); Heidi B. Hammel/Shari Lifson/Association of Universities for Research in Astronomy (content consultants)

Clara Moskowitz is a senior editor at Scientific American, where she covers astronomy, space, physics and mathematics. She has been at Scientific American for a decade; previously she worked at Space.com. Moskowitz has reported live from rocket launches, space shuttle liftoffs and landings, suborbital spaceflight training, mountaintop observatories, and more. She has a bachelor's degree in astronomy and physics from Wesleyan University and a graduate degree in science communication from the University of California, Santa Cruz.

More by Clara Moskowitz

Matthew Twombly is a freelance illustrator and infographic designer. His work can be viewed at www.matthewtwombly.com

More by Matthew Twombly
Scientific American Magazine Vol 326 Issue 1This article was originally published with the title “A Telescope's Long Journey” in Scientific American Magazine Vol. 326 No. 1 (), p. 80
doi:10.1038/scientificamerican0122-80