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Exoplanet Diversity: Atmosphere

Starlight filtered through distant atmospheres Full Story Below

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An Earth-sized planet like TRAPPIST-1e could have an atmosphere similar to Earth’s.

Some warm Neptune-sized planets like GJ 436b are thought to be rich in methane.

Water can even exist on hot gas giants like WASP-62b, which are inhospitable to life as we know it.

Thicker and denser atmospheres block more light.

Warm Neptune-Sized
Hot jupiter-Sized

Exoplanet Diversity: Atmosphere

Every planet has a unique atmosphere.

Researchers have detected thousands of planets orbiting stars other than the Sun. The data show that these planets are even more varied than the planets and moons in our solar system. They range from small rocky planets a fraction of the size of Earth to large gas giants several times the size of Jupiter. Some orbit cool dwarf stars while others circle stars much hotter and more massive than the Sun. And like the objects in our solar system, they have a wide variety of compositions and structures.

Although no exoplanet is close enough to visit with a space probe, we can—under the right conditions—study an exoplanet’s atmosphere. When a planet passes in front of its star, some of the starlight is filtered through the planet’s atmosphere. We can analyze the pattern of the filtered light (a transmission spectrum) to figure out what the atmosphere is made of.

The transmission spectra shown here are models based on assumptions about the composition, temperature, and structure of the exoplanet’s atmosphere. In the future, scientists will compare actual data from observatories like the James Webb Space Telescope to the models to figure out which assumptions are correct and which are not.

Quick Facts: Atmosphere

Temperate Earth-sized exoplanet: TRAPPIST-1 e

Location: TRAPPIST-1 system, 40 light-years from Earth (inside the Milky Way)

Diameter: 0.9 times the size of Earth's diameter

Star: TRAPPIST-1, a very cool red dwarf

Warm Neptune-sized exoplanet: GJ 436 b

Location: Gliese 436 system, 30 light-years from Earth (inside the Milky Way)

Diameter: 4 times the size of Earth's diameter

Star: Gliese 436, a cool red dwarf

Hot Jupiter exoplanet: WASP-62 b

Location: WASP-62 system, 520 light-years away (inside the Milky Way)

Diameter: 15 times the size of Earth's diameter

Star: WASP-62, a hot blue-white star

Explore More About Exoplanet Diversity

Find out more with these additional resources from NASA’s Universe of Learning

Eyes on Exoplanets
Explore thousands of planetary systems orbiting distant stars
Exoplanet Watch
Do citizen science by observing exoplanets
Universe Unplugged
The Habitable Zone: Space explorers search for a new world
Illustrations of Exoplanets and Graphs of Exoplanet Data

Credits: Atmosphere

Illustration of exoplanet Trappist-1e: NASA/JPL-Caltech

Illustration of exoplanet GJ 436b: NASA, ESA, A. Feild, G. Bacon (STScI)

Illustration of exoplanet WASP-62b: Kyoto University

Model transmission spectra of Hot Jupiter and Warm Neptune exoplanet from ExoCTK and the generic grid based on the ATMO grid published in Goyal, J., et al., 2018b, MNRAS

Model transmission spectrum of Temperate Earth-sized exoplanet: Tyler Robinson

Content development by Margaret W. Carruthers, Timothy Rhue II, Dr. Christopher Britt, Dr. Brandon Lawton

Design by Elizabeth Wheatley, John Godfrey

Web development by Philippe Batigne

Subject-matter expertise provided by Dr. Hannah Wakeford, Dr. Kevin Stevenson