In this artistic rendering, different kinds of suns are shown as they interact with various Earth-like surfaces in distant solar systems. The combinations create an array of climates. In the search for exoplanets, astronomers can be guided by color for possible habitable planets.
Credit: Jack Madden/Cornell

Large ground- and space-based telescopes will be able to observe Earth-like planets in the near future.

Cornell astronomers have developed an environmental color “decoder” – to tease out climate clues for potentially habitable exoplanets in galaxies far away.

The researchers see their work as helping to spot different planetary surfaces that are strongly influenced by climate, atmospheric composition, and remotely detectable spectra – a way to model potentially habitable rocky exoplanets.

Reflected light

“We looked at how different planetary surfaces in the habitable zones of distant solar systems could affect the climate on exoplanets,” said Jack Madden who works in the lab of Lisa Kaltenegger, associate professor of astronomy and director of Cornell’s Carl Sagan Institute.

“Reflected light on the surface of planets plays a significant role not only on the overall climate,” Madden said, “but also on the detectable spectra of Earth-like planets.”

Madden and Kaltenegger are co-authors of “How Surfaces Shape the Climate of Habitable Exoplanets,” released May 18 in the Monthly Notices of the Royal Astronomical Society.

This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere.
ESO/L. Calçada

Calculate a climate

In their research, they combine detail of a planet’s surface color and the light from its host star to calculate a climate. For instance, a rocky, black basalt planet absorbs light well and would be very hot, but add sand or clouds and the planet cools; and a planet with vegetation and circling a reddish K-star will likely have cool temperatures because of how those surfaces reflect their suns’ light.

Madden said forthcoming instruments like the Earth-based Extremely Large Telescope will allow scientists to gather data in order to test a catalog of climate predictions.

“There’s an important interaction between the color of a surface and the light hitting it,” Madden said. “The effects we found based on a planet’s surface properties can help in the search for life.”

The Brinson Foundation and the Carl Sagan Institute supported this research.

To read “How Surfaces Shape the Climate of Habitable Exoplanets,” released May 18 in the Monthly Notices of the Royal Astronomical Society, go to:

Note: Article based on Cornell Chronicle story by Blaine Friedlander

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