Our experts answer your questions

Dr Jack Madden is an astrophysicist at Cornell University, New York

EXOPLANETS

How does a planet’s colour influence its habitability?

Much like a white shirt keeping you cool on a bright summer day, a planet’s colour plays an important role in keeping a planet’s temperature just right for life. Our search for life is currently focused on finding exoplanets with temperatures in a range that allow for liquid surface water. An exoplanet with a dark surface like ocean or basalt will absorb a lot of the incoming stellar energy and heat up. A brighter surface like snow or sand will reflect stellar energy and prevent the temperature from rising.

Darker exoplanets typically absorb more heat than lighter reflective ones

© NASA/JPL-Caltech

Because colour plays such an important role in temperature, there are sweet spots in the interaction between type of starlight, exoplanet colour and exoplanet-star distance that allow for liquid water to exist. Having a better understanding of this complex system of interactions will help us find a habitable planet.

In the coming decade we will be able to assess the habitability of exoplanets with direct measurements. Until then we need to model many different scenarios so we are prepared for a wide range of possible environments. By modelling the way exoplanet colour influences habitability, we can focus our search on the exoplanets that show the most promise for life. This gives us a way to compare real observations with the physics we expect.

SOLAR SYSTEM

Could asteroids still be forming in the Solar System?