New ‘climate decoder’ to study potentially habitable exoplanets
Over 4,000 exoplanets – worlds orbiting other stars – have been confirmed so far. But these planets are very far away, and we still don’t know much about them. To find out more, newer technology and observations are needed. To that end, scientists at Cornell University have developed a new tool – an environmental color “climate decoder” – that they hope will help astronomers learn more about the climates on some of these distant worlds, particularly potentially habitable Earth-sized planets.
We looked at how different planetary surfaces in the habitable zones of distant solar systems could affect the climate on exoplanets. Reflected light on the surface of planets plays a significant role not only on the overall climate, but also on the detectable spectra of Earth-like planets.
The research is in anticipation that new telescopes, such as the upcoming Extremely Large Telescope (ELT) in Chile, will soon be able to study potentially habitable planets more closely than ever before. As stated in the paper:
Large ground- and space-based telescopes will be able to observe Earth-like planets in the near future. We explore how different planetary surfaces can strongly influence the climate, atmospheric composition, and remotely detectable spectra of terrestrial rocky exoplanets in the habitable zone depending on the host star’s incident irradiation spectrum for a range of sun-like host stars from F0V to K7V. We update a well-tested 1D climate-photochemistry model to explore the changes of a planetary environment for different surfaces for different host stars. Our results show that using a wavelength-dependent surface albedo is critical for modelling potentially habitable rocky exoplanets.
The researchers looked at two basic aspects of such exoplanets – the surface color and the light coming from the host star – in order to calculate what the climate might be like on a given planet. There can be a lot of variables to consider; if a planet was covered in dark basalt, that could cause the planet to be very hot, just like hot pavement in summertime. But if there was also a lot of clouds or sand, or even oceans, then the planet might be cooler. If there were a planet orbiting a red dwarf star that happened to have vegetation, then it might also have cooler temperatures. Madden said:
Think about wearing a dark shirt on a hot summer day. You’re going to heat up more, because the dark shirt is not reflecting light. It has a low albedo (it absorbs light) and it retains heat. If you wear a light color, such as white, its high albedo reflects the light, and your shirt keeps you cool.
Madden’s colleague, and the other coauthor of the study, Lisa Kaltenegger, added:
Depending on the kind of star and the exoplanet’s primary color – or the reflecting albedo – the planet’s color can mitigate some of the energy given off by the star. What makes up the surface of an exoplanet, how many clouds surround the planet, and the color of the sun can change an exoplanet’s climate significantly.
There’s an important interaction between the color of a surface and the light hitting it. The effects we found based on a planet’s surface properties can help in the search for life.
Being able to determine what the climate is like on some exoplanets, at least to some degree, will of course help scientists determine which ones could be the most habitable. New upcoming telescopes, like the ELT, will be essential in that endeavour.
A growing number of Earth-sized and super-Earth worlds – larger and more massive than Earth but smaller than Neptune – are being discovered, including in the habitable zones of their stars, the region where temperatures could allow liquid water to exist.
This is encouraging in the search for life elsewhere.
But various factors can affect habitability, such as the composition of the atmosphere and planet itself, abundance or lack of water, the amount of radiation coming from the planet’s star and the actual temperatures. There’s no guarantee that any of these planets could host life, so techniques like the new climate decoder will help scientists determine which ones are the most favorable, at least by earthly standards.
With over 4,000 confirmed exoplanets found already, and thousands more expected in the near future, techniques like the climate decoder will be essential for learning not only what conditions are like on some of these distant worlds, but also whether some of them could be home to the holy grail of exoplanet research … life itself.
Bottom line: Scientists have developed a new technique to figure out what the climate is like on potentially habitable exoplanets.