Zero Genie

Astronomers at Cornell University have built spectral templates of Earth’s environment representing five key eras in the planet’s evolution to help in the search for Earth-like exoplanets using next-generation telescopes.

The research, carried out by Lisa Kaltenegger, associate professor of astronomy at Cornell and director of the Carl Sagan Institute, and doctoral students Jack Madden and Zifan Lin ’20, was published in Astrophysical Letters.

“These new generation of space- and ground-based telescopes coupled with our models will allow us to identify planets like our Earth out to about 50 to 100 light-years away,” said Kaltenegger.

“Using our own Earth as the key, we modelled five distinct Earth epochs to provide a template for how we can characterise a potential exo-Earth, from a young, prebiotic Earth to our modern world. The models also allow us to explore at what point in Earth’s evolution a distant observer could identify life on the universe’s ‘pale blue dots’ and other worlds like them.”

The atmospheric models mirror Earth’s pre-biotic environment 3.9 billion years ago, an oxygen-free planet 3.5 billion years ago and three other models showing the rise of oxygen in the atmosphere from 0.2 percent to modern-day levels of 21 percent.

“Our Earth and the air we breathe have changed drastically since Earth formed 4.5 billions years ago,” Kaltenegger said, “and for the first time, this paper addresses how astronomers trying to find worlds like ours, could spot young to modern Earth-like planets in transit, using our own Earth’s history as a template.”

She said upcoming telescopes like the European Southern Observatory’s Extremely Large Telescope in Chile and NASA’s James Webb Space Telescope should be able to spectroscopically dissect the atmospheres of transiting exoplanets and, using the Earth templates, possibly discern the tell-tale signs of environments where life might be possible.