Newly Pinpointed 'Venus Zone' Could Help Astronomers Hunt for Life on Exoplanets

Scientists have officially identified and characterized what they're now calling the "Venus Zone," the area around a star in which a planet is likely to have similar unlivable conditions that can be found on the planet Venus. This could allow astronomers to better understand which planets are likely to support life and which planets are too inhospitable.

"We believe the Earth and Venus had similar starts in terms of their atmospheric evolution," said Stephen Kane, one of the researchers, in a news release. "Something changed at one point, and the obvious difference between the two is proximity to the sun."

Currently, scientists are attempting to find exoplanets located within or near the habitable zone in which a planet can hold liquid water on its surface. Yet the main way this search is conducted is by looking for exoplanets that are roughly the same size as Earth. This, in particular, can pose a problem since while planets can be near Earth's size, like Venus, they may be completely inhospitable to life. That's why scientists decided to characterize this Venus Zone in order to streamline the search for planets.

In this case, the scientists used "solar flux," which is the amount of a star's energy that a planet receives, in order to define both the inner and outer edges of the Venus Zone. This allowed them to pinpoint at which point a planet's atmosphere would experience runaway greenhouse-gas effects like those seen on Venus. If astronomers discover a planet that's similar in size to Earth but located within the solar-flux range that makes up the Venus Zone, it can tell them that the planet may be more Venus-like than Earth-like.

"If we find all of these planets in the Venus Zone have a runaway greenhouse-gas effect, then we know that the distance a planet is from its star is a major determining factor," said Kane. "That's helpful to understanding the history between Venus and Earth."

Currently, scientists plan to look at whether the amount of carbon in a planet's atmosphere also impacts the Venus Zone. This could give astronomers a leg up in their hunt for life on other planets.

The findings are published in The Astrophysical Journal Letters.