Surprising number of exoplanets could harbor life

Land. A new study shows that other stars could have up to seven Earth-like planets in the absence of a gas giant like Jupiter.

This is the conclusion of a study led by UC Riverside astrobiologist Stephen Kane published this week in the Astronomical magazine.

The search for life in outer space generally focuses on what scientists call the “habitable zone,” which is the area around a star in which an orbiting planet could have oceans of liquid water, a condition for life. as we know it.

Kane had been studying a nearby solar system called Trappist-1, which has three Earth-like planets in its habitable zone.

“This made me wonder about the maximum number of habitable planets a star can have and why our star only has one,” Kane said. “It didn’t seem fair!”

His team created a model system in which they simulated planets of various sizes orbiting their stars. An algorithm took gravitational forces into account and helped test how planets interacted with each other over millions of years.

They discovered that it is possible for some stars to support up to seven, and that a star like our sun could support six planets with liquid water.

“More than seven, and the planets get too close and destabilize each other’s orbits,” Kane said.

Why then does our solar system only have one habitable planet if it is capable of supporting six? It helps if the movement of the planets is circular rather than oval or irregular, minimizing any close contact and maintaining stable orbits.

Kane also suspects that Jupiter, which has a mass two and a half times that of all the other planets in the solar system combined, limited the habitability of our system.

“It has a great effect on the habitability of our solar system because it is massive and disrupts other orbits,” said Kane.

Only a handful of stars are known to have multiple planets in their habitable zones. In the future, Kane plans to search for additional stars surrounded by smaller planets. These stars will be prime targets for direct imaging with NASA telescopes like the Jet Propulsion Laboratory’s Habitable Exoplanet Observatory.

Kane’s study identified one of those stars, Beta CVn, which is relatively close to 27 light-years away. Because it does not have a Jupiter-like planet, it will be included as one of the stars controlled by planets of multiple habitable zones.

Future studies will also include the creation of new models to examine the atmospheric chemistry of habitable zone planets in other star systems.

Projects like these offer more than new avenues in the search for life in outer space. They also offer scientists information about the forces that could change life on our own planet someday.

“Although we know that Earth has been habitable for most of its history, many questions remain about how these favorable conditions evolved over time and the specific drivers behind those changes,” Kane said. “By measuring the properties of exoplanets whose evolutionary pathways may be similar to ours, we get a preview of the past and future of this planet, and what we must do to maintain its habitability.”