Dr. Craig Walton: “This makes searching for life on other planets a lot more specific. We should look for solar systems with stars that resemble our own Sun.”

How common are Earth-like worlds beyond our solar system? This is what a recent study published in Nature Astronomy hopes to address as an international team of scientists unveiled new evidence that Earth-like worlds might be rarer than previously thought. This study has the potential to help scientists better understand the formation and evolution of Earth-like worlds and what this could mean for finding life beyond Earth.

For the study, the researchers used a series of computer models to simulate the formation of the interiors of potential Earth-like worlds, specifically focusing on planetary interior formation. This is because the researchers note how nitrogen and phosphorus are essential for the formation of habitable worlds, and the planetary mantle, the layer just beneath the planetary crust, is where they are formed and exist.

In the end, the researchers found that the right amount of oxygen needs to be present within the mantle for nitrogen and phosphorus to form. They note while Earth has these conditions, worlds with less oxygen in their mantle could limit the ability of nitrogen and phosphorus to form, resulting in non-habitable worlds.

“Two things can happen: Either the planet gets very, very close to the binary, suffering tidal disruption or being engulfed by one of the stars, or its orbit gets significantly perturbed by the binary to be eventually ejected from the system,” said Dr. Mohammad Farhat.

Why is it so rare to find exoplanets orbiting two stars, also called circumbinary planets (CBPs)? This is what a recent study published in The Astrophysical Journal Letters hopes to address as a team of researchers investigated the celestial processes responsible for the formation and evolution of CBPs. This study has the potential to help scientists better understand solar system and planetary formation and evolution, which could narrow the search for life beyond Earth.

For the study, the researchers used a combination of computer models and Einstein’s theory of relativity to simulate the formation and evolution of CBPs. For example, the researchers explored the interaction between the CBP and its binary star, resulting in one of three outcomes: stable orbit, ejection, or consumption by the binary star. The reason Einstein’s theory of relativity was used as part of the study was because it calls for objects to have their orbit perturbed the closer they orbit to a larger object, like a star.

A common example that’s used for the theory is of a trampoline with objects falling inward when a large body is in the middle of it. Essentially, stars have “instability zones” where planets get consumed if they orbit too close. In the case of CBPs, the astronomers found that of the 14 known CBPs out of more than 6,000 confirmed exoplanets, 12 orbit just beyond the instability zone and none of the 14 have orbits less than seven days. The researchers concluded that a common phenomenon in astronomy called the three-body problem is responsible for the lack of CBPs.