Systems with two stars could be hiding Earth-sized planets in plain sight

Beyond the solar system, there could be many more Earth-sized planets that are part of two star systems, according to a new study.

The research, set to be published in Astronomical Journal, notes that Earth-sized worlds could be a part of binary star systems, hidden by the glare of the stars they orbit.

Experts from NASA’s Ames Research Center looked at NASA’s Transiting Exoplanet Survey Satellite (TESS) and found that 73 of the hundreds of nearby stars that TESS identified as potential exoplanet hosts appeared as just a single point of light until they were examined closer by the telescopes of the Gemini Observatory in Hawaii and Chile.

‘After identifying the binary stars, the team compared the sizes of the detected planets in the binary star systems to those in single-star systems,’ according to a statement from NOIRLab. 

‘They realized that the TESS spacecraft found both large and small exoplanets orbiting single stars, but only large planets in binary systems.’

Seventy-three of the hundreds of nearby stars that NASA’s Transiting Exoplanet Survey Satellite (TESS) identified as potential exoplanet hosts appeared as a single point of light until examined closer

The researchers also looked at how far apart the stars are in the binary systems and noted that stars with planets were ‘typically farther apart’ than those systems that don’t have a planet

The researchers also looked at how far apart the stars are in the binary systems and noted that stars with planets were ‘typically farther apart’ than those systems that don’t have a planet.

‘This could suggest that planets do not form around stars that have close stellar companions,’ the statement added.    

It’s the light from the second star that makes it more difficult to detect changes in the host’s star light when the planet crosses in front of it, which is currently the best method for finding planets outside the solar system.

‘We have shown that it is more difficult to find Earth-sized planets in binary systems because small planets get lost in the glare of their two parent stars,’ the study’s lead author and NASA Ames researcher Katie Lester said in the statement. 

Luke Skywalker’s view of two suns from his aunt and uncle’s moisture farm in the first-released Star Wars film is fictional, but this research suggests Earth-like planets could be part of double-star systems, similar to Tatooine (pictured)

Perhaps the most famous planet with a binary star system is the fictional Tatooine, Luke Skywalker’s home planet in the ‘Star Wars’ films. 

So far, TESS has confirmed the existence of 131 exoplanets and identified 4,190 candidates during its more than three-year long mission, which is currently ongoing.  

TESS was successfully launched in April 2018 as the successor to the Kepler Space Telescope.

‘Since roughly 50% of stars are in binary systems, we could be missing the discovery of — and the chance to study — a lot of Earth-like planets,’ Lester concluded.  

The new findings come just days after a separate group of researchers suggested that Earth-like conditions  could be far fewer than previously imagined.

That study found there is just one other planet in the galaxy – Kepler-442b – that receives enough sunshine from its star to form a biosphere with ‘oxygenic’ photosynthesis, which the authors note is a crucial part of complex life. 

Several other binary star systems with exoplanets have been found in recent years, including Kepler-1647 b, in June 2016, which is 3,700 light-years from Earth.

In December 2020, a Jupiter-like planet called HD106906b was found to orbit two stars 336 light-years away.

In May, five double-star systems, each with a planet capable of supporting life, were discovered thanks to NASA’s Kepler space telescope.