Almost all planets have been discovered by the 'transit' method, which is when a planet crosses in front of its star, creating a mini-eclipse.
This eclipse causes a dip in the starlight signal sent to Earth, suggesting there might be a planet orbiting there.
But the transit method restricts us to only discovering planets that cross between Earth and their star. If a planet orbits its star (or stars, in this instance) at an irregular orbit, or an orbit that isn't in our direct line of sight, it can slip under our radar.
"We're missing a huge part of the architecture for these systems," says A/Prof. Montet.
The new method helps astronomers detect planets like these that we might have otherwise missed – helping to build our knowledge of what type of environments can support planet development.
"With this method so far, we have 27 strong planet candidates in environments completely unlike our own solar system," says Ms Thornton, who made these findings just one year into her PhD.
"By learning more about different types of planets, we can better understand how planets form and evolve, especially in these complex environments with two stars."
The planets are called 'candidates' for now as the team need to confirm, or deny, their planet status using an additional observation method.
Ms Thornton has started work on this process and hopes to have a follow-up paper ready within the next year.
Our circumbinary neighbours
The planet candidates range from objects that could be as small as the mass of Neptune to 10x as large as the mass of Jupiter.
The closest is about 650 light years away from Earth, and the furthest about 18,000 away. To put this in perspective, one light year is 9.4 trillion kilometres.
"The candidates are scattered across both our southern and northern skies," says A/Prof. Montet.
"This means that any time of the year, no matter when you're looking, at least one of these star systems is out there visible for you to look towards – as long as you have a telescope."
Even though the candidates stretch across immense distances, they're still relatively close to our 'neighbourhood' in the Milky Way – although our list of circumbinary planet neighbours may soon be growing.
"We found 27 planet candidates out of 1590 binary star systems, which is an almost 2% rate of binary systems that could potentially host planets," says A/Prof. Montet.
"That implies there could potentially be thousands, or tens of thousands, of possible planets to be found with data from the Vera C. Rubin Observatory's new 10-year sky survey, the Legacy Survey of Space and Time.
"So it's a really exciting first step – and it also shows that there's going to be a lot of work to do over the next few years."
Learning about other worlds
Most of the planets we know about in the universe are in single star systems, like our solar system.
But cosmically speaking, systems like ours are in the minority: more than half of the stars in the universe are in binary or multiple star systems.
"We've painted half a picture, and the other half of the canvas is completely blank," says A/Prof. Montet.
Astronomers still have a lot of questions about planet formation in these systems – and this new planet-hunting method could help fill some of those knowledge gaps.
"We can start asking questions like how common these planets are overall and if they could be habitable," says A/Prof. Montet.
"If circumbinary planets do turn out to be habitable, that means life could be anywhere. Life could be everywhere. The sheer numbers are really exciting."
