Scientists are hunting for planets that could support life –– specifically ones the same size as Earth.
But NASA has now realized hidden stars may have caused it to underestimate the size of some candidates it's already found.
When gauging a planet's dimensions, scientists are looking for light –– and then the lack of it.
They measure how bright a star is, and then how much light is blocked when a planet crosses our view of that star. The dimmer the readings get, the bigger the planet.
It's a pretty good system, except when scientists don't realize a planet is actually blocking our view of two stars.
If two stars are lined up back-to-back, but scientists don't know they're both there, they'll underestimate just how much light the planet is blocking — and thus, just how big the planet really is.
Luckily, it's not a problem for most planetary candidates. But getting close estimates for all planets is still really important.
Scientists have noted a planet twice the size of Earth or larger likely isn't habitable.