TESS spots 27 possible new worlds by timing eclipses of binary stars

Astronomers using NASA's Transiting Exoplanet Survey Satellite (TESS) have identified 27 candidate planets orbiting pairs of stars, using a technique that watches for tiny shifts in when the stars eclipse one another. The approach can flag worlds that classical transit searches, which look for a single star dimming, often miss.

The work, led by doctoral candidate Margo Thornton at the University of New South Wales Sydney, examined 1,590 eclipsing binary systems that TESS had monitored for at least two years. When an unseen planet tugs on a binary, the timing of each eclipse drifts by seconds or minutes in a predictable pattern. Sifting through that signal in long, dense TESS light curves let the team flag candidates ranging from roughly 12 Earth masses up to about 10 Jupiter masses.

'The key to calculating all of these different influences is the long, rich set of observations available from TESS,' said co-author Benjamin Montet. The team published the results in Monthly Notices of the Royal Astronomical Society.

The candidates still need follow-up confirmation. Eclipse timing variations can also be caused by stellar activity, a third unseen star, or relativistic effects, so each system will require independent measurements before any object is officially counted as a planet. Even so, the technique broadens the kinds of worlds astronomers can hunt for, especially in tight binaries where planets may form on unusual orbits.

TESS, launched in 2018, has now confirmed 885 exoplanets and turned up more than 7,900 candidates. Studies like this one show that the mission's data still holds plenty of unmined signals years after the original observations were collected.