TOI-2535 b: the Jupiter-sized exoplanet that vanished from TESS

It did not stay normal. The transits, the dips in starlight when a planet passes in front of its star, became erratic. Sometimes the planet arrived up to six hours early, sometimes six hours late. More striking was the path itself, which crept toward the star's edge. Each crossing lasted less time and blocked less light, until between 2025 and March 2026 the transit vanished completely. From Earth, the planet no longer passes in front of its star.

According to the study, this is the first time astronomers have directly seen a confirmed planet around a single star stop transiting over such a short span. The distance between the star's centre and the planet's path changed by about 0.16 per year, the fastest rate ever measured in a system like this.

Why did TOI-2535 b stop transiting?

The team turned to NEID, a spectrograph on the WIYN telescope at Kitt Peak National Observatory in Arizona. The results point to a second planet with a mass at least similar to Saturn's. Its orbit is tilted by at least 5 degrees relative to TOI-2535 b, and because the two are so close, its gravity keeps pulling on the first planet. The orbit wobbles like a spinning top about to fall. The effect is called nodal precession.

Co-author Erik Petigura offers an analogy: if the Moon's orbit were perfectly aligned with Earth's, we would get a solar eclipse every month. Because it is tilted, eclipses are rare. At TOI-2535, the two planets keep changing that tilt over just a few decades.

Has this happened before?

Sort of. Kepler-413b stopped transiting for 800 days, but it orbits two stars, and their pull was the cause. TOI-1518b has a precessing orbit and may stop transiting in a few decades, but there the culprit is its own star's flattened shape. TOI-2535 stands out because another giant planet alone causes the change, in a system with two gas giants on very short orbits.