Study: TESS Saw Transits of Exoplanet TOI-2535 b Fade and Disappear

Astronomers say they have documented the first confirmed case of a planet around a single star whose transits were directly seen to disappear. In the newly published study, researchers report that the giant exoplanet TOI-2535 b stopped crossing the face of its star from Earth’s point of view while NASA’s TESS space telescope was still watching, not because the planet vanished, but because another planet appears to have tilted its orbit out of view.

The study, “A TESS Disappearing Act: The Vanishing Transits of TOI-2535 b,” by Samuel W. Yee and co-authors, was published in The Astrophysical Journal Letters in 2026 and posted to arXiv on Nov. 9, 2026. The authors describe TOI-2535 b as a hot Jupiter, a gas giant orbiting very close to its star, completing one trip every roughly 8.2358 days.

Their case rests on seven years of photometry from TESS, spanning April 2019 to March 2026. Over that period, the planet’s transit changed from a more central crossing of the star to a grazing transit, where the planet clipped only the edge of the stellar disk, and then to no detectable transit at all. The key non-detection came in TESS Sector 101 in March 2026, when the authors say injection-recovery tests ruled out a significant transit at the predicted times.

The paper lays out several signs that the system’s geometry was changing in real time. The apparent path of the planet across the star, measured by a quantity called the impact parameter, shifted at a rate of 0.16 per year. At the same time, the transit mid-times drifted by as much as plus or minus 6 hours from a simple linear schedule. Together, those changes point to more than routine measurement scatter: They suggest that TOI-2535 b’s orbit was being perturbed as TESS observed it.

To investigate what was driving that behavior, the team combined the TESS timing and duration data with radial-velocity measurements from NEID, a spectrograph on the WIYN 3.5-meter telescope at Kitt Peak that detects the back-and-forth motion of a star under the pull of orbiting planets. Their modeling points to an additional nearby planet, likely Saturn-mass or larger, moving on an orbit tilted by at least about 5 degrees relative to TOI-2535 b. The authors say the unseen companion is probably in or near a mean-motion resonance with the hot Jupiter, meaning their orbital periods are linked in a repeating gravitational pattern, but they also stress that multiple dynamical solutions fit the data, including 2:1 and 3:2 resonance families.

In the researchers’ interpretation, the main cause of the disappearing transit is precession of the orbital planes — a slow change in orientation caused here by planet-planet interactions. That matters because a transit can be seen only when a planet’s orbit is lined up just right with Earth. If that alignment shifts, a planet can stop transiting even though it remains in the system.

The host star is somewhat smaller and cooler than the sun, with about 0.864 times the sun’s mass, 0.877 times its radius and a temperature of 5,256 kelvins. The system also appears unusual because it may contain two short-period giant planets.

The result offers a direct example of orbital evolution unfolding on human timescales. It also underscores a limitation of transit surveys, which find planets by watching for periodic dips in starlight: Some planets may be there but temporarily nontransiting when telescopes happen to look. The authors say earlier cases have been suggested, but they distinguish TOI-2535 b as the first confirmed single-star system where the transits were directly observed to disappear. In representative models, the precession cycle lasts decades, and TOI-2535 b could return to a transiting alignment in roughly 30 to 50 years.