A hot Jupiter called TOI-2535 b, orbiting a star roughly 1,000 light-years away, has effectively disappeared from transit observations. The planet remains in orbit; it has simply stopped crossing the visible disk of its star from our line of sight.
How Astronomers Spot Planets in the First Place
The transit method works only when a planet, its star, and Earth align closely enough to catch the brief dip in starlight.
When a planet passes across the face of its star, it blocks a small fraction of the star’s light. Telescopes detect that brief dimming as a transit. That is how NASA’s Transiting Exoplanet Survey Satellite, known as TESS, first identified TOI-2535 b in 2019.
The planet completes one orbit every 8.25 days, so transits were frequent and, for a while, reliable.
The Warning Signs Were There
Six hours of timing drift and shrinking transit signals pointed to something pulling the planet’s orbit out of alignment.
Researchers monitored the system for more than seven years, drawing on TESS data and ground-based radial-velocity measurements from the NEID spectrograph. What they found was strange.
Transit arrival times shifted by as much as six hours ahead of or behind schedule, while the transits generally became shorter and shallower over time. By 2026, the starlight dips stopped appearing entirely, according to findings published in The Astrophysical Journal Letters.
A Spinning Top Losing Its Angle
A related geometric effect can be illustrated by Earth’s eclipse seasons: orbital alignment is temporary, not permanent.
The mechanism behind the disappearance is called nodal precession, the slow wobble of an orbital plane over time, similar to the wobble of a spinning top as it shifts its angle. As TOI-2535 b’s orbit tilted, its path across the star crept toward the stellar edge and eventually moved entirely off the visible disk.
Earth’s own eclipses follow the same logic. The Moon’s orbit is slightly inclined relative to Earth’s path around the Sun, which is why a solar eclipse does not happen every month.
An Unseen Planet Did the Nudging
Gravitational fingerprints in the timing and velocity data point to a Saturn-sized companion that has never been seen in transit.
The wobble was not spontaneous. Researchers’ modeling points to a neighboring planet, likely at least Saturn-sized, whose gravity is tilting TOI-2535 b’s orbital plane away from our line of sight.
The two may be locked in a mean-motion resonance. That is a gravitational relationship in which orbital periods form a simple ratio, amplifying their mutual pull. This companion has never been observed crossing its star; it is currently inferred from gravitational fingerprints in the system’s timing and radial-velocity data.
Thirty to Fifty Years Until the Next Look
TOI-2535 b could become visible again within a human lifetime, and the unseen companion might cross the star even sooner.
Current models suggest TOI-2535 b may transit again in approximately 30 to 50 years, once its orbital plane wobbles back into alignment with Earth’s line of sight. The unseen companion could cross its star sooner, potentially becoming the system’s next detectable transit signal.
The broader implication is straightforward: transit surveys can miss planets that are physically present but geometrically out of position. Long-term monitoring, combined with radial-velocity observations and dynamical modeling, is what separates a lost civilization from a tilted one.
