TOI-2535 b has not vanished. Seven years of TESS observations show its transits shrinking and disappearing, with researchers pointing to the gravitational influence of an unseen neighbouring planet.
Key facts at a glance
A planet that disappeared from the data, not from space
Astronomers studying the star system TOI-2535 have reported an unusual change: the hot Jupiter TOI-2535 b stopped passing in front of its star from Earth’s point of view. The planet has not been destroyed or ejected. Instead, its orbit appears to have tilted until the planet no longer crossed the visible face of the star along our line of sight. The finding was reported by a UCLA-led team and published in The Astrophysical Journal Letters in November 2026.
The discovery is based on seven years of observations from NASA’s Transiting Exoplanet Survey Satellite, or TESS, together with ground-based measurements. The transits became shorter and shallower over time, while their timing drifted by as much as six hours from a regular schedule. Researchers say the most plausible explanation is the gravitational influence of another planet on a mutually inclined orbit. That companion has not been directly detected; its presence is inferred from the way TOI-2535 b’s orbit has changed.
What a transit tells astronomers
A transit occurs when a planet passes between its star and the observer, blocking a small fraction of the star’s light. A telescope does not need to photograph the planet directly. It measures a tiny dip in brightness, and repeated dips can reveal the planet’s orbital period, size relative to the star and the geometry of its path. The method has been one of the most productive ways to discover exoplanets because it can be applied to thousands of stars at once.
The geometry is unforgiving. A planet can orbit its star regularly and still never produce a transit if its orbital plane is tilted too far from the line of sight. The same principle explains why solar and lunar eclipses do not occur every month on Earth. The Moon’s orbit is tilted relative to Earth’s orbit around the Sun, so the three bodies line up only at certain times. In the TOI-2535 system, astronomers have watched that alignment change on a human timescale.
A hot Jupiter on an eight-day orbit
TOI-2535 b is classified as a hot Jupiter, a gas giant that orbits much closer to its star than Jupiter does to the Sun. The planet completes one orbit in about 8.25 days. By comparison, Mercury takes 88 days to circle the Sun. UCLA reported that the system lies roughly 1,000 light-years from Earth, far beyond the reach of direct spacecraft exploration but accessible to precision photometry and spectroscopy.
The planet’s short orbital period means that it passes its star frequently, giving TESS and ground-based observatories repeated opportunities to measure the signal. The repeated transits made it possible to detect changes in duration and timing rather than relying on a single observation. A hot Jupiter’s close orbit also makes it sensitive to gravitational interactions with nearby massive companions. The planet’s rapid motion is not the cause of its disappearance; the key is the changing orientation of the orbital plane.
Seven years of TESS observations revealed a gradual shift
TESS observed the TOI-2535 system between April 2019 and March 2026. Over that period, the planet’s path across the stellar disk moved from a transit closer to the centre towards a grazing path near the edge. The dips in brightness became shorter and shallower. By the later observations, the planet no longer crossed the visible stellar disk in the way required to produce a transit signal.
The research team measured the change in the transit geometry and found an impact-parameter drift of about 0.16 per year. The impact parameter describes how far the planet’s projected path passes from the centre of the star. A value near zero corresponds to a central transit; a value closer to the stellar radius corresponds to a grazing event. The rapid change gave the team a way to track the orbital plane moving relative to the observer rather than simply noting that the transit signal had disappeared.
The timing variations offered a second clue
The duration of a transit reveals the path a planet takes across the star, but the time at which the transit occurs can also reveal gravitational disturbances. TOI-2535 b’s transits arrived up to six hours earlier or later than a simple repeating schedule predicted. Such deviations are known as transit-timing variations. They can occur when another planet exerts a gravitational pull that changes the timing of the transiting planet’s orbit.
Timing and duration measurements provide different information. A companion can alter when a planet reaches the transit point, while a change in orbital inclination alters how long the planet takes to cross the stellar disk and whether it crosses at all. The researchers combined both types of measurement with radial-velocity data from the NEID spectrograph. That combination made the companion explanation more plausible than a simple change in the star’s brightness or a measurement error, although it did not reveal the companion directly.
The hidden companion is inferred, not photographed
The team’s dynamical modelling indicates that TOI-2535 b is likely being influenced by a nearby planet with an orbital plane tilted relative to its own. The paper describes a companion that may be at least Saturn-mass and potentially in a mean-motion resonance with the hot Jupiter. A resonance occurs when orbital periods are related by a simple ratio, allowing repeated gravitational interactions to build over time.
The companion remains a hypothesis supported by the best-fitting models, not a planet that astronomers have independently imaged or seen transit its star. The paper notes that the model solutions are not exhaustive and that the companion’s precise mass and orbit remain uncertain. That distinction is essential. The observations strongly establish that the transit geometry changed; the explanation involving a neighbouring giant planet is a compelling interpretation of the timing and duration data, but it still needs further testing.
Orbital precession explains the vanishing signal
The proposed mechanism is orbital precession: the direction of a planet’s orbital plane slowly changes over time. A useful analogy is a spinning top whose axis traces a circle as it wobbles. If another massive body is inclined to the first planet’s orbit, their gravitational interaction can make the orbital planes change orientation. The planet continues to orbit its star, but the angle from which we observe it changes.
For TOI-2535 b, the precession appears to have carried the planet’s transit path beyond the edge of the star as seen from Earth. This is a striking example because the change occurred quickly enough to be tracked over a period of years. Most planetary systems evolve on timescales too long for astronomers to watch a complete change in geometry. Here, the system has provided a direct observational record of orbital evolution rather than only a theoretical prediction.
What the system may reveal about hot-Jupiter formation
Hot Jupiters have long challenged planet-formation models. Giant planets are thought to form in cooler regions of a protoplanetary disk, where ice and gas are available, yet hot Jupiters orbit extremely close to their stars. One explanation is that a giant planet moves inward gradually through interactions with the disk. Another is that gravitational interactions send it onto an elongated orbit that later circularises close to the star.
A nearby giant companion could be easier to reconcile with a slower migration path, because a planet that moved inward violently might disrupt or eject nearby worlds. The UCLA team suggests that TOI-2535 b’s architecture may favour a gradual migration scenario. That is not a final verdict on the planet’s history. The companion’s orbit is still uncertain, and other systems show that hot-Jupiter formation can involve several pathways. The value of this discovery is that it offers a rare system in which those possibilities can be tested against observed orbital changes.
Why the next transit may take decades
UCLA reported that TOI-2535 b may not transit its star again for roughly 30 to 50 years, depending on how the orbital planes continue to precess. That estimate comes from the current dynamical model, not from a scheduled event. The planet can continue to orbit its star even while its path remains outside the narrow alignment needed for a transit from Earth.
The possible companion may become visible in transit sooner if its own orbit crosses the star from our perspective. Detecting such a transit would provide a new constraint on the system and could help confirm whether the companion is responsible for the changes seen in TOI-2535 b. If no transit appears, astronomers can still use radial-velocity monitoring and further photometric observations to refine the models. The disappearance is therefore not the end of the investigation; it changes which measurements are most useful.
The role of ground-based instruments
TESS provided the long sequence of brightness measurements, but ground-based telescopes helped the team establish the system’s properties. The NEID spectrograph measures changes in a star’s radial velocity, the motion of the star towards or away from Earth. A planet’s gravity causes its star to move slightly around the system’s centre of mass, producing a periodic shift in the star’s spectrum.
The WIYN 3.5-metre telescope at Kitt Peak also contributed to the characterisation of the hot Jupiter. Combining photometry and spectroscopy is important because each method has different strengths. Transit data reveal the planet’s size relative to the star and the geometry of the crossing. Radial velocity provides information about the gravitational influence of orbiting bodies. A model that explains both data sets is more persuasive than one that fits only the disappearing light curve.
What astronomers still need to learn
The observations establish that TOI-2535 b’s transit signal changed dramatically, but several questions remain. The companion’s mass, orbital period, inclination and exact location are not yet tightly determined. The researchers will need additional radial-velocity measurements and continued monitoring to see whether the proposed gravitational configuration remains consistent with the data.
The star itself must also be characterised carefully, because changes in stellar activity can complicate transit measurements. The team’s interpretation relies on the fact that the transit durations and timing shifts fit a coherent dynamical explanation. More observations can test whether the same model predicts future behaviour. The system is valuable because it gives astronomers a chance to watch planetary architecture change rather than infer it solely from a static snapshot.
A disappearing planet becomes a new kind of observatory
The central lesson is that a planet’s absence from a transit survey can be scientifically informative. A missing dip in starlight might indicate an instrumental problem, a change in the star or a shift in the geometry of the orbit. In TOI-2535, years of data show that the transit did not simply disappear without warning. It changed gradually, and the timing variations pointed towards a gravitational interaction.
The discovery gives astronomers a rare laboratory for studying how planets influence one another over observable timescales. It may also help explain how some hot Jupiters reach their close-in orbits and why planetary systems can become tilted long after formation. The companion is still inferred rather than directly seen, so the explanation remains open to testing. But TOI-2535 b has already shown that a world can keep orbiting its star while disappearing from the particular view that made it detectable.
Frequently asked questions
Has TOI-2535 b disappeared from space?
No. It continues to orbit its star but no longer crosses the visible stellar disk from Earth’s current viewing angle.
What may have caused the transits to stop?
Researchers infer that an unseen, tilted companion is gravitationally changing the planet’s orbital plane.
When could the planet transit again?
The current model suggests roughly 30 to 50 years, but that is an estimate rather than a fixed prediction.
Sources and further reading
- UCLA, November 9, 2026
- Research paper in The Astrophysical Journal Letters, November 9, 2026
- Space.com, November 11, 2026
Featured photograph is illustrative and is not a documentary image of the reported event. Photographer and Unsplash licence details are recorded in the media-library caption and description.
