The planet, identified as TOI-2535 b, belongs to a class of exoplanets known as hot Jupiters. These are enormous gas giants comparable to Jupiter but orbit much closer to their parent stars, resulting in extremely short orbital periods and intense temperatures.
TOI-2535 b completes one orbit around its star in just 8.25 days. For comparison, Mercury, the closest planet to our Sun, takes approximately 88 days to complete its orbit. Despite its rapid movement, the distant planet caught astronomers’ attention for a different reason: its transits gradually changed before disappearing altogether.
Researchers tracked the planet passing across its star several times over a period of years. However, the timing of these events became increasingly irregular, while the planet’s apparent size during each transit seemed to shrink. By 2026, the expected transits had stopped.
The explanation, according to the research team, involves the gravitational influence of another planet in the same system. The two worlds are interacting so strongly that their orbital paths are changing, causing TOI-2535 b to move out of the line of sight between Earth and its star.
The discovery offers astronomers an unusual opportunity to study how planets influence one another and how giant worlds migrate towards their host stars.
How Astronomers First Detected the Planet
The discovery was made using observations from NASA’s Transiting Exoplanet Survey Satellite, better known as TESS. The space telescope examined the star TOI-2535 multiple times between April 2019 and March 2026, collecting measurements that eventually revealed the unusual behaviour of its planetary companion.
TESS searches for exoplanets by monitoring the brightness of distant stars. When a planet crosses directly between its star and the telescope, it blocks a small portion of the star’s light. This produces a temporary dip in brightness known as a transit.
Astronomers use these repeated changes to identify planets and calculate important details about their orbits, including how long they take to circle their stars.
In the case of TOI-2535 b, however, the observations did not follow the predictable pattern normally associated with planetary systems. Rather than crossing its star at consistent intervals, the planet appeared to transit either earlier or later than expected.
The timing differences reached as much as six hours, suggesting that something was disturbing its orbit. Researchers also noticed that the transits were becoming progressively shorter and less pronounced over the years.
Eventually, the planet stopped producing detectable transits in the observations collected in 2026.
Instead of concluding that the planet had disappeared physically, the researchers examined how its orbit might have changed. Their analysis pointed towards the gravitational influence of a neighbouring planet whose orbital plane is tilted relative to that of TOI-2535 b.
The two planets are effectively disturbing each other’s movements. Their gravitational interaction causes their orbital orientations to shift, changing the angle from which astronomers observe them. As a result, a planet that once crossed directly in front of its star can gradually move outside the viewing alignment required for a transit.
A Planet That Vanished While Scientists Were Watching
Samuel Yee, a 51 Pegasi b Postdoctoral Fellow at the University of California, Los Angeles, and the study’s corresponding author, said the discovery challenges the idea that planetary systems operate with perfect regularity.
“We think of the universe as resembling clockwork, where everything is regular, but that’s not true,” Yee explained.
He noted that planets within the same system can exert gravitational forces on one another, changing their orbital paths. Although astronomers have identified other systems where planets interact in this way, TOI-2535 is particularly unusual because the gravitational influence appears exceptionally strong.
According to Yee, the planet’s orbital tilt is changing so quickly that researchers were able to observe its transit disappear during the monitoring period.
The event is especially significant because astronomers rarely get the opportunity to watch such a dramatic orbital change unfold over a relatively short period.
The researchers estimate that TOI-2535 b may not transit its star again for another 30 to 50 years. Its hidden planetary companion, however, could potentially become visible sooner, offering another opportunity to investigate the system.
What the Moon Can Teach Us About the Disappearing Planet
To explain why the planet has vanished from view, the researchers compared the situation with the relationship between the Earth, Moon and Sun.
If the Moon’s orbit around Earth were perfectly aligned with Earth’s orbit around the Sun, solar and lunar eclipses would occur every month. However, because the Moon’s orbital plane is tilted, eclipses happen only when the three bodies reach the correct alignment.
The same basic principle applies to TOI-2535 b. The planet has not necessarily stopped orbiting its star. Its changing orbital orientation simply means that it no longer passes directly across the star from Earth’s viewpoint.
UCLA astrophysicist Erik Petigura, a co-author of the research, used the Moon’s orbital tilt to illustrate the phenomenon. He also pointed out that the Moon’s current orbit preserves evidence of its violent formation history, which involved a massive collision with the early Earth.
The researchers believe the unusual arrangement of the TOI-2535 system could similarly reveal important information about how its planets formed and evolved.
Why the Discovery Matters for Hot Jupiter Research
Hot Jupiters have been discovered around hundreds of distant stars, but TOI-2535 b appears to have an unusual feature: a nearby planetary companion massive enough to influence its orbit significantly.
That makes the system particularly valuable for investigating one of the biggest questions surrounding these giant worlds: How do planets that form farther away end up orbiting extremely close to their stars?
One proposed explanation is that a giant planet experiences gravitational disturbances from another object, sending it into a highly elongated, or elliptical, orbit. Over time, its path may change until it settles into a much closer orbit around its host star.
Another possibility involves planets moving alongside the gas and dust surrounding a young star. This material, known as a protoplanetary disc, provides the environment in which planets develop. Interactions with the disc can gradually influence their movements and bring them closer to their star.
However, this second process would generally be expected to produce a relatively flat planetary system, with planets orbiting in similar planes.
The tilted orbits observed in TOI-2535 suggest that gravitational interactions between objects may have played a more complicated role in shaping the system.
Yee believes the presence of a close planetary neighbour makes it more likely that TOI-2535 b migrated gradually towards its star rather than being violently thrown into an inward trajectory.
“Because TOI-2535 b has a close neighbour, it probably migrated by slowly spiraling in instead of getting flung in,” he said.
He added that the system could represent a relatively uncommon but scientifically interesting route through which hot Jupiters form.
For astronomers, TOI-2535 b is more than a planet that has seemingly disappeared. It is a rare example of a planetary system changing in real time, providing clues about the gravitational forces that shape worlds and determine where they eventually orbit.
