Level 1 — Absolute Beginner
Far from Earth, there is a star with a giant planet. The planet is big and hot, like a very hot Jupiter. Its name is TOI-2535 b.
A space telescope called TESS watched this star for seven years. Again and again, the planet moved in front of the star. Then the star looked a little darker for a short time.
But something strange happened. Each year, the dark time became shorter. In 2026, it did not come at all. From Earth, the planet was gone.
Scientists say the planet is still there. They think a second planet is near it. We cannot see this second planet, but it pulls on the first one. Now the path of the hot planet is tilted, so it does not pass in front of the star for us.
- star
- A huge ball of burning gas in space, like the Sun.
- giant
- Very big.
- planet
- A large round object that moves around a star.
- telescope
- A tool for looking at things that are very far away.
- darker
- With less light.
- strange
- Unusual and hard to explain.
- pulls
- Moves something toward itself.
- tilted
- Leaning to one side, not straight.
Level 2 — Elementary
Astronomers have watched a planet disappear from view, and they believe they understand the reason. The planet, TOI-2535 b, is a 'hot Jupiter', a huge ball of gas that travels very close to its star. It is about 1,000 light-years from Earth.
NASA's TESS satellite first observed it in 2019. At that time, the planet crossed the middle of its star again and again, and each crossing blocked a little of the star's light. Astronomers call such a crossing a transit, and they use transits to find planets.
Over the next years, the transits changed. Sometimes they came up to six hours early or late. They also became shorter and weaker. When TESS looked again in early 2026, there was no transit at all.
A team led by Samuel Yee at the University of California, Los Angeles, studied seven years of measurements. The team says a hidden neighbour, at least as heavy as Saturn, is pulling on the planet. The pull makes the planet's orbit wobble like a spinning top, so the planet now passes above or below the star when we look from Earth. It is the first time anyone has confirmed this for a planet around a single star.
- disappear
- To stop being seen.
- light-years
- Units of distance equal to how far light travels in one year.
- satellite
- A machine that travels around Earth or another body in space.
- observed
- Watched something carefully.
- transit
- The movement of a planet across the face of its star.
- neighbour
- Something that is next to or near another thing.
- orbit
- The curved path of a planet around a star.
- wobble
- To move from side to side in an unsteady way.
Level 3 — Intermediate
A giant planet that astronomers had tracked for seven years has stopped crossing the face of its star, in what researchers describe as the first confirmed case of vanishing transits for a planet orbiting a single star. The planet has not gone anywhere. Instead, according to a team led by Samuel Yee of the University of California, Los Angeles, its orbit has tipped out of our line of sight.
The object, TOI-2535 b, is a hot Jupiter roughly 1,000 light-years away. When NASA's Transiting Exoplanet Survey Satellite, known as TESS, first recorded it in 2019, the planet passed almost directly across the centre of the stellar disc. That is the geometry planet hunters depend on, because each transit dims the star by a small, measurable amount.
Follow-up observations from TESS and from telescopes on the ground revealed increasingly odd behaviour. Transits did not keep to a regular timetable, arriving as much as six hours ahead of or behind schedule. They also grew shorter and shallower year after year, a sign that the planet was skimming ever closer to the edge of the disc. By early 2026 the dips had ceased entirely. The team says it is the fastest change of this kind recorded for such a system.
The explanation the researchers favour is a second planet, with at least the mass of Saturn, whose gravity makes the first planet's orbit precess, or wobble, like a top. Nobody has detected that companion directly yet. Its existence would itself be surprising, because hot Jupiters are generally thought to be solitary, with no close neighbours. The study, titled 'A TESS Disappearing Act', has been posted on the arXiv preprint server.
- tracked
- Followed the movement or progress of something.
- line of sight
- The straight line between an observer and the thing observed.
- geometry
- The arrangement of objects in relation to each other.
- dims
- Makes less bright.
- shallower
- Less strong, with a smaller drop.
- ceased
- Stopped.
- precess
- To slowly change the direction of a spinning or orbiting motion.
- solitary
- Alone, without companions.
Level 4 — Advanced
Exoplanet astronomy is built on a simple wager: that a world which crosses its star today will cross it again tomorrow. TOI-2535 b has broken the bargain. In a preprint posted to arXiv under the wry title 'A TESS Disappearing Act', Samuel Yee of the University of California, Los Angeles, and colleagues document how the transits of this hot Jupiter, some 1,000 light-years distant, dwindled over seven years and then stopped. It is, they argue, the first confirmed instance of a planet around a single star slipping out of transit, and the most rapid such evolution on record.
The chronology is unambiguous. In 2019 NASA's TESS spacecraft caught the planet traversing the star near the centre of the disc. Subsequent sectors of TESS data, supplemented by ground-based photometry, showed the events arriving erratically, as much as six hours adrift of prediction, while contracting in both duration and depth. By the time the satellite returned to the field in early 2026 the light curve was flat.
Planets do not evaporate on that timescale, so the authors look to dynamics. Their preferred model invokes an unseen companion of at least Saturn's mass whose gravitational torque causes the orbital plane of TOI-2535 b to precess, much as a spinning top traces a slow circle with its axis. As the plane swings, the planet's apparent track climbs toward the stellar limb and finally misses the disc altogether. The same perturbation neatly accounts for the timing anomalies that preceded the disappearance.
If the companion is real, it complicates a tidy piece of received wisdom. Hot Jupiters have long been regarded as loners, their violent migration inward presumed to scatter or swallow any nearby siblings. A hefty neighbour close enough to tilt the orbit within a decade would be an awkward exception, and a valuable one for theorists of planetary formation. The result also carries a cautionary corollary for the field at large: transit surveys offer only snapshots of systems that are quietly shifting, and some known planets may be drifting out of view, while others drift into it, without anyone noticing. Confirmation will require detecting the perturber itself, probably through precise measurements of the star's motion.
- wager
- A bet or gamble.
- dwindled
- Became gradually smaller or weaker.
- erratically
- In a way that is not regular or predictable.
- photometry
- The measurement of the brightness of stars and other objects.
- torque
- A force that causes something to turn or twist.
- perturbation
- A small change in motion caused by an outside force.
- anomalies
- Things that differ from what is normal or expected.
- corollary
- Something that follows naturally from a result.
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