Astronomers have solved the puzzle of an exoplanet that seemingly disappeared from view for seven years. New research suggests the planet, TOI-2535 b, didn’t vanish but was dramatically tugged out of its observable orbit by an unseen celestial neighbor.
Located approximately 1,000 light-years from Earth, TOI-2535 b orbits its host star every 8.25 days. This rapid orbit, nearly 10 times faster than Mercury’s orbit around our Sun, classifies it as an extremely hot planet, often referred to as a “hot Jupiter.” NASA’s Transiting Exoplanet Survey Satellite (TESS) monitored the exoplanet from April 2019 to March 2026.
However, during this observation period, peculiar anomalies emerged: TOI-2535 b’s orbit became erratic. The planet was frequently detected arriving up to six hours earlier or later than predicted. Then, in March of this year, TESS stopped registering the characteristic dip in the star’s brightness caused by TOI-2535 b passing in front of it, a phenomenon known as a transit. The planet had effectively vanished from the TESS data.
An Invisible Neighbor and Cosmic Choreography
By analyzing the TESS data, a research team concluded that TOI-2535 b is under the influence of an invisible companion planet. This unseen world is also gravitationally affected by TOI-2535 b, leading to orbital “wobbles” for both bodies within the TOI-2535 system. The apparent disappearance of TOI-2535 b occurred because these orbital shifts tilted its path, moving it out of the plane required for TESS to detect its transits.
“We’re used to thinking of the universe as a clockwork mechanism, where everything happens on schedule, but that’s not the case,” explained team member Samuel Yee from the University of California, Los Angeles. “If you have multiple planets in a system, they can affect each other’s orbits. We know of several such systems. This is the most extreme example we’ve seen yet, where two planets are interacting so strongly. The planet’s orbit is tilting so rapidly that its transit just disappeared before our eyes.”
A New Theory on ‘Hot Jupiter’ Formation
The formation of planets like TOI-2535 b remains a subject of much debate. Current theories suggest such planets need to form with abundant ice. Given that ice is unlikely to be plentiful so close to a star, “hot Jupiters” are thought to form much farther away and then migrate inward.
Two primary migration pathways are considered:
- A planet could be thrown into an elliptical orbit by strong gravitational interactions, perhaps a close encounter with another planetary object, before stellar interactions draw it closer.
- A “hot Jupiter” might be pulled inward along with other planets within the flat disk of gas and dust surrounding a young star, known as a protoplanetary disk.
If the second, less tumultuous pathway leads to the inward migration of “hot Jupiters,” the resulting planetary system would typically be very flat, with minimal tilting between planetary orbits. However, the tilt induced by TOI-2535 b’s unseen neighbor indicates that even flat systems can be perturbed by later, more inclined orbits.
“Since TOI-2535 b has a close neighbor, it probably migrated by slowly spiraling in, rather than being flung in,” Yee noted. “We might be observing a formation channel that doesn’t happen very often, but it’s extremely interesting.”
The team’s findings have been published in The Astrophysical Journal Letters.
