One nice thing about discovering exoplanets is that, once you work out how long their orbits take, they continue to show up like clockwork. The timing is so regular, in fact, that we can use variations to detect the gravitational influence of additional planets in the same exosolar system. And the precise timing is useful in that we can rely on it to point telescopes at the system when we know some of the light we detect has passed through the planet’s atmosphere.
On Monday, researchers reported on an exoplanet that simply stopped showing up. TOI-2535b is a hot Jupiter-sized planet we’ve been observing as it transits between its host star, TOI-2535, and Earth for about seven years now. But it recently stopped showing up, and researchers suspect that’s due to an unseen companion orbiting in a different plane.
TOI-2535 is one of the many stars with exoplanet candidates identified by TESS, the Transiting Exoplanet Survey Satellite. It’s a K dwarf, meaning it’s somewhat smaller than the Sun. And TESS found signs of a Jupiter-sized planet orbiting it every eight days, an orbit close enough to make TOI-2535b a “hot Jupiter” exoplanet. At that point, there was nothing especially unusual about it.
But a closer look at the data showed two very strange things. First, the timing of when its transits occurred could shift by as much as six hours, a substantial variation for an orbit this brief. That’s typically a sign of gravitational interactions with another planet; depending on the details of that second planet’s orbit, it may slow the first one or accelerate it through a transit more quickly. Since the second planet doesn’t show up in TESS data, it appears to orbit in a slightly different plane, so it doesn’t pass between its host star and Earth.
