Follow us Add us as a preferred source on Google Newsletter Subscribe to our newsletter Astronomers have solved the mystery of an extrasolar planet, or exoplanet, that “disappeared” after seven years of observations. New research suggests that the planet has not disappeared at all, but has been dragged out of its orbit by an unseen planet. The exoplanet, called TOI-2535 b, is about 1,000 light years away. TOI-2535 b was routinely observed with NASA’s Transiting Exoplanet Survey Satellite (TESS) space telescope for seven years, between April 2019 and March 2026, as it completed its 8.25 Earth-day orbit of its parent star. That’s 10 times faster than Mercury’s orbit around the Sun and means this incredibly hot planet is classified as a “hot Jupiter.” However, something strange began to happen when astronomers looked at the distant world. The planet’s orbits were not regular like those of other planets, and TOI-2535 often arrived six hours earlier or six hours later than astronomers expected. Then, in March of this year, TESS was no longer detecting the characteristic starlight dips that TOI-2535 b caused as it crossed or “transited” the face of its parent star. It seemed to have disappeared. This team used data from TESS to determine that TOI-2535 b is being attracted to an unseen neighbor and, in turn, is also attracting that planet. This is causing the orbits of both worlds in the TOI-2535 system to “wobble.” TOI-2535 b disappeared when that wobble misaligned it with its star. “We think of the universe as resembling a clock mechanism, where everything is regular, but that’s not true. If there are multiple planets in a system, they can affect each other’s orbits. We know some systems that are like that,” team member Samuel Yee of the University of California, Los Angeles, said in a statement. “This is the most extreme example we’ve seen because the two planets interact so strongly. The planet’s orbit is tilting so rapidly that its transit disappeared while we were observing.” TOI-2535 b may not be expected to transit its parent star for at least 30 years, but the hidden neighbor pulling it may cross the star’s face sooner. In the meantime, scientists will try to decode what this extremely wobbly exoplanet system says about how it formed. Hot Jupiters Should Be Interesting CustomersThere is currently a lot of speculation about how hot Jupiter planets like TOI-2535 b form. This is because current planet formation pathways suggest that planets like this would have to form around a lot of ice. Obviously, ice is not likely to be abundant as close to a star as it currently is TOI-2535 b. This means that hot Jupiters probably form far from their stars and then migrate inward. There are two ways this could happen. The planet could be excited into an elliptical orbit by violent events such as a near collision with another planetary object, and then interactions with the star push the planet inward. Alternatively, hot Jupiter may be pulled inward along with the other planets while lying in a flattened cloud of gas and dust around the young star called a protoplanetary disk. What to read next An illustration of the 10 hot Jupiter exoplanets studied with the Hubble and Spitzer space telescopes. (Image credit: NASA/ESA) If this second, less turbulent route occurs to bring hot Jupiters closer to their stars, then the resulting system should be very flat. In other words, there should be no extreme inclinations between the orbits of the planets in that system. However, the tilt caused to TOI-2535 b by its unseen companion indicates that flattened systems may be warped by more inclined orbits later in their existence. This makes slower migration possible despite orbital inclination. “Because TOI-2535 b has a close neighbor, it probably migrated by slowly spiraling rather than being thrown around,” Yee said. “We may be seeing a training pipeline that doesn’t happen very often but is very interesting.” The team’s research was published Monday (Nov. 9) in the Astrophysical Journal Letters.
