Astronomers have discovered that a distant giant planet, known as TOI-2109b, is in a dramatic death spiral, slowly falling toward its star in a fiery end that could help unlock secrets about how planets and stars interact.
The planet is located about 870 light-years from Earth and is one of the most extreme exoplanets ever observed.
TOI-2109b is called an “ultra-hot Jupiter” because it’s a gas giant like Jupiter, but it’s much hotter and orbits extremely close to its star.
In fact, it completes one full orbit in just 16 hours—making it the fastest-orbiting gas giant ever found. For comparison, Mercury, the closest planet to our sun, takes 88 days to complete one orbit.
TOI-2109b is not only bigger and heavier than Jupiter—it’s about five times Jupiter’s mass and nearly twice its size—but it also orbits its star much more closely than Mercury orbits the sun.
The international research team, led by Dr. Jaime A. Alvarado-Montes from Macquarie University, analyzed data from NASA’s TESS mission, the European Space Agency’s CHEOPS satellite, and several ground-based telescopes collected over more than a decade.
They found that the planet’s orbit is shrinking slightly over time, by about 10 seconds every few years. This means TOI-2109b is slowly spiraling inwards toward its star.
Scientists believe this death spiral could end in one of three ways: the planet might be ripped apart by the intense gravitational forces of the star, it might crash directly into the star, or it could lose its outer layers of gas and leave behind only a rocky core.
This situation is not just a cosmic curiosity—it could help answer some big questions in astronomy.
For instance, some rocky planets seen in other solar systems may actually be the leftover cores of giant planets like TOI-2109b that had their atmospheres stripped away. Watching this process unfold in real time could give scientists valuable insights into how planets form, evolve, and sometimes die.
“This planet and its extreme orbit offer a rare chance to study a planetary system on the edge of destruction,” said Dr. Alvarado-Montes. “What we learn from it could help explain the origins of many other planets across the galaxy.”
Over the next few years, continued observation of TOI-2109b’s slow but steady fall may help scientists uncover long-standing mysteries about the life and death of planets.
