Speaking of hot worlds, a newly discovered exoplanet has provided an extreme case of an ultrahot Jupiter. Because we needed more ways to compare exoplanets to Jupiter, I guess.

Found using data from NASA’s TESS spacecraft and reported in The Astronomical Journal, exoplanet TOI-2109b has dayside temperatures estimated to be about 3,500 Kelvin or 3,200˚ Celsius. That makes this gas giant as hot as a small star and the second hottest planet ever discovered. The hottest exoplanet? Dr. Pamela’s favorite, KELT-9b, comes in at a vaporizing 4,300 degrees Celsius.

Of course, one of the defining characteristics of hot Jupiters is the length of their orbit, which is generally less than ten Earth-days because these worlds are incredibly close to their parent stars. TOI-2109b is no exception and in fact, has the shortest known orbit at just 16 Earth hours. Hours. Not days but hours. Oof. I cannot imagine the speed of the winds on that world. And in addition to being super fast, super close, and super hot, this gas giant is about five times the mass of Jupiter.

What’s really interesting about this particular planet is that astronomers think TOI-2109b is in the process of spiraling in toward its star. The orbit is decaying, and the already shortened orbit is accelerating the planet’s inward movement. Since that decay could be happening quickly, astronomers may be able to witness and study a little of the decay behavior in real-time. Lead author Ian Wong notes: In one or two years, if we are lucky, we may be able to detect how the planet moves closer to its star. In our lifetime we will not see the planet fall into its star. But give it another 10 million years, and this planet might not be there.

Okay, so we’re not going to watch a planet crash and burn, but still, that’s a pretty exciting discovery and observation to make. We’ll learn a lot from this ultrahot Jupiter, and we’ll bring it to you here on Daily Space.

More Information

MIT press release

“TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit,” Ian Wong et al., 2021 November 23, The Astronomical Journal