In a plot twist that could make even the most seasoned sci-fi writer raise an eyebrow, a team of astronomers has discovered a giant exoplanet that, by all accounts of the cosmic rulebook, should not exist in its current location. The planet, charmingly dubbed TOI-5205b, is roughly the size of Jupiter and orbits a star so humble that no one expected it to have such glamorous company.
The planet’s host star, TOI-5205, is a cool M-dwarf star that would typically be the sort of celestial body you’d find sipping lukewarm tea at the back of the galactic retirement home. It’s about 40 percent the mass of our Sun and leagues behind in terms of star power. And yet, against all odds and several astrophysical models, here it is playing host to a gas giant that should have packed up and gone elsewhere long ago.
The findings, published recently in The Astronomical Journal, come courtesy of researchers using NASA’s Transiting Exoplanet Survey Satellite (TESS), with confirmation from a lineup of ground-based telescopes that presumably gave TOI-5205b a very judgmental once-over. The planet clocks in at 1.08 times the radius of Jupiter but orbits its unassuming star at such a close range that a year there lasts just 1.6 Earth days, which is efficient if stressful.
Now, the kicker here is that theories of planet formation strongly suggest a planet like this needs a much more robust disk of material around a bigger star to form in the first place. Essentially, TOI-5205b is like a four-tier wedding cake found mysteriously inside a budget toaster oven. As lead author Shubham Kanodia of the Carnegie Institution for Science put it, this planet “shouldn’t be there,” with the unmistakable tone of someone who double-checked the math a few too many times.
“It is a ‘forbidden’ planet,” Kanodia said, which is science-speak for “we didn’t see this one coming.”
The discovery not only shakes up existing models of planet formation around low-mass stars but also gives theorists something to furrow their brows over for the foreseeable future. They now need to explain how a star with seemingly inadequate ingredients managed to bake such an oversized planetary soufflé.
TOI-5205b may be defying formation expectations, but it appears blissfully unaware it has sent astronomers back to their chalkboards and caffeine.
Turns out, in space as in life, sometimes the underdog throws the biggest party.