Massive Planet Found Orbiting a Tiny Star Baffles Scientists

Astronomers have uncovered a perplexing planetary pairing that’s turning conventional theories of planet formation on their head. A newly discovered gas giant — roughly the size of Saturn — has been found orbiting a star so small that, according to current models, it shouldn’t be able to host such a large companion. This curious cosmic mismatch has sent ripples through the astronomy community, forcing experts to question the limits of what’s possible in the universe.

The star, named TOI-6894, resides approximately 240 light-years away in the constellation Leo. To put that in perspective, one light-year equals about 5.9 trillion miles (9.5 trillion kilometers). While this isn’t especially distant in cosmic terms, what makes TOI-6894 remarkable is its diminutive size. It’s a red dwarf — the smallest, coolest, and most common type of star in our galaxy — with only 21% the mass of our sun and about 250 times less brightness.

What’s astonishing is the identity of its planetary partner: a gas giant almost the same size as Saturn, marking it as the largest planet ever found orbiting such a small star. In fact, TOI-6894 is about 40% smaller than the previous record-holding stars known to host large planets. The planet itself sits incredibly close to its star, completing a full orbit every three Earth days, making it a scorching world, though not quite as blistering as the infamous “hot Jupiters” found around larger stars.

In our own solar system, the sun’s diameter is ten times greater than that of Jupiter, the largest planet orbiting it. Yet in the TOI-6894 system, the size gap is far narrower — the star’s diameter is just 2.5 times larger than its planet’s. That unusual ratio leaves researchers scratching their heads.

“The question of how such a small star can host such a large planet is one that this discovery raises — and we are yet to answer,” explained Edward Bryant, an astronomer at the University of Warwick and lead author of the newly published study in Nature Astronomy.

Under the most accepted models, planetary systems form within vast molecular clouds of gas and dust. These clouds collapse under gravity to form a star, while the residual material creates a surrounding protoplanetary disk. From this disk, planets slowly coalesce. Smaller clouds naturally form smaller stars, and those stars’ disks are thought to lack the necessary material to build gas giants.

“This is because to build a giant planet, you need to quickly form a large, dense core and then rapidly accumulate gas around it before the protoplanetary disk disperses,” noted Vincent Van Eylen, an exoplanet scientist at University College London and co-author of the study. “But with smaller stars, there’s just not as much raw material or time to make this happen.” And yet, somehow, it did.

The planet’s size makes it impossible for it to be larger than its host star, but the narrow margin between the two defies the typical proportions seen elsewhere in the galaxy. No known planet is bigger than its star, but this one comes unusually close. That alone would be enough to pique astronomers’ interest, but the implications go deeper.

If a tiny red dwarf like TOI-6894 can host such a giant planet, it raises the possibility that there may be more gas giants orbiting small stars in the Milky Way than previously believed. Given that red dwarfs are the most common type of star in our galaxy, this discovery hints at a potential treasure trove of hidden worlds.

The team relied on data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Southern Observatory’s Very Large Telescope (VLT) in Chile to confirm the planet’s existence. Over the coming year, they plan to follow up with observations using the James Webb Space Telescope, aiming to unlock details about the planet’s composition and atmosphere.

Bryant suspects the planet likely has a massive rocky or icy core enveloped by thick layers of hydrogen and helium gas, but only future observations will tell for sure.