Planets come in all sizes, but some discoveries have completely blown away expectations. In 2025 alone, astronomers have confirmed massive worlds that were thought to be unlikely, or even impossible, under current theories. From giant gas giants orbiting tiny stars to “cotton candy” planets fluffier than Jupiter, these recent finds are reshaping what we thought was possible. Here are some of the biggest planetary surprises right now.
A Saturn‑sized giant orbiting a tiny red dwarf
This gas giant, known as TOI-6894b, is just a bit bigger than Saturn but orbits a star barely one-fifth the size of our Sun. That red dwarf is known as TOI-6894. It shouldn’t be possible, based on what scientists previously believed about how planets form around small stars. It’s not just its size, but its tight orbit, just three days, that has astronomers rethinking what kind of planets can form quickly, and how early in a star’s life that can happen.
A rock-heavy planet that’s practically solid iron
This planet, known as Gliese 367 b, is about the same width as Neptune, but has nearly the mass of Saturn—meaning it’s incredibly dense. It’s got nearly 10 times Earth’s gravity and is likely made mostly of iron, like a supersized version of Mercury. Planets this big and this dense are rare, and they don’t fit neatly into current models. It’s a reminder that rocky planets aren’t always small.
A fluffy planet bigger than Jupiter, but lighter
Roughly 50% larger than Jupiter, this planet, WASP-193b, is one of the lightest ever found. Its density is so low that scientists compare it to cotton candy. It’s huge, but it barely has any weight for its size. It’s also extremely puffy, likely made of mostly gas, and sits far enough from its star that it shouldn’t be this inflated. Nobody’s entirely sure how it formed, or how it stays like that.
A young planet spotted by the James Webb Space Telescope
One of the first smaller gas giants directly imaged by JWST, this Saturn-sized planet, TWA 7 b, was found orbiting a red dwarf about 34 light-years away. It’s cool, dim, and surrounded by a dusty disk—just the kind of system astronomers are eager to study right now. This one is interesting not just because of its size, but because it proves we’re now able to spot smaller, colder exoplanets directly—something that wasn’t possible just a few years ago.
A giant planet with almost no weight
WASP-17b is close in size to Jupiter, but has a mass less than 50 Earths. That gives it an extremely low density, basically just a bloated gas shell with almost no substance inside. It’s currently the largest planet known under that 50 Earth mass cutoff, and it’s helping researchers understand what makes planets grow huge without gaining much weight.
A dense, compact planet on the edge of becoming a star
This planet is slightly larger than Jupiter but far denser—so dense that it’s almost considered a brown dwarf. Known as AT2021uey b, it’s teetering on that fine line between massive planet and failed star. What makes it so interesting is that it shows not all big planets are light and fluffy. Some are small tanks, crammed full of heavy elements and metal cores. It’s a reminder of just how diverse planets can be.
What’s so cool about these discoveries?
What’s going on in space is notable for a variety of reasons. For one thing, these discoveries break the rules we thought applied to planetary formation. They show also that planets can be more extreme—larger, fluffier, or denser—than expected. Plus, they give us a clearer picture of what might exist out there, beyond the neat categories we’ve been using. In other words, they’re pretty incredible.