About 578 light-years away from Earth, astronomers recently uncovered a planet that’s rewriting what we thought we knew about worlds beyond our solar system. Meet TOI‑4507 b — a giant ball of gas that defies nearly every rule we’ve developed for how planets form and evolve.
First, let’s talk numbers. TOI-4507 b orbits a star that’s only about 700 million years old. In cosmic terms, that’s a toddler. Yet around this young star it revolves in roughly 105 days, and despite being about the size of Jupiter, it has less than one-tenth of Jupiter’s mass. In fact, its density is extremely low — it falls into a rare class called “super-puffs”, planets that are huge in volume but startlingly light.
Because its radius is so large and mass so small, TOI-4507 b’s average density is under ~0.3 g/cm³. To put that in perspective: that’s lighter than many solids, comparable to a foam or fluffy substance — if you could somehow drop it into water, in theory it would float (though obviously it’s too big and far away for that to happen).
What makes this planet even more remarkable is its orbit. It lies on what scientists call a nearly polar orbit, meaning it swings around its star in a direction almost perpendicular to the star’s equatorial plane. It’s an unusual configuration and one that raises questions about how this system formed in the first place.
Given its youth, huge size and tiny mass, astronomers are scratching their heads: how did this planet come to be? Some of the hypotheses include:
It might have formed far from its star in a cool region where gas envelopes can balloon up, then migrated inward.
It could be inflated because of internal or external heating, although in this case its distance from the star might make that less likely.
Alternatively, what looks like a giant puffed-up planet might actually be a more normal planet cloaked by an enormous ring system making it appear bigger than it is. Some researchers consider this possibility.
Why does this matter? For one thing, TOI-4507 b is a valuable laboratory. Because its atmosphere is so inflated and the star is relatively young and bright, the planet is an excellent target for follow-up observations. Instruments like the James Webb Space Telescope (JWST) could probe its atmosphere, helping scientists understand how super-puffs form, how they survive so close to their stars, and whether they lose mass quickly.
Secondly, it challenges the standard models. Usually, giant planets close to their stars experience strong stellar radiation that strips away gas and shrinks them over time. Yet here we have a very young system with a huge, light planet intact. That suggests our theories about planet formation — especially how gas envelopes are acquired, retained or lost — may need a rethink.
In simpler words: TOI-4507 b is like a giant bubble that somehow formed and floated intact next to a young star when classic models say it should have collapsed, gotten stripped or never grown that big in the first place.
As our search for worlds beyond Earth continues, discoveries like this remind us of the universe’s ability to surprise. TOI-4507 b doesn’t fit neatly into any category we have — and that’s exactly what makes it exciting.
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Source:
“Strange ‘puffy’ alien world breaks every rule for how planets should behave” – Space.com, Paul Sutter, 14 Oct 2025.
“A Cold and Super-Puffy Planet on a Polar Orbit” – arXiv pre-print, Espinoza-Retamal et al., 30 Sept 2025.
Exoplanet database entries for TOI-4507 b.