Since astronomers found that there were planets around other stars, there has been a big effort to locate these exoplanets and learning what we can about them. These planets are, after all, where life will exist if it is out there at all.

So far, researchers have confirmed just over 6100 planets beyond our solar system. Out of the trillions that almost certainly exist in the Milky Way, and countless more in other galaxies, that is the tiniest fraction of all that there is to find.

Even with such a small number of planets, however, they have found that there is a lot of diversity in what planets can be like. Even within our own solar system, we know that they can range in size from smaller than our moon up to the size of Jupiter, which is 318 times as massive as Earth.

Once you start looking at planets outside of our solar system, things get even weirder. Astronomers recently submitted a paper for publication to the AAS journals about a particularly interesting example. The paper is available on arXiv.

In the paper, researchers look at the planet TOI-4507 b. This interestingly named planet is about the size of Jupiter, but it has a mass that is much less than Saturn’s.

Compared to Earth, this planet weighs just 30 times more. Compared to Jupiter, which is 318 times as massive, it is easy to see that this planet has a very low density. Because of this, it is called a ‘super puff’ planet, or sometimes a ‘marshmallow planet.’

TOI-4507 b is not the first planet like this. Normally, they orbit near their stars, which causes them to be very hot. The heat expands the planet to be quite large for its mass.

This one, however, is much further away from its star. In the paper, the authors wrote:

“[W]e present the discovery and characterization of TOI-4507 b, a cold planet transiting a young F star with an orbital period of 105 days. Our observations reveal that the planet has an unusually low density, making it one of the longest-period super-puffs known to date.”

A planet this far away from its star would likely be much colder, so there isn’t an easy explanation for why it has such a low density.

Of course, it is difficult to accurately measure planets that are so far away. The authors of the study admit that it is possible that what their instruments are measuring is actually the rings around the planet rather than the planet itself.

Researchers are hoping that additional data can be gathered about the planet when it is observed again by the James Webb Space Telescope and other instruments in the future.

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