Using the James Webb Space Telescope (JWST), astronomers recently discovered a new type of celestial object in the star-birthing region closest to Earth that could challenge existing theories of how planets and stars are born.

The objects found in the Orion Nebula, located around 1,350 light years from Earth and known as Messier 42 (M42), have masses similar to that of Jupiter—plus, many come in binary pairings. The scientists behind the observation of around 42 pairs of these free-floating objects not bound to stars have named them “Jupiter-mass binary objects” or “JuMBOs.”

The masses of these JuMBOs are too low to be considered stellar bodies or even “failed star” brown dwarfs, yet co-discoverer Mark McCaughrean, senior science advisor at the European Space Agency (ESA), told Popular Mechanics that just because these objects have what astronomers call “planetary masses” doesn’t mean they should be labeled planets either.

What are JuMBOs, exactly?

JuMBOs are hot and gaseous, and something entirely new—and more than a little bit weird.

This new class of celestial bodies is so strange because they can come in pairs despite having masses smaller than that of the lightest stars. That defies current binary models, which suggest that the smaller the mass of an object is, the less it should prefer company.

While around 75 percent of massive stars come in binaries, only around 50 percent of stars with the sun’s mass are found in binaries, and just 25 percent of lower-mass stars are found with a companion. Binaries systems of brown dwarfs — objects with 13 to 75 times the mass of Jupiter that are born like stars, but don’t have enough mass to trigger the nuclear fusion of hydrogen that defines a star — are vanishingly rare.

That means these objects with masses far below 13 times that of Jupiter and just below the theoretical mass of the smallest brown dwarfs — about three to seven Jupiter masses — really shouldn’t exist in partnerships, especially in such wide binaries separated by up to 300 times distance between the Earth and the sun.

“It’s extraordinary to find these at all. What we’re seeing are quite wide binaries separated by about the size of our solar system, and the frequency of wide binaries when you get to the bottom of brown dwarfs is effectively zero,” said McCaughrean, who found the JuMBOs along with fellow ESA scientist Samuel Pearson. “And yet, all of a sudden, for us, as you go to even smaller masses, it goes up to 10 percent. That’s one of the things about JuMBOs that’s really got people scratching their heads: how on earth is the binary frequency change back up?”

Nobody predicted JuMBOs

University of Exeter astrophysicist Matthew Bate, who studies the formation of stars and planets and was not involved in this discovery, is one of those aforementioned metaphorical head scratchers.

“The fact that there are free-floating planets is not a surprise, but these planetary-mass binary objects are a big surprise because nobody predicted them,” Bate told Popular Mechanics. “One or two objects, you could explain with some unusual set of initial conditions, but the fact that there’s so many of them found in Orion implies that there is quite a frequent way of forming these systems, and that’s not understood at all.”

McCaughrean thinks that there are essentially two basic possible formation mechanisms for JuMBOs, but neither of these theories are perfect as it stands.

“The first method would see JuMBOs form like the stars and brown dwarfs, from the fragmentation of a big initial cloud of gas and dust into smaller and smaller chunks,” the ESA scientists explained. “The problem is, there is a limit, which says, ‘Sorry, you can’t go past that,’ and the clouds won’t break into anything smaller. We are seeing objects that are, let’s say, ten times smaller than that limit.”

McCaughrean added that the other possibility is that JuMBOs form like planets in disks of gas and dust called “protoplanetary disks” around young stars — just like the planets of the solar system did 4.6 billion years ago — and then somehow get kicked out of these systems as a result of internal or external gravitational effects such as encounters with other star systems.

“The problem is that nobody knows how to kick two of these planetary mass objects out and have them stay stuck together,” McCaughrean said.

When considering JuMBOs, Bate has also considered the possibility they formed like planets and were then exiled from their home star system.

“It’s difficult to see how you do that for these JuMBOs because you’d have to object two Jovian mass planets almost simultaneously from the same planetary system in a way that meant they were still weakly bound together and orbiting each other,” Bate said. “Again, maybe this could happen very, very rarely, but it doesn’t seem plausible that you could do that and produce 42 of them in the Orion Nebula Cluster.”

Do JuMBOs exist elsewhere in the universe?

Bate runs simulations of star and planetary formation processes and said he has never seen anything like a JuMBOs form in those models. This means, as far as he is concerned, the discovery of JuMBOs points to a missing ingredient in our recipe of how celestial objects are born. A big question for Bate now is whether JuMBOs are unique to Orion or if we will discover them in other star-forming regions.

“There’s obviously something weird going on, and not necessarily just in Orion; it may be happening in other places,” McCaughrean said. “That is, of course, one of the things we want to do now is go until we find these objects elsewhere.”

This search outside Orion for JuMBOs could help determine if huge bright stars called the Trapezium stars, which sit at the heart of this nebula, could play a role in the formation of these strange objects. These stars could be acting as a huge “ultraviolet flashlight” in the middle of the region, blowing away star-forming gas and dust and also affecting it in such a way that allows for the creation of smaller objects than usual star formation allows.

“I’ve been looking at Orion, as I said, for 37 years or so, and I’ve tried to use the best technology to see what’s new, what the last generation of technology couldn’t see,” McCaughrean said. “But to find something I absolutely didn’t expect? That’s what we live for, as observers in astronomy, to point a telescope somewhere and see something that no other human being has ever seen before. Well, that’s kind of the dream, isn’t it?”