James Webb Space Telescope: Discovery of JuMBOs see free-floating planets in Orion

Dozens of planet Jupiter-sized objects are free floating in the Orion nebula, unconnected to any star.

The James Webb Space Telescope (JWST) has spotted these planets in an observation that could change the way we view astronomy.

The entities, which have been named Jupiter Mass Binary Objects or JuMBOs, are too small to be stars but defy the conventional definition of a planet as they do not orbit around a parent star.

The JuMBOs appear to be moving in pairs, and the JWST observed about 40 pairs in total. They confound existing theories of star and planetary formations.

Their existence could be explained through the objects growing out of regions in the nebula, where the density of material was insufficient to make fully formed stars. Another possibility is that they were made around stars but pushed into interstellar space via various interactions.

Prof Mark McCaughrean, a senior adviser for science and exploration at the European Space Agency (ESA), said the observations were inspired after data from ground-based telescopes pointed at the existence of the mysterious class of object.

“We were looking for these very small objects and we find them. We find them down as small as one Jupiter mass, even half a Jupiter mass, floating freely, not attached to a star,” he said. “Physics says you can’t even make objects that small. We wanted to see, can we break physics? And I think we have, which is good.”

The large, hot, gassy objects appear to be planet-like in their composition. Analysis reveals steam and methane in their atmospheres, but they are not technically planets.

“Most of us don’t have time to get wrapped up in this debate about what is a planet and what isn’t a planet,” McCaughrean said. “It’s like my cat is a chihuahua-mass pet. But it’s not a chihuahua, it’s a cat.”

The objects are around 1 million years old with infernal surface temperatures of roughly 1,000C. However, without a parent star, their temperatures will rapidly cool down. As they are gas giants, these strange worlds will not be able to harbour liquid and would not be strong contenders for hosting alien life.

The planets lie in the Orion Nebula, or M42, which is seen as the fuzzy middle “star” in the “sword” of the Orion constellation. It is 1,344 light years away but the closest region of massive star formation to Earth.

The nebula has rolling clouds of dust and gas, and when these cool they fragment and collapse under their own gravity. However, The latest observations are more challenging to explain because, out of the hundreds of roughly Jupiter-sized objects found, dozens are in binary pairs. “How can you throw two things out [of a star’s orbit] in a chaotic interaction and get them to stick back together again?” asked McCaughrean.

The findings are published as a preprint, but are yet to be peer reviewed.

Prof Matthew Bate, the head of astrophysics at the University of Exeter, who was not involved in the research, said: “I don’t know how to explain the large numbers of objects they’ve seen. It seems we’re missing something in all of the theories we’ve got so far. It seems that there’s a mechanism that’s forming these [objects] that we haven’t thought of yet.”

He added: “It’s pretty rare that this kind of discovery is made.

“In the last decade, a lot of us thought we understood star formation pretty well. So this is really a very, very surprising result and we’re going to learn a lot from it.”