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On October 2, 2023, scientists at the European Space Agency (ESA) announced the discovery of free-floating entities in the Orion Nebula that are too small to be stars but defy conventional models of planet formation. The objects have been named Jupiter-Mass Binary Objects (JuMBOs) because out of the hundreds of planet-like objects identified, dozens came in pairs. They were observed in images taken by the James Webb space telescope (JWST) and are described in two papers from Prof Mark McCaughrean (Senior Advisor for Science & Exploration at the European Space Agency) and Dr Samuel Pearson. The papers, which have been submitted to journals but have not been peer-reviewed at the time of release, were released at the same time of ESA's image release following the JWST's near-infrared survey of the Trapezium Cluster & inner Orion Nebula.
JuMBOs appear to be a smaller class of gaseous objects that are planet-like in their composition. Data shows steam and methane in their atmosphere. Observed JuMBOs are roughly 1 million years old with a surface temperature of around 1,000oC. Without a host star, JuMBOs will rapidly cool, and although they will briefly exhibit temperatures in the range of habitability, they are gas giants, and their surfaces could contain liquid water. This means they are not strong candidates for hosting alien life. The binary pairs are separated by roughly 200 astronomical units (distance between the Earth and the Sun), orbiting each other in paths that take more than 20,000 years to complete.
Examples of what scientists believe to be JumBOs in the Orion Nebula.
The discovery of JuMBOs seems to conflict with leading theories of star and planetary formation, which suggest it is not possible to form Jupiter-sized objects through the same process of star formation inside clouds of dust and gas in a nebula. Stars form when dust and gas clouds cool, progressively fragment, and collapse under their own gravity. The smallest observed stars have a mass roughly 80x that of Jupiter. Below this threshold, the core is not dense enough to fuse hydrogen. Smaller objects, known as brown dwarfs (sometimes referred to as failed stars), can coalesce through the same process. But theoretical predictions suggest the lower boundary of an object forming through a star-like gravitational collapse is between three to seven Jupiter masses.
Smaller free-ranging objects have been observed. However, it is unclear whether they formed in situ or were ejected from a planetary disc around another star. The latest observations of dozens of binary objects challenge the idea that they were ejected out of a star's orbit Forty-two pairs have been observed by the Webb telescope in the Orion Nebula. Current scientific models cannot explain how single small objects are formed directly from clouds of dust and gas, let alone pairs. If they were ejected planets, kicked from young star systems in a chaotic interaction, it is unclear how there would be so many binary objects.
Messier 42 or the Orion Nebula is 1,344 lightyears away, located in the belt of the northern hemisphere constellation of Orion. It has long been studied by astronomers as the closest region to Earth with significant star formation to Earth. At the core of the Orion Nebula is the Trapezium Cluster of stars, the largest of which illuminate the surrounding gas and dust with their intense ultraviolet radiation fields. The nebula contains a rich diversity of phenomena and objects, including:
- Outflows and planet-forming disks around young stars
- Embedded protostars; brown dwarfs
- Free-floating planetary mass objects
- Photodissociation regions
The discovery of JuMBOs comes from new imaging of the Orion Nebular using JWST's near-infrared camera, NIRCam. Prof Mark McCaughrean stated the observations were inspired after data from ground-based telescopes hinted at the existence of the mysterious class of object. Dr Pearson stated they hope to use the Webb telescope to observe existing JuMBOs in closer detail (revealing their gaseous atmospheres and better understanding how they were formed) as well as look for new JuMBOs in other star-forming regions.
