Scientists Astonished By Discovery of Giant Planet That Doesn't Make Any Sense: 'We Don't Understand'

After decades of analysis, scientists have a set of principles upon which they believe the universe behaves. Recently, a team of researchers analyzed a phenomenon that should not have existed by these accepted rules, as reported by Science Daily. Findings regarding this phenomenon have been published in Nature Astronomy. The phenomenon in question is a giant planet called TOI-6894b. This giant gas planet stands apart from others of its kind, as per the insights available to experts. It orbits around the red dwarf star TOI-6894, which is small in size and, according to what is known about its features, should not be able to host a giant planet. Dr Vincent Van Eylen of UCL's Mullard Space Science Laboratory, said: "It's an intriguing discovery. We don't really understand how a star with so little mass can form such a massive planet!"

The red dwarf star reportedly measures around one-fifth of the Sun's mass, according to SciTech. Such stars are common in the universe and have repeatedly been examined by experts. Researchers long believed that the star could not provide the conditions needed to support a giant planet. Contrary to all expectations, data from NASA's Transiting Exoplanet Survey Satellite (TESS) mission indicated that there was a clear signature of a giant planet orbiting TOI-6894b. Dr. Edward Bryant, Warwick Astrophysics Prize Fellow and first author, shared that he and his team considered TESS observations associated with around 91,000 low-mass red dwarf stars and readings undertaken by ESO's VLT telescope for this study. They were elated by the finding and believe it will help experts understand several hidden aspects of planet formation. 

Researchers have identified TOI-6894b to be a low-density gas planet. According to the retrieved data, the body's radius is slightly larger than Saturn's, but its mass is just half of the second-largest planet in the solar system. The existence of TOI-6894b implies that TOI-6894 is the lowest mass star discovered to date, hosting a transiting giant planet. The next smallest star that is known to host a transiting planet in the universe is 60% larger than the mass of TOI-6894. Experts did not think that a star with such low density could form or support a planet, as it supposedly could not fulfill the requirements of popular methods believed to be responsible for creating giant planets.

One of these methods is core accretion theory, which speculates that a planet is formed due to the accumulation of material, followed by the drawing of gas. The involvement of the latter facilitates an atmosphere and slowly causes the body to transform into a gas giant. Such a process cannot occur with a low-density star like TOI-6894, as it supposedly cannot provide the gas and dust needed to build a planet's core. The existence of TOI-6894b indicates that the speculated process is possibly not correct. There are some steps or aspects that experts believe are missing from their side about the planet formation.

Another possible theory of planet formation is due to a gravitationally unstable disc. Here, the orbit around the Sun becomes unstable because of the gravitational force acting on it and breaks down. After the breakdown, it separates into fragments, facilitating the collapse of gas and dust to form a planet. According to the available data, this theory could also not explain the formation of TOI-6894. However, researchers are not completely rejecting the possibility of these processes. TOI-6894b also stands apart from other exoplanets in several features. It is colder than other gas giants found to date, exhibiting a temperature of just 420 Kelvin. This insight indicates that it has a methane-dominated atmosphere and could also contain ammonia, which has never been detected in exoplanets. 

 "TOI-6894b likely presents a benchmark exoplanet for the study of methane-dominated atmospheres and the best 'laboratory' to study a planetary atmosphere containing carbon, nitrogen, and oxygen outside the Solar System," Professor Amaury Triaud, University of Birmingham, co-author and member of the SPECULOOS collaboration, said. Dr. Daniel Bayliss, Associate Professor at The University of Warwick, claims that if such a small star can form and support a planet, this could mean many more giant planets in a similar system could exist in the universe. Researchers are hopeful that they will gain more insights regarding the exoplanet when it is observed by the James Webb Space Telescope (JWST) in the next 12 months.

For more information, you can read the study, A transiting giant planet in orbit around a 0.2-solar-mass host star. Nat Astron (2025), published by Bryant, E.M., Jordán, A., Hartman, J.D. et al. in Nature.com journal.