Swiss researchers solve the mystery of planet density

28 June 2024 12:08

Swissmem SSIGGreater Geneva Bern

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Bern/Geneva - Researchers from NCCR PlanetS as well as the Universities of Bern and Geneva have discovered that exoplanets called sub-Neptunes do indeed have differences in density. Until now, it was thought that these differences might possibly be due to different measurement methods.

An international team of astronomers led by the National Center of Competence in Research (NCCR) PlanetS and the Universities of Bern and Geneva has solved the mystery of a long-unexplained phenomenon. The researchers have published a study which, according to a press release, explains that there are indeed certain exoplanets, known as sub-Neptunes, which have different densities.

Most planets orbiting stars in our galaxy can be referred to as sub-Neptunes. In terms of size, the most common are between the radius of the Earth (about 6,400 kilometers) and that of Neptune (about 25,000 kilometers). In essence, they are larger than the Earth, but smaller than Neptune.

According to this study, the fact that differing densities were measured for sub-Neptunes has nothing to do with the two different measurement methods that are usually used. It was previously thought that this might be the cause of the issue. However, selection or observational bias can now be definitively ruled out.

According to Adrien Leleu, assistant professor at the Astronomy Department of the University of Geneva, the team asked themselves “whether there was an intrinsic connection between density and the resonant orbital configuration of a planetary system”. Then, using statistical tests, the researchers were able to determine that the density of sub-Neptunes in the resonant systems is lower than in the non-resonant systems - irrespective of which method was used to determine their mass. The main hypothesis for the cause is centered around the idea that different planetary formation processes exist. ce/mm

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