A rare family of six sub-Neptune planets, orbiting a star called HD110067, create a geometric pattern due to their resonance. Astronomers used two different exoplanet-detecting satellites to solve a cosmic mystery and reveal this unprecedented system, located approximately 100 light-years from Earth. The star is situated in the Coma Berenices constellation in the Northern sky, and the presence of the six exoplanets orbiting around it is a crucial discovery for understanding the formation of planets. These planets are larger than Earth but smaller than Neptune, falling into a little-understood category known as sub-Neptunes, which are common around sunlike stars in the Milky Way. Labeled as b through g in relation to their distance from the star, the planets follow a celestial dance known as orbital resonance, creating discernible patterns as they exert gravitational forces on one another. This discovery demonstrates that these planetary formations are essentially unchanged since being formed over a billion years ago. The revelation could contribute to scientists’ understanding of planet evolution and the origin of sub-Neptunes in the galaxy. Baylor Fox-Kemper, a professor of Earth, environmental and planetary sciences at Brown University, said in the journal Nature, “The work is significant as it is among the first to characterize the resonant chain of six … exoplanets in our galaxy.”

One of the key elements of the discovery was the use of NASA’s Transiting Exoplanet Survey Satellite (TESS) to observe the star and detect dips in its brightness. This suggested the potential presence of planets as they crossed between the star and the satellite in their orbital paths. While the TESS data revealed the orbital period of two planets, these findings were not consistent with evidence observed later, leading the research team to use researchers from the European Space Agency’s CHaracterizing ExOPlanet Satellite (Cheops) to study the star. The data collected from Cheops helped to solve the mystery and confirm the presence of the six planets, revealing their rhythmic resonance as they orbited the star. This new discovery helps to shed light on the formation and evolution of planetary systems and the unique nature of the planets composing the system. Furthermore, the existence of this system presents an opportunity to study how sub-Neptunes form, which has been a point of contention among astronomers. Each of these planets orbits their star at a faster pace than Mercury orbits the sun, suggesting that they maintain higher average temperatures due to their proximity to their star. There is still much that remains unknown, but this rare system will help to broaden our knowledge of exoplanetary systems and their unique characteristics.

The discovery adds to growing knowledge of orbital resonances in exoplanetary systems. Only three systems with six planets in resonance are currently known. The first such system was discovered in 2020 using TESS and Cheops, and this discovery reinforces the idea that such systems are an essential puzzle piece in understanding the development of planetary systems. The study’s findings are also a testament to the vital role satellites like TESS and Cheops play in uncovering these cosmic mysteries, of which little is still understood about our universe.