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A team of researchers led by University of Chicago astronomer Rafael Luque analyzed data acquired by both NASA\u2019s Transiting Exoplanet Survey Satellite (TESS) and ESA\u2019s CHaracterising ExOPlanet Satellite (Cheops) and found a unique planetary system. Orbiting a star cataloged as HD110067, this system contains six sub-Neptune planets. Incredibly, all six planets are orbiting in direct resonance with each other. The results of the work were published on November 29 in Nature<\/em>.<\/span><\/p>\n <\/p>\n In 2020, transit data collected by TESS, which tracks the change in the star\u2019s brightness, revealed at least two planets. Their orbits were about nine days for the closer and fourteen days for the farther world. Additionally, the transits provided hints of several more planets. Then follow-up data from Cheops identified a third planet orbiting in twenty days.\u00a0<\/span><\/p>\n From these orbital periods, Luque realized that these three planets orbited in a 3\/2 resonance with each other. Planet b, the innermost, orbits three times in the same amount of time that planet c, the next one out, orbits twice. Planet c orbits three times while planet d orbits twice. Next came a lot of math.<\/span><\/p>\n Working through the calculations to find potential resonances, the team matched one set of transits to a planet orbiting in 31 days. Again, the orbit was a 3\/2 resonance, with planet d orbiting three times to planet e\u2019s two times. However, there were possibly two more unmatched transits in the data. TESS had only observed each one a single time, making confirmation difficult. One planet orbited in 41 days; the other in 55.<\/span><\/p>\n Adding to the difficulty, the TESS data that could have confirmed the outer two planets contained excessive light from the Earth and Moon. Enter scientists Joseph Twicken (SETI Institute, NASA Ames Research Center) and David Rapetti (NASA Ames and USRA),<\/span> who were working on code to recover lost data due to scattered light. Rapetti applied the code to the TESS data and found the two transits as predicted.<\/span><\/p>\n While multi-planet systems turned out to be common, this system\u2019s resonant orbits are special. Luque notes, \u201cWe think only about one percent of all systems stay in resonance, and even fewer show a chain of planets in such configuration.\u201d Staying in resonance with six planets means this system may answer questions about planetary formation. Luque explains, \u201cIt shows us the pristine configuration of a planetary system that has survived untouched.\u201d<\/span><\/p>\n \n