An artist’s illustration of the six newly discovered planets circling their star in resonance. Credit: Roger Thibaut (NCCR PlanetS)
Researchers led by Rafael Luque discovered six planets in a rare gravitational resonance around a smaller, cooler star. This unique arrangement, stable since the system’s formation, was identified using data from NASA’s TESS and ESA’s CHEOPS, revealing insights into planetary evolution.
The Discovery
Six planets orbit their central star in a rhythmic beat, a rare case of an “in sync” gravitational lockstep that could offer deep insight into planet formation and evolution.
Key Facts
A star smaller and cooler than our Sun hosts a truly strange family of planets: six “sub-Neptunes” – possibly smaller versions of our own NeptuneNeptune is the farthest planet from the sun. In our solar system, it is the fourth-largest planet by size, and third densest. It is named after the Roman god of the sea.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Neptune – moving in a cyclic rhythm. This orbital waltz repeats itself so precisely it can be readily set to music.
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This animation shows six “sub-Neptune” exoplanets in rhythmic orbits around their star – with a musical tone as each planet passes a line drawn through the system. The line is where the planets cross in front of (“transit”) their star from Earth’s perspective. In these rhythms, known as “resonance,” the innermost planet makes three orbits for every two of the next planet out. Among the outermost planets, a pattern of four orbits for every three of the next planet out is repeated twice. Credit: Dr. Hugh Osborn, University of BernFounded in 1834, the University of Bern (German: Universität Bern, French: Université de Berne, Latin: Universitas Bernensis) is located in the Swiss capital of Bern. It offers a broad choice of courses and programs in eight faculties and some 150 institutes.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>University of Bern
Details
While multi-planet systems are common in our galaxy, those in a tight gravitational formation known as “resonance” are observed by astronomers far less often. In this case, the planet closest to the star makes three orbits for every two of the next planet out – called a 3/2 resonance – a pattern that is repeated among the four closest planets.
Among the outermost planets, a pattern of four orbits for every three of the next planet out (a 4/3 resonance) is repeated twice. And these resonant orbits are rock-solid: The planets likely have been performing this same rhythmic dance since the system formed billions of years ago. Such reliable stability means this system has not suffered the shocks and shakeups scientists might typically expect in the early days of planet formation – smash-ups and collisions, mergers and breakups as planets jockey for position. And that, in turn, could say something important about how this system formed. Its rigid stability was locked in early; the planets’ 3/2 and 4/3 resonances are almost exactly as they were at the time of formation. More precise measurements of these planets’ masses and orbits will be needed to further sharpen the picture of how the system formed.
Fun Facts
The discovery of this system is something of a detective story. The first hints of it came from NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA’s TESSLaunched on April 18, 2018, aboard a SpaceX Falcon 9 rocket, NASA’s Transiting Exoplanet Survey Satellite (TESS) is a space telescope mission to search nearby stars for undiscovered worlds with a goal of discovering thousands of exoplanets around nearby bright stars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>TESS (the Transiting Exoplanet Survey Satellite), which tracks the tiny eclipses – the “transits” – that planets make as they cross the faces of their stars. Combining the TESS measurements, made in separate observations two years apart, revealed an assortment of transits for the host star, called HD 110067. But it was difficult to distinguish how many planets they represented, or to pin down their orbits.
Eventually, astronomers singled out the two innermost planets, with orbital periods – “years” – of 9 days for the closest planet, 14 days for the next one out. A third planet, with a year about 20 days long, was identified with the help of data from CHEOPS, The European Space AgencyThe European Space Agency (ESA) is an intergovernmental organization dedicated to the exploration and study of space. ESA was established in 1975 and has 22 member states, with its headquarters located in Paris, France. ESA is responsible for the development and coordination of Europe's space activities, including the design, construction, and launch of spacecraft and satellites for scientific research and Earth observation. Some of ESA's flagship missions have included the Rosetta mission to study a comet, the Gaia mission to create a 3D map of the Milky Way, and the ExoMars mission to search for evidence of past or present life on Mars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>European Space Agency’s CHaracterising ExOPlanets Satellite.
Then the scientists noticed something extraordinary. The three planets’ orbits matched what would be expected if they were locked in a 3/2 resonance. The next steps were all about math and gravity. The science team, led by Rafael Luque of the University of ChicagoFounded in 1890, the University of Chicago (UChicago, U of C, or Chicago) is a private research university in Chicago, Illinois. Located on a 217-acre campus in Chicago's Hyde Park neighborhood, near Lake Michigan, the school holds top-ten positions in various national and international rankings. UChicago is also well known for its professional schools: Pritzker School of Medicine, Booth School of Business, Law School, School of Social Service Administration, Harris School of Public Policy Studies, Divinity School and the Graham School of Continuing Liberal and Professional Studies, and Pritzker School of Molecular Engineering.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>University of Chicago, worked through a well-known list of resonances that potentially could be found in such systems, trying to match them to the remaining transits that had been picked up by TESS.
The only resonance chain that matched up suggested a fourth planet in the system, with an orbit about 31 days long. Two more transits had been seen, but their orbits remained unaccounted for because they were only single observations (more than one transit observation is needed to pin down a planet’s orbit). The scientists again ran through the list of possible orbits if there were two additional, outer planets that fit the expected chain of resonances across the whole system. The best fit they found: a fifth planet with a 41-day orbit, and a sixth just shy of 55.
At this point, the science team almost hit a dead end. The slice of the TESS observations that had any chance of confirming the predicted orbits of the two outer planets had been set aside during processing. Excessive light scattered through the observation field by Earth and the Moon seemed to make them unusable. But not so fast. Scientist Joseph Twicken, of the SETI Institute and of the NASA Ames Research Center, took notice of the scattered light problem. He knew that scientist David Rapetti, also of Ames and of the Universities Space Research Association, happened to be working on a new computer code to recover transit data thought to be lost because of scattered light. At Twicken’s suggestion, Rapetti applied his new code to the TESS data. He found two transits for the outer planets – exactly where the science team led by Luque had predicted.
The Discoverers
An international team of researchers led by Rafael Luque, of the University of Chicago, published a paper online on the discovery, “A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067,” in the journal Nature on November 29.
Reference: “A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067” by R. Luque, H. P. Osborn, A. Leleu, E. Pallé, A. Bonfanti, O. Barragán, T. G. Wilson, C. Broeg, A. Collier Cameron, M. Lendl, P. F. L. Maxted, Y. Alibert, D. Gandolfi, J.-B. Delisle, M. J. Hooton, J. A. Egger, G. Nowak, M. Lafarga, D. Rapetti, J. D. Twicken, J. C. Morales, I. Carleo, J. Orell-Miquel, V. Adibekyan, R. Alonso, A. Alqasim, P. J. Amado, D. R. Anderson, G. Anglada-Escudé, T. Bandy, T. Bárczy, D. Barrado Navascues, S. C. C. Barros, W. Baumjohann, D. Bayliss, J. L. Bean, M. Beck, T. Beck, W. Benz, N. Billot, X. Bonfils, L. Borsato, A. W. Boyle, A. Brandeker, E. M. Bryant, J. Cabrera, S. Carrazco-Gaxiola, D. Charbonneau, S. Charnoz, D. R. Ciardi, W. D. Cochran, K. A. Collins, I. J. M. Crossfield, Sz. Csizmadia, P. E. Cubillos, F. Dai, M. B. Davies, H. J. Deeg, M. Deleuil, A. Deline, L. Delrez, O. D. S. Demangeon, B.-O. Demory, D. Ehrenreich, A. Erikson, E. Esparza-Borges, B. Falk, A. Fortier, L. Fossati, M. Fridlund, A. Fukui, J. Garcia-Mejia, S. Gill, M. Gillon, E. Goffo, Y. Gómez Maqueo Chew, M. Güdel, E. W. Guenther, M. N. Günther, A. P. Hatzes, Ch. Helling, K. M. Hesse, S. B. Howell, S. Hoyer, K. Ikuta, K. G. Isaak, J. M. Jenkins, T. Kagetani, L. L. Kiss, T. Kodama, J. Korth, K. W. F. Lam, J. Laskar, D. W. Latham, A. Lecavelier des Etangs, J. P. D. Leon, J. H. Livingston, D. Magrin, R. A. Matson, E. C. Matthews, C. Mordasini, M. Mori, M. Moyano, M. Munari, F. Murgas, N. Narita, V. Nascimbeni, G. Olofsson, H. L. M. Osborne, R. Ottensamer, I. Pagano, H. Parviainen, G. Peter, G. Piotto, D. Pollacco, D. Queloz, S. N. Quinn, A. Quirrenbach, R. Ragazzoni, N. Rando, F. Ratti, H. Rauer, S. Redfield, I. Ribas, G. R. Ricker, A. Rudat, L. Sabin, S. Salmon, N. C. Santos, G. Scandariato, N. Schanche, J. E. Schlieder, S. Seager, D. Ségransan, A. Shporer, A. E. Simon, A. M. S. Smith, S. G. Sousa, M. Stalport, Gy. M. Szabó, N. Thomas, A. Tuson, S. Udry, A. M. Vanderburg, V. Van Eylen, V. Van Grootel, J. Venturini, I. Walter, N. A. Walton, N. Watanabe, J. N. Winn and T. Zingales, 29 November 2023, Nature.
DOI: 10.1038/s41586-023-06692-3
Source: SciTechDaily
