An astronomical waltz reveals a sextuplet of planets

By Nicholas Gerbis
Published: Monday, December 4, 2023 - 5:05am

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Scientists have discovered six planets moving in harmonic rhythm around HD110067, a bright star located 100 light years away.

According to the paper published in Nature, numerous satellites and telescopes contributed to the research, including the F. L. Whipple Observatory atop Mount Hopkins in southern Arizona.

Researchers found the worlds, which measure about two to three times the size of Earth, in data from NASA’s TESS craft (Transiting Exoplanet Survey Satellite), which spots exoplanets by observing the slight dimming they cause as they pass in front of their stars.

After taking a closer look with the European Space Agency’s CHEOPS vehicle (CHaracterising ExOPlanet Satellite), which estimates mass, density and composition, they calculated that all six planets move in resonance: In the time it takes the innermost world to revolve nine times around the star, the second revolves six times, the third four times, and so on.

ESA.
A rare family of six exoplanets has been unlocked with the help of ESA’s Cheops mission. The planets in this family are all smaller than Neptune and revolve around their star HD110067 in a very precise waltz.

Those ratios translate to resonant pairs of 3:2 (9/6) for the first and second planet as well as the second and third planet (6/4). The remaining resonant pairs are 3:2, 4:3 and 4:3.

Finding resonances that span such large systems is rare.

TRAPPIST-1 has seven resonant planets, but HD110067 is 50 times as bright. That renders its planets far easier to study, since scientists learn about planetary atmospheres by observing their star’s light filtering through them.

Our own solar system contains examples of resonances, too. Neptune and Pluto are in 3:2 resonance, and many moons of Saturn and Jupiter trace resonant orbits as well.

Thibaut Roger/NCCR PlanetS
Tracing a link between two neighbor planets at regular time interval along their orbits creates a pattern unique to each couple. The six planets of the HD110067 system create a mesmerizing geometric pattern due to their resonance chain.

Science