NASA has discovered six exoplanets orbiting a nearby bright star HD110067 in the constellation Coma. These planets have a radius between Earth and Neptune. The researchers calculated details of their orbits and estimated their masses and densities, providing clues about the system's formation and the composition of the planet's atmosphere. Relevant research was published in "Nature" on November 30.
Planets with radii between Earth and Neptune (so-called "sub-Neptunes") have been found in close orbits for more than half of all Sun-like stars, but the details of their composition, formation, and evolution are poorly understood. HD110067 is a bright star in the constellation Coma, visible from Earth's northern hemisphere.
NASA's "Transiting Exoplanet Survey Satellite" (TESS) observed HD110067 in 2020 and 2022 and found that the star's brightness dropped several times. Together with more observations from the "Exoplanet Characteristics Survey Satellite" (CHEOPS), Rafael Luque of the University of Chicago and his collaborators reported that these signs can be explained as six planets passing in front of the star.
By studying the three deepest planets, the researchers calculated the orbits of all six planets, from about 9 days at the deepest to about 54 days at the outermost. They calculated the masses of the planets and estimated their densities, speculating that large, hydrogen-rich atmospheres could explain their low densities. All six planets are in resonant orbits, which means the planets exert regular forces on each other as they move. This feature indicates that this system has been almost unchanged since its creation, which has been at least 4 billion years.
Researchers pointed out that HD110067 is the brightest star discovered so far with more than four transiting exoplanets. There may be more planets inside and outside the habitable zone, but they have not been observed so far. They concluded that the HD110067 system provides an opportunity to learn more about sub-Neptunes and how the system might have formed in that dynamic.
Related paper information: https://doi.org/10.1038/s41586-023-06692-3