Astronomers have mapped a rare planetary system using the Cheops space telescope

According to a statement from the HUN–REN Astronomy and Earth Science Research Center (CSFK), the discovery, to which the work of Hungarian researchers also contributed, is particularly interesting because the orbits of the planets indicate that the system has spent more than a billion years since its formation in a fundamentally unchanged state.

An article presenting the results of the researchers was published on Wednesday in the scientific journal Nature.

The star with catalog number HD110067 is almost 100 light-years away from Earth, in the northern hemisphere, in the constellation Coma Berenices. Its mass and radius are about 80 percent of the Sun’s.

In 2020, NASA’s TESS (Transiting Exoplanet Survey Satellite) detected dips in the star’s brightness that suggested planets were passing in front of the star’s disk. The preliminary analysis revealed two possible planets, they wrote.

Two years later, TESS detected the star again. The combined analysis of the previous and new data ruled out the original interpretation, and instead made the existence of two other planets different from those in the first explanation likely. Although these detections were much less uncertain than the first ones, much of the TESS data was still unclear. It was then that Rafael Luque (University of Chicago) and his colleagues became interested in the phenomenon.

As a result of their efforts, they managed to confirm the presence of a third planet in the system, while also finding the key to the interpretation of the system, since it was clear that the three planets orbit in the system on so-called resonant orbits.

Predicting additional orbital resonances and comparing them with the remaining unexplained data allowed the team to discover the other three planets in the system.

The identification of resonant planetary systems is extremely important, as they reveal important information to researchers about the formation of the systems and the development of the immediately following period. “It seems that the planets mostly form in resonant orbits around the stars, but they can very easily leave them under the influence of even the smallest disturbances (perturbations). For example, a very massive planet, another star passing nearby, or even a massive impact event could easily end the delicate balance,” the researchers explained.

According to the report, astronomers know of many multi-planet systems in which resonance no longer exists, but whose orbital periods are such that this may have been the case at some point in the past. However, planetary systems that retain the resonance state for a long time are rare.

“We believe that only about one percent of all systems remain in a resonant state,” explains Rafael Luque. That is why HD110067, which still shows its ancient state, is special and worthy of further investigation.

According to the report, only three resonant planetary systems with six planets are known so far, and astronomers can thank Cheops for two of them.

“The new discovery of Cheops clearly proves that the concept of an ultra-precise space photometer that can be directed almost anywhere in the sky, the operating principle formulated a good 10 years ago, works perfectly. We could never have known the true nature of the exotic system found by the American TESS space telescope without Cheops’ flexible and target-adaptive data collection,” emphasized László Kiss, Hungarian member of the Cheops consortium’s scientific steering board, in the announcement.

HD110067 is the brightest star with at least four planets orbiting it. Because they are all smaller than Neptune and likely have extensive atmospheres, they are ideal targets for the NASA/ESA/CSA James Webb Space Telescope and ESA’s future Ariel and Plato space telescopes, which will also study the composition of the planets’ atmospheres.

According to the announcement, the discovery involved Tamás Bárczy (ADMATIS Kft., Miskolc), Csizmadia Szilárd (Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt, Berlin), László Kiss (HUN–REN Astronomy and Earth Science Research Center, Budapest), Simon Attila ( Abteilung für Weltraumforschung und Planetologie, Physikalisches Institut, Universität Bern, Bern) and Gyula M. Szabó (ELTE Gothard Astrophysical Observatory, Szombathely) also contributed.