Space, a rare system of 6 billion-year-old exoplanets discovered by the Cheops telescope

They are inside a star system that has remained almost similar to the moment of its formation, even Italy is in pole position in the European Space Agency mission

A rare star system discovered within which they ‘live’ six exoplanets extrasolar planets – and the rarity of this system is that it has remained more or less similar to the time of its birth, about a thousand million years ago. It was discovered by Cheops space telescope of ESA el‘European Space Agency, in making the announcement, explained that it is a discovery “particularly precious because the orbital configuration of the planets shows that the system has remained substantially unchanged since its formation, which occurred more than a billion years ago”. Launched on 18 December 2019, Cheops (CHaracterising ExOPlanets Satellite) is a space telescope for the study of extrasolar planets, via the transit method.

ESA’s ExOPlanet Satellite (CHEOPS) telescope has provided crucial data to understand the mysterious system of exoplanets that had puzzled researchers for years. The six planets orbit their star, called HD110067, which is about 100 light-years away in the northern constellation Coma Berenices. ESA recalls that already in 2020, NASA’s Tess-Transiting Exoplanet Survey Satellite had detected dips in the star’s brightness which indicated that planets were passing in front of its surface.

And Italy also has a leading role in the Cheops mission. The ESA probe in fact scans space also thanks to sophisticated ‘eyes’ designed and built by the Italian giant Leonardo. The Cheops space telescope, commissioned by the Italian Space Agency, was in fact designed and built in the Leonardo in Campi Bisenzio, near Florence, where engineers, physicists and specialized technicians created the instrument according to the requirements defined by researchers from the Inaf-National Institute of Astrophysics of Padua and Catania, in collaboration with the University of Bern.

In particular, Leonardo, together with the contribution of small and medium-sized companies, oversaw the creation of the telescope’s optical system, based on aspheric mirrors, and the collimation optics on the focal plane (mirror and lenses). The Italian team also includes researchers from the University of Padua and the ASI Space Science Data Center and contributed to defining the requirements, verifying the instrumental performances and preparing the data analysis.

In detailing the new discovery, the European Space Agency reported that a preliminary analysis of the system had revealed two possible planets, one with an orbital period – the time it takes to complete one orbit around the star – of 5,642 days , and the other with a period that has not yet been possible to determine. But two years later, the Tess satellite observed the same star again and analysis of the combined data ruled out the original interpretation but presented two different possible planets. ESA scientists explained that even though these detections were much more certain than the originals, there was a lot in the TESS data that still didn’t make sense. It was then that Rafael Luque of the University of Chicago and his colleagues became interested in this ‘slice of the universe’.

“We decided to use Cheops and went looking for signals among all the potential periods that those planets could have,” reported astrophysicist and astronomer Rafael Luque. The efforts bore fruit because they confirmed the presence of a third planet in the system and so scientists realized that they had found the key to ‘unlock’ the entire system because it was now clear that the three planets were in resonance orbital. Once they had a clearer picture, scientists realized that the outermost planet takes 20,519 days to orbit, which is extremely close to 1.5 times the orbital period of the next planet at 13,673 days. This, in turn, is almost exactly 1.5 times the orbital period of the inner planet, at 9,114 days.

Predicting other orbital resonances and matching them with the remaining hitherto unexplained data allowed the team to discover the other three planets in the system. “Cheops gave us the configuration that allowed us to predict all the other periods. Without Cheops detection it would have been impossible,” Rafael noted. The European Space Agency explained that orbitally resonant systems are extremely important to find because they tell astronomers about the formation and subsequent evolution of the planetary system. Planets around stars tend to form in resonance but can be easily perturbed.

For example, ESA continued, a very massive planet, a close encounter with a passing star or a gigantic impact event can upset the delicate balance. As a result, many of the multi-planet systems known to astronomers are not in resonance but appear close enough to have been in resonance once. However, multi-planet systems that preserve their resonance are rare. “We believe that only about 1% of all systems remain in resonance,” Rafael added. This is why, according to scientists, HD110067 is special and pushes for further studies. “It shows us the original configuration of a planetary system that survived intact,” said the University of Chicago astrophysicist.

Maximilian Günther, ESA project scientist for Cheops, added that “as our scientific team says, Cheops is making exceptional discoveries seem ordinary. Of only three known six-planet resonant systems this is the second found by Cheops and in just three years of activity”. HD110067 is the brightest known system with four or more planets. Since these planets are all smaller in size than Neptune and likely have large atmospheres, this makes them ideal candidates for studying the composition of their atmospheres using the NASA/ESA/CSA James Webb Space Telescope and the future ESA Ariel and Plato telescopes.