The American TESS and European CUPS telescopes observed a system consisting of six planets outside the solar system rotating at a very regular pace around their star, which constitutes an important discovery for understanding the formation of the solar system.
The six planets revolve around HD 110067, a bright star located about 100 light-years from our solar system in the constellation Coma, and can be seen from the Earth’s northern hemisphere.
Adrian Lelio, from the University of Geneva, one of the main authors of the study published in the journal Nature, points out that what was discovered is a very compact system that fits within the orbit of Mercury, the planet closest to the sun.
All of these planets are hot, and their diameter ranges between the size of the diameter of Earth and the diameter of Neptune. Its components are similar to those of Neptune. The astrophysicist says that it is a “rocky body covered with a thick envelope of gas.”
None of these “mini-Neptunes” are located in a habitable zone, that is, at a good distance that makes the presence of liquid water possible on them, because this component is essential for the existence of life on planets.
The six observed planets have notable features: their orbital periods, that is, the time they take to orbit their star, are highly synchronized, something that has not been observed in a group of more than 5,000 planets outside the solar system since the discovery of the first in 1995.
The telescope initially detected two planets using the transit method, which measures changes in light resulting from a planet passing in front of its host star. However, strange transit signals aroused the curiosity of astronomers who suspected the existence of other planets that are more distant and therefore have a longer rotation period, which TESS was unable to discover. Because this telescope is designed to observe the sky over periods of up to a few weeks, not to observe longer orbits.
Then astronomers used the European Space Agency’s Cheops telescope, which is “capable of observing a star for a long time,” as Hugh Osborne, one of the study’s authors and a researcher from the University of Bern, explains. Gradually, Cheops was able to observe four other planets. “The mystery will finally be solved in 2023,” Osborne says.
The rotation mechanism of the planets is very regular, as when the first planet completes three revolutions around the star, the second planet performs two revolutions, and when the second completes three revolutions, the third completes two revolutions, and so on. In the end, the last planet makes one revolution and the first makes six, evidence that all the planets are connected through a “chain of resonance,” Lelio says.
