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The six planets of the HD 110067 system orbit in a regular pattern due to their gravitational influence on each other<\/p>\n
Thibaut Roger\/NCCR PlanetS (CC BY-NC-SA 4.0)<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
An ancient group of six exoplanets whose orbits have been unchanged for billions of years could tell us about how planetary systems like our own solar system formed.<\/p>\n
When planets orbit a star in a fixed, regular pattern, they are said to be resonant. They will continue like this until they are knocked off course by another large object passing nearby or smashing into them, setting them on a chaotic changing orbit. For instance, it is thought that Jupiter and Saturn swapped places early on in the solar system\u2019s formation as they passed close by.<\/p>\n
\u201cOnce there is a chaotic movement in a system, you will lose the information from initial conditions. You cannot trace back where the planets were in the past,\u201d says Rafael Luque at the University of Chicago. But without this chaotic movement, a resonant system will remain unchanged from its birth, he says.<\/p>\n
<\/p>\n In 2020, astronomers discovered a pair of resonant planets around the star HD 110067, about 100 light years away, using the Transiting Exoplanet Survey Satellite (TESS). But Luque and his colleagues noticed there were other signals in the data that didn\u2019t make sense. They followed up this observation a couple of years later with TESS and the space-based CHaracterising ExOPlanet Satellite (CHEOPS), and found a third planet, but the signals still weren\u2019t fully explained.<\/p>\n The team looked at simulations of the signal that different combinations of resonant planets would produce \u2014 some planets will go around the star three times in the time that it takes another planet to go around twice, for example. This revealed a system involving six planets, all orbiting in a flat plane, that almost perfectly fit the data.<\/p>\n \u201cIt is really an impressive feat how perfectly resonant the system is,\u201d says Luque. \u201cIf you take a mathematical solution, you could predict the periods [how long the planets take to orbit the star] exactly at the right time where we actually see them.\u201d<\/p>\n \n