Astronomers have discovered an exceptionally rare phenomenon in a nearby star system — six planets that orbit their central star in sync with a rhythm. The planets move around in a pattern so precise that it can be set to music. The six planets orbit a star called HD110067, which is about 100 light-years away from the Earth in the northern constellation of Coma Berenices. NASA’s Transiting Exoplanet Survey Satellite (TESS) in 2020 detected the star’s brightness dipping, indicating that planets were passing in front of it. A team of researchers combined data from TESS and the European Space Agency’s (ESA) Cheops (CHaracterising ExOPlanet Satellite) and ended up discovering a planetary configuration that had never been seen before. Multiplanet systems may be common in our galaxy, but ones in a tight gravitational formation known as “resonance” are rarely observed. In this particular case, the planet closest to the star makes three orbits for every two of the next planet. This is called a 3/2 resonance and is repeated among the four closest planets. Among the two outermost ones, a 4/3 resonance pattern was identified, meaning that one takes four orbits for every three of the outermost one. Such “orbitally resonant” systems are quite important because they tell astronomers about the formation and evolution of planetary systems. Typically, planets around stars tend to form in resonance, but that can easily be disturbed. For example, a very massive planet or a close encounter with a passing star or even a giant impact can all disrupt a planetary system that was once in balance. Due to this, many multiplanet systems are not in resonance, but they are close enough that they look like they may once have been in resonance.
