A team of scientists realized quite the discovery recently. Their work comprises seven years of continuous monitoring. A system of six exoplanets is orbiting the star dubbed HD 158259. Until now, scientists found hundreds of stars with lots of planets orbiting them shattered throughout the galaxy.
Why is this time different? Star HD 158259 is almost the Sun’s mass, but a little bit larger. Five mini-Neptunes and a super-Earth orbit the star in what it appears to be, the perfect orbital resonance.
Orbital resonance happens when the orbits of two space objects close to their host are linked, as the two orbiting cosmic features apply gravitational influence on each other. Orbital resonances have also been found in exoplanets.
The recent discovery is different because each planet orbiting HD 158259 is in a nearly 3:2 resonance with the next planet, defined as a period ratio of 1:5. Such a thing means that for every three orbits each planet performs, the next one makes two.
The exoplanets orbit in perfect resonance
The discovery was possible thanks to a team of scientists led by Nathan Hara, an astronomer from the University of Geneva. They utilized the SOPHIE spectrograph and the TESS exoplanet-hunting space telescope to precisely measure the orbits of each planet.
The results showed that all of them are very tight. Beginning closest to HD 158259 – the super-Earth, unveiled by TESS to be near twice the mass of Earth – the orbits are 17.4, 12, 7.9, 5.2, 3.4, 2.17 days.
The orbits make period ratios of 1.44, 1.51, 1.53, 1.51, and 1.57 between each pair of exoplanets. Even if all these results don’t represent a perfect resonance, it’s close enough to define star HD 158259 as a fantastic system. The team thinks that the planets orbiting the star weren’t born where they’re now.
“Such systems are believed to form far from the star before migrating towards it – in this scenario, the resonances play a crucial part,” detailed Stephane Udry, an astronomer from the University of Geneva.