Astronomers stunned by six-planet system frozen in time
https://www.science.org/content/article/astronomers-stunned-six-planet-system-frozen-time
By DANIEL CLERY, Science.
Excerpt: Astronomers have discovered a highly unusual planetary system ...six planets, all bigger than Earth but smaller than Neptune, a variety that is absent in our Solar System but common across the Milky Way. Moreover, all of the planets orbit in rhythmic harmony, which suggests the system has remained undisturbed since its formation billions of years ago. The brightness of the star, its relative proximity to Earth, and its six orbiting oddities could make the system a perfect laboratory for studying the formation of these planets, known as sub-Neptunes. ...the study, published today in Nature. The planets’ orbits are all tighter than Mercury’s. ...a mysterious [size] gap persists: Planets between 1.5 and two Earth diameters seem almost entirely absent and astronomers are eager to know why. ...The new system’s discovery involved two space telescopes, multiple ground-based ones, and more than 3 years of detective work by dozens of astronomers. The hunt began in 2020 ...from NASA’s Transiting Exoplanet Survey Satellite (TESS), which looks for dips in a star’s brightness caused by planets passing in front. He noticed intriguing but inconclusive dips associated with HD 110067, a Sun-like star just 100 light-years from Earth. ...Subsequent observations by the European Space Agency’s Characterising Exoplanet Satellite (CHEOPS) identified a third planet, with an orbital period of 20.5 days. ...The orbits of the three known planets showed a 3/2 resonance between each neighboring pair: For every three times the inner planet orbits, the outer neighbor orbits twice. On a hunch that others could also be in resonance, Luque’s team looked for additional hypothetical planets with resonances of 2/1, 3/2, 4/3, and so on. A fourth planet, in a 3/2 resonance and with an orbital period of 30.8 days, perfectly matched two of the transits. ...the researchers were able to show how the two remaining transits would fit well with planets orbiting every 41.1 days and 54.7 days. Each of those planets is in a 4/3 resonance with its inner neighbor....