In a significant astronomical breakthrough, researchers have uncovered a small, cold exoplanet and its massive outer companion, shedding light on the intricate processes behind the formation of planets like Earth.
This rare discovery, led by Neda Heidari from the Institut d’astrophysique de Paris, marks a crucial step in understanding the dynamics of planetary evolution. The newfound planetary system orbits the star HD88986, with the smaller exoplanet, named HD88986b, falling within the sub-Neptune category. Positioned between the size and mass of Earth and Neptune, HD88986b boasts a lengthy orbital period of 146 days, a notable feature among known exoplanets smaller than Neptune or Uranus. The star system also hosts an outer companion, exceeding 100 times the mass of Jupiter.
Detection of HD88986b was made possible by the high-precision spectrograph SOPHIE at the Haute-Provence Observatory in France. SOPHIE utilizes the radial-velocity method, measuring the subtle motion variations induced by orbiting planets on their host stars. The observations allowed scientists to estimate HD88986b’s mass to be approximately 17 times that of Earth.
Complementary data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s Characterising ExOPlanet Satellite (CHEOPS) indicated that HD88986b likely undergoes “transits,” partially obscuring its host star when viewed from Earth. This phenomenon enabled scientists to directly estimate the planet’s diameter, revealing it to be twice that of Earth.
The significance of HD88986b lies not only in its size and orbital characteristics but also in its atmosphere temperature of a mere 190 degrees Celsius, providing a unique opportunity to study “cold” atmospheres, a rarity in exoplanet observations.
With a wide orbit and weak mass loss due to ultraviolet radiation, HD88986b offers insights into its original chemical composition, setting the stage for exploring diverse scenarios for the planetary system’s formation and evolution.
Thomas Wilson, a senior research fellow at the University of Warwick, highlighted HD88986b as a scaled-down Neptune, orbiting between Mercury and Venus. This discovery positions HD88986b as one of the most thoroughly studied small, cold exoplanets, paving the way for atmospheric studies and drawing parallels to Earth.
In addition to HD88986b, a second outer companion was unveiled around the central star. This massive exoplanet, with an orbit spanning several tens of years, presents another layer of intrigue that awaits further observations to unravel its nature and properties.
The findings, spanning over 25 years of observations and involving data from various satellites and telescopes, contribute to our expanding understanding of planetary systems, emphasizing the vital role of rare discoveries in unraveling the mysteries of the cosmos.
