Imagine a star system just like our own Sun, but with a hidden treasure trove of planets waiting to be discovered. That’s exactly what astronomers have found around HD 85426, a star so similar to our Sun it’s like looking at a cosmic mirror. Using the powerful eyes of HARPS-N, TESS, and CHEOPS, scientists have unveiled a fascinating planetary system, and it’s not just one world, but three! But here’s where it gets really exciting: one of these planets is a sub-Neptune, a type of world we’re still trying to understand, and it’s orbiting in the habitable zone, where conditions could be just right for life as we know it. And this is the part most people miss: there are two more planets lurking in the shadows, not visible to our telescopes, but their gravitational pull gives them away. This discovery, led by F. Lienhard and a team of international astronomers, is a game-changer for astrobiology, offering a unique glimpse into a system that could hold clues to the origins of life in our universe.
In their 27-page study, soon to be published in MNRAS, the team meticulously characterizes the HD 85426 system. This star, a near-twin to our Sun with a mass of 0.99 solar masses and an age of 7.4 billion years, hosts a transiting sub-Neptune named HD 85426 b. This planet, with an orbital period of 16.71 days, has a blackbody equilibrium temperature of around 824 K, making it a prime candidate for further atmospheric studies. By combining data from HARPS-N’s radial velocity measurements and photometric observations from TESS and CHEOPS, and employing advanced stellar activity mitigation techniques, the researchers estimate the planet’s mass to be between 6.0 and 8.5 Earth masses, depending on the method used. But here’s the controversial part: how do we accurately account for stellar activity in our measurements? Could our current techniques be missing something fundamental?
The team didn’t stop at HD 85426 b. They also detected two additional non-transiting planets with minimum masses around 10 Earth masses and orbital periods of 35.7 and 89 days. Interestingly, they ruled out the initial hypothesis that the 35.7-day signal was caused by stellar activity, a common challenge in exoplanet detection. Furthermore, they determined HD 85426 b’s radius to be approximately 2.78 Earth radii and calculated a transmission spectroscopy metric between 82 and 115, making it an ideal target for future atmospheric characterization missions. This metric suggests that the planet’s atmosphere could be studied in detail, potentially revealing its composition and structure.
This discovery raises intriguing questions about the formation and evolution of planetary systems around Sun-like stars. Could systems like HD 85426 be common in our galaxy? And what does this mean for the likelihood of finding Earth-like planets in habitable zones? As we continue to explore the cosmos, findings like these not only expand our understanding of planetary systems but also fuel our imagination about the possibilities of life beyond Earth. What do you think? Are we getting closer to finding another Earth, or is the universe full of surprises we can’t yet imagine? Share your thoughts in the comments below!