Rare Discovery by Scientists: Solar System Found to Have Three Super-Earths
Astronomers have discovered a rare solar system containing three Super-Earths and two Super-Mercuries, a type of planet that is extremely distinct and scarce. These Super-Mercuries are so rare that only eight have been found to date. The star system HD 23472 was examined in a study published in Astronomy & Astrophysics, which explored the relationship between the composition of small planets, their position, temperature, and the attributes of the star. The study aimed to characterize the composition of small planets and examine the transition from having an atmosphere to not having one.
The ESPRESSO spectrograph was used to identify the two ‘super-Mercury’ worlds in this planetary system. According to project leader Susana Barros, a researcher at the Institute of Astrophysics e Ciências do Espaço (IA), the goal of observing this planetary system was to learn more about small planet composition and the atmospheric transition.
The researcher leading the project, Susana Barros, shared that the evaporation of the atmosphere in the planetary system could be linked to the radiation from the star. The surprising discovery was that the system is made up of three super-Earths with a significant atmosphere and two Super-Mercuries, which are the closest planets to the star.
The star system HD 23472 comprises five exoplanets, with three having masses less than that of Earth. Using the radial velocity method, the five planets were detected as among the lightest exoplanets ever found. The high precision of the discovery was possible due to ESPRESSO, a spectrograph located at the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile.
Super-Earths and super-Mercuries are analogous to Earth and Mercury in terms of composition, but with higher mass. The key difference between them is that super-Mercuries have a higher iron content, making them extremely rare.
The recent discovery of only eight known super-Mercuries, including the two found in the HD 23472 planetary system, raises the question of why Mercury has a larger and more massive core than other planets in our Solar System, despite being one of the densest planets. Some theories suggest that Mercury’s mantle may have been lost due to a massive impact, or its high temperatures could have melted some of its mantle. To gain a better understanding of such objects, astronomers need to locate other dense, Mercury-like planets orbiting other stars.
The discovery of two super-Mercuries in the same planetary system, instead of just one, provides valuable information to scientists. “We identified a system with two super-Mercuries for the first time using the ESPRESSO spectrograph. This helps us understand how these planets developed,” said Alejandro Suárez, a co-author of the study and researcher at the IAC.
Co-author and IAC researcher Jonay González stated that the notion of two giant impacts in the same system creating two super-Mercuries is highly implausible, given that even a massive impact forming a single super-Mercury is already unlikely. Further analysis of the composition of these planets is necessary to understand their evolution. With the first-generation high-resolution spectrograph ANDES and the Extremely Large Telescope (ELT), scientists will have the opportunity to study the surface composition and hypothetical atmosphere of these planets for the first time.
The presence of an atmosphere on a planet can provide insight into the origin and evolution of planetary systems and determine whether the planet is habitable. The team hopes to continue investigating longer-period planets with more suitable temperatures to learn more about the formation and evolution of planetary systems and to discover another Earth-like planet.
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