In a groundbreaking initiative to unravel the mysteries of planetary formation, a team of scientists led by the University of Geneva’s Department of Astronomy has launched the ATREIDES program. This ambitious project focuses on exo-Neptunes, a class of exoplanets that are approximately 20 times more massive than Earth and reside outside our solar system. The program aims to deepen our understanding of the physical mechanisms that govern the formation and evolution of planetary systems.
Exo-Neptunes have intrigued astronomers for years, especially due to their peculiar distribution across the cosmos. While these planets are notably absent in regions close to stars, recent studies indicate their prevalence in more temperate zones, known as the “savanna.” Between this savanna and the barren “desert” regions lies the “Neptunian ridge,” where exo-Neptunes appear even more frequently. This complex landscape offers a unique opportunity to study the processes involved in planetary evolution.
The ATREIDES Program: A Collaborative Effort
The ATREIDES program is spearheaded by Vincent Bourrier, a senior lecturer and researcher at the University of Geneva. The initiative is based on a large-scale observation program conducted on the European Southern Observatory’s Very Large Telescopes (VLTs), utilizing ESPRESSO, the world’s most accurate spectrograph.
“The complexity of the exo-Neptunian landscape provides a unique window onto the processes involved in the formation and evolution of planetary systems,” explains Vincent Bourrier.
The program’s primary focus is to identify the processes responsible for the formation of the Neptunian desert, savanna, and ridge. By observing and analyzing data from a large number of Neptunes, scientists hope to derive more general insights into planetary formation. This systematic approach is expected to enable meaningful comparisons between different planetary systems.
International Collaboration and Methodology
Designed as an open, international community initiative, the ATREIDES collaboration invites astronomers worldwide to join the scientific effort. The University of Warwick, for instance, is using the NGTS telescopes to observe the transits of these Neptunes, optimizing the use of ESPRESSO/VLT for more accurate measurements.
“We are using the NGTS telescopes to observe the transits of these Neptunes and thus optimize our use of ESPRESSO/VLT. This allows us to obtain much more accurate measurements and identify processes, such as stellar flares, that could affect the ESPRESSO data,” says Daniel Bayliss, associate professor at the University of Warwick.
Case Study: The TOI-421 System
The first system observed under the ATREIDES program is TOI-421, which comprises two planets: TOI-421 c, a hot Neptune located in the savanna, and TOI-421 b, a smaller planet closer to the star. This system’s chaotic history provides valuable insights into the migration patterns of exo-Neptunes.
One hypothesis suggests that the Neptunian landscape is shaped by the migration of planets from their birthplaces to their current orbits. Some planets migrate slowly and early through the gas disk, resulting in aligned orbits, while others experience “high-eccentricity migration,” leading to misaligned orbits. By measuring the alignment of TOI-421, scientists discovered that its planets are highly misaligned, indicating a turbulent evolutionary history.
Implications for Future Research
The analysis of TOI-421 is just the beginning. The findings not only provide valuable data but also help refine the analytical tools developed within the ATREIDES collaboration. However, a comprehensive understanding of planetary formation requires observing and analyzing numerous exo-Neptunes with the same rigor.
“A thorough understanding of the mechanisms that shape the Neptunian desert, savanna, and ridge will provide a better understanding of planetary formation as a whole… but it’s a safe bet that the Universe has other surprises in store for us, which will force us to develop new theories,” concludes Vincent Bourrier.
The ATREIDES program represents a significant step forward in the field of astronomy, offering a promising path toward unraveling the complexities of planetary systems. As the research progresses, it is expected to yield new insights and potentially redefine our understanding of the universe.