Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake. How do Planetary Systems Form?

The detection and characterization of protoplanets in protoplanetary disks around young stars is emerging as a transformative field that will redefine our understanding of how planetary systems form. While current facilities have revealed the diversity of mature exoplanets and the complex structures of disks, we still lack the crucial observational link between them: a statistically meaningful census of planets caught in the act of formation. This white paper argues that such a breakthrough requires access to the nearest and most informative star-forming regions, roughly half of which are poorly accessible or entirely unreachable from Cerro Armazones. Although the ELT alone will strongly impact our knowledge of planet formation, its location prevents Europe from fully exploiting the necessary parameter space. A 30-40 m telescope in the northern hemisphere is therefore essential for obtaining diffraction-limited imaging of protoplanets and disks across the entire sky, enabling robust demographics, exploiting synergies with ngVLA, Gaia, and other facilities covering the north, and ensuring that Europe remains at the forefront of the planet-formation revolution in the coming decades.

💡 Research Summary

The scientific community stands at a pivotal moment in the study of planetary evolution. While we have achieved remarkable success in identifying diverse mature exoplanets and mapping the intricate structures of protoplanetary disks, a critical observational gap remains: the “missing link” of planetary formation. We lack a statistically significant census of planets caught in the actual process of formation within their natal disks. This white paper argues that bridging this gap requires a strategic expansion of our observational capabilities, specifically through the construction of a 30-40 meter class telescope in the Northern Hemisphere.

The primary technical challenge in studying planet formation is the extreme difficulty of resolving small, faint protoplanets embedded within the bright, complex environments of protoplanetary disks. To achieve the necessary diffraction-limited imaging to separate a protoplanet from its host star, a massive aperture is non-negotiable. While the upcoming Extremely Large Telescope (ELT) in Chile represents a monumental leap in capability, its southern latitude imposes a significant geographical bias. A substantial portion of the most informative star-forming regions and molecular clouds—essential for studying the early stages of planet formation—are located in the Northern Hemisphere and are either poorly accessible or entirely invisible from the ELT’s location in Cerro Armazones.

The paper posits that a Northern Hemisphere 30-40m telescope is essential to achieve a truly “all-sky” perspective. Such a facility would enable astronomers to conduct a comprehensive demographic study of planet formation, moving beyond individual discoveries to a robust, statistically meaningful census across the entire sky. This capability is not merely about increasing the number of targets; it is about completing the parameter space required to understand the universality of planetary evolution.

Furthermore, the proposed telescope would act as a cornerstone for a multi-wavelength, multi-messenger observational ecosystem. By working in synergy with existing and upcoming northern facilities, such as the Next Generation Very Large Array (ngVLA) for radio observations and the Gaia mission for high-precision astrometry, a Northern Hemisphere giant telescope would allow for a holistic reconstruction of the physical processes driving disk evolution and planet accretion.

Ultimately, the paper presents a strategic argument for the scientific community and policymakers. Establishing this infrastructure is vital for ensuring that Europe remains at the forefront of the planetary formation revolution. The investment in a Northern Hemisphere 30-40m telescope is an investment in answering one of humanity’s most profound questions: how do planetary systems, including our own, come to be? Without this capability, our understanding of the cosmos will remain fundamentally incomplete.