Planet Formation Imager (PFI): science vision and key requirements

Abstract

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to ∼ 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs.Our preliminary results indicate that the shorter-wavelength L and M bands are optimal for detecting the circumplanetary disk in spectral line tracers. Line observations offer the prospect to detect even very low-mass

Astrophotonics: astronomy and modern optics

“…The development of multiple-telescope beam combiners is therefore indicated for the imaging of rapidly varying astronomical targets such as novae (Chesneau et al 2008) or planet transits (Kloppenborg et al 2010). While for the time being only up to 6 telescopes may be combined at existing facilities (CHARA), plans for new facilities featuring 10 (Buscher et al 2013) or 20 telescopes (Kraus et al 2016) have been proposed. CHARA is currently developing a new beam combiner in K-band which will allow to combine 3 quadruplets out of the 6 telescopes using spare components of the GRAVITY combiner (ten Brummelaar et al 2016).…”

“…Renewed interest for photonic nulling interferometry rose in recent years, stimulated by the possibility to image exoplanetary systems with interferometric techniques (Kraus et al 2016). In this context, we mention the a proof-of-principle experiment of an integrated optics 4-telescope nulling beam combiner (Errmann et al 2015) based on a scheme devised by Angel and Woolf (1997), and the aforementioned realization of an integrated optics 2x2 multimode interference coupler in chalcogenide glass (Kenchington Goldsmith et al 2017b), which was designed to achieve a deep broadband nulling level in L-band (Kenchington Goldsmith et al 2017a).…”

The path towards high-contrast imaging with the VLTI: the Hi-5 project

“…In particular, a VLTI instrument can make use of less-solicited telescopes such as the ATs to follow-up in the tIR new ELT/METIS discoveries. -PFI (Planet Formation Imager, Monnier et al 2016;Kraus et al 2016;Ireland et al 2016) is currently a science-driven, international initiative to develop the roadmap for a future ground-based facility that will be optimised to image planet-forming disks on the spatial scale where the protoplanets are assembled, which is the Hill sphere of the forming planets. The goal of PFI will be to detect and characterise protoplanets during their first ∼ 100 million years and trace how the planet population changes due to migration processes, unveiling the processes that determine the final architecture of exoplanetary systems.…”

The planet formation imager

“…After the 2014 SPIE meeting where the PFI project was introduced, a Science Working Group (SWG; headed by Stefan Kraus) and a Technical Working Group (TWG; headed first by David Buscher, and now Michael Ireland) were formed involving around one hundred astronomers around the world. Based on the early top-level science requirements first outlined in 2014, the 2016 SPIE meeting in Edinburgh saw even more contributions which explored technical solutions to achieve these science goals [17,14,12,16,19,3,21]. For instance, a mid-infrared wavelength range was chosen over mm-wave or near-infrared to access the most diverse aspects of planet formation in the "warm dust" zone.…”