Adaptive Optics in High-Contrast Imaging

Abstract

The development of adaptive optics (AO) played a major role in modern astronomy over the last three decades. By compensating for the atmospheric turbulence, these systems enable to reach the diffraction limit on large telescopes. In this review, we will focus on high contrast applications of adaptive optics, namely, imaging the close vicinity of bright stellar objects and revealing regions otherwise hidden within the turbulent halo of the atmosphere to look for objects with a contrast ratio lower than 10 −4 with respect to the central star. Such high-contrast AO-corrected observations have led to fundamental results in our current understanding of planetary formation and evolution as well as stellar evolution. AO systems equipped three generations of instruments, from the first pioneering experiments in the nineties, to the first wave of instruments on 8m-class telescopes in the years 2000, and finally to the extreme AO systems that have recently started operations. Along with highcontrast techniques, AO enables to reveal the circumstellar environment: massive protoplanetary disks featuring spiral arms, gaps or other asymetries hinting at ongoing planet formation, young giant planets shining in thermal emission, or tenuous debris disks and micron-sized dust leftover from collisions in massive asteroid-belt analogs. After introducing the science case and technical requirements, we will review the architecture of standard and extreme AO systems, before presenting a few selected science highlights obtained with recent AO instruments.

Speckle lifetime in XAO coronagraphic images: temporal evolution of SPHERE coronagraphic images

“…For all these reasons, we tried to detect any influence of the hour angle in our analysis, as it was done for VLT/NaCo data. 19 We therefore binned the on-sky data of 3087s into four batches of 13min each and calculated the evolution of the correlation coe cient over time for each batch. The result is shown in Fig.…”

Kernel phase imaging with VLT/NACO: high-contrast detection of new candidate low-mass stellar companions at the diffraction limit

“…Detecting exoplanets from the ground using these techniques has only been made possible by the recent development of extreme adaptive optics systems (e.g. Milli et al 2016) and is mainly limited by non-common path aberrations which are not sensed by the wavefront control system (e.g. Sauvage et al 2007).…”

Advanced technologies and instrumentation and the National Science Foundation

“…Multi-Conjugate Adaptive Optics (MCAO) uses multiple wavefront sensors to achieve wide-field correction; notably 1407957/Goode recently led to the first demonstration of MCAO in solar imaging [18]. Extreme Adaptive Optics (ExAO) is a recent evolution of single-conjugated AO systems to achieve high contrast at short separations from a bright star for exoplanet searches [19]. The MagAO system on the Magellan/Clay telescope was supported by ATI (1206422/Close), and its upgrade to an ExAO system is supported by an active ATI award (1506818/Males).…”