Astrophysical research into exoplanets has delivered thousands of confirmed planets orbiting distant stars. These planets span a wide range of size and composition, with diversity also being the hallmark of system configurations, the great majority of which do not resemble our own solar system. Unfortunately, only a handful of the known planets have been characterized spectroscopically thus far, leaving a gaping void in our understanding of planetary formation processes and planetary types. To make progress, astronomers studying exoplanets will need new and innovative technical solutions. Astrophotonics – an emerging field focused on the application of photonic technologies to observational astronomy – provides one promising avenue forward. In this paper we discuss various astrophotonic technologies that could aid in the detection and subsequent characterization of planets and in particular themes leading towards the detection of extraterrestrial life.
The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed to directly detect and characterize young, Jupiter-mass exoplanets. After six years of operation at Gemini South in Chile, the instrument is being upgraded and relocated to Gemini North in Hawaii as GPI 2.0. GPI helped establish that Jovian-mass planets have a higher occurrence rate at smaller separations, motivating several sub-system upgrades to obtain deeper contrasts (up to 20 times improvement to the current limit), particularly at small inner working angles. This enables access to additional science areas for GPI 2.0, including low-mass stars, young nearby stars, solar system objects, planet formation in disks, and planet variability. The necessary instrumental changes required toenable these new scientific goals are to (i) the adaptive optics system, by replacing the current Shack-Hartmann Wavefront Sensor (WFS) with a pyramid WFS and a custom EMCCD, (ii) the integral field spectrograph, by employing a new set of prisms to enable an additional broadband (Y-K band) low spectral resolution mode, as well as replacing the pupil viewer camera with a faster, lower noise C-RED2 camera (iii) the calibration interferometer, by upgrading the low-order WFS used for internal alignment and on-sky target tracking with a C-RED2 camera and replacing the calibration high-order WFS used for measuring and correcting non-common path aberrations with a self coherent camera, (iv) the apodized-pupil Lyot coronagraph designs and (v) the software, to enable high-efficiency queue operations at Gemini North. GPI 2.0 is expected to go on-sky in early 2024. Here I will present the new scientific goals, the key upgrades, the current status and the latest timeline for operations.
The Photonic Lantern (PL) is a novel optical technology consisting of a multi-mode fiber adiabatically merged to several single-mode fibers. PLs efficiently split light into its individual modes, revealing both phase and amplitude information. This makes them attractive for use in focal plane wavefront sensing and spectroscopy. Spectro-astrometry, a technique that involves searching for wavelength-dependent centroid shifts in spectrally-dispersed datasets, can be conducted with PLs to resolve circumstellar structures with extremely small angular separations that are not accessible with traditional imaging techniques. Here, we investigate the application of PLs for spectro-astrometry of young stars hosting protoplanetary disks with embedded accreting planets. Although spectro-astrometry of point-source accreting companions with PLs has been numerically explored in the past, those simulations did not include the effects of scattered light by the protoplanetary disk. We carry out numerical simulations of accretion signatures inside protoplanetary disks to understand the feasibility of using PLs to detect accreting planets under realistic conditions. We simulate the response of a 6 port PL to young stars with a circumstellar disk containing an accretion hotspot centered on the Paschen beta hydrogen line. We discuss the lower limit of the hotspot-to-star contrast detectable by a PL in the context of contamination by disk signals after introducing both random and systematic noise sources. The simulations also demonstrate the effects of scattered light by the circumstellar disk on the PL response to an embedded accreting protoplanet with a fixed planet-to-star contrast.
The Earth’s turbulent atmosphere results in speckled and blurred images of astronomical objects when observed by ground based visible and near-infrared telescopes. Adaptive optics (AO) systems are employed to reduce these atmospheric effects by using wavefront sensors (WFS) and deformable mirrors. Some AO systems are not fast enough to correct for strong, fast, high turbulence wind layers leading to the wind butterfly effect, or wind-driven halo, reducing contrast capabilities in coronagraphic images. Estimating the effective wind speed of the atmosphere allows us to calculate the atmospheric coherence time. This is not only an important parameter to understand for site characterization but could be used to help remove the wind butterfly in post processing. Here we present a method for estimating the atmospheric effective wind speed from spatio-temporal covariance maps generated from pseudo open-loop (POL) WFS data. POL WFS data is used as it aims to reconstruct the full wavefront information when operating in closed-loop. The covariance maps show how different atmospheric turbulent layers traverse the telescope. Our method successfully recovered the effective wind speed from simulated WFS data generated with the soapy python library. The simulated atmospheric turbulence profiles consist of two turbulent layers of ranging strengths and velocities. The method has also been applied to Gemini Planet Imager (GPI) AO WFS data. This gives insight into how the effective wind speed can affect the wind-driven halo seen in the AO image point spread function. In this paper, we will present results from simulated and GPI WFS data.
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