April 21, 2023

The ExoExplorer Science Series presents talks by cohort members Evelyn MacDonald (U Toronto) & Clarissa Do O (UC San Diego) on April 21, 2023, from 11 AM - 12 PM Pacific / 2 PM - 3 PM Eastern. Connection information is below.

Speaker: Clarissa Do O (UC San Diego)

Title: Constraining the Formation of Directly Imaged Exoplanets By Upgrading the Gemini Planet Imager (GPI)’s Wavefront Sensor

Abstract: 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 (~1-10 AU), and their formation pathways are still not completely understood. These questions motivate several sub-system upgrades to obtain deeper contrasts particularly at small inner working angles. One of GPI 2.0’s upgrades will be on its adaptive optics system, by replacing the current Shack-Hartmann wavefront sensor (WFS) with a pyramid WFS and a custom EMCCD. Electron multiplying CCDs (EMCCDs) are detectors capable of counting single photon events at high speed and high sensitivity. The upgraded ultra low-noise wavefront sensor is expected to give the adaptive optics (AO) system the capability to achieve high Strehl ratios on stars two magnitudes fainter than the current limit. GPI 2.0 is expected to go on-sky in late 2025. Here I will present on GPI 2.0’s science goals, its adaptive optics upgrades and the latest timeline for operations and current status.

Speaker: Evelyn MacDonald (U Toronto)

Title: Ambiguities in transit spectra of habitable zone rocky planets due to unknown surface conditions

Abstract: JWST will produce transit spectra of several habitable zone rocky planets orbiting M-dwarfs in the coming years. To provide context for interpreting observations, I use a 3D climate model combined with a radiative transfer model to generate synthetic transit spectra for a synchronously rotating rocky planet over a large parameter space of possible climates. Since it will be difficult to constrain a planet’s surface conditions empirically, I systematically vary the planet’s land cover and atmosphere mass in order to characterize the climate uncertainties associated with these parameters. These variations result in a large range of possible climate states featuring significant differences in surface temperature and humidity. I will show that planets in different climate regimes can have similar transit spectra, which means that it will likely be difficult to measure a given planet’s liquid water inventory or the size of its temperate region using transit spectroscopy. Land cover and atmosphere mass are therefore important sources of climate uncertainty to account for when interpreting JWST spectra.

Meeting link:
Meeting number:
2763 643 6746