Exoplanets & Exomoons

Utilizing a Database of Simulated Geometric Albedo Spectra for Photometric Characterization of Rocky Exoplanet Atmospheres

By Keith Cowing
Press Release
September 3, 2020
Filed under
Utilizing a Database of Simulated Geometric Albedo Spectra for Photometric Characterization of Rocky Exoplanet Atmospheres
In this plot, a G2 stellar spectrum has been applied to the raw albedo spectra prior to calculating spectroscopic data from 10% filters, in order to approximate actual planetary fluxes for a planet around a solar-type star. Further, the Xand Y-axes have been changed to show the absolute difference of the filter response ratio from that of a cloud-free, pure N2 atmosphere at 1 bar P0. Included are the 3-σ noise floors for a planet at 10 parsec for 1, 3, 10, and 100 hour observations with a 15m telescope, calculated with PSG (assuming zero detector noise), which indicate how difficult it would be to distinguish between a given model and a simple world with no absorbers. Letters indicate the position of the Solar System planet analogs described in Section 3.1.

In anticipation of future flagship missions focused on the goal of achieving direct imaging of rocky exoplanets, we have developed a database of models to help the community examine the potential spectral characteristics of a broad range of rocky planet atmospheres.

Using the publicly available Planetary Spectrum Generator (PSG), we have computed a grid of 141,600 rocky exoplanet geometric albedo spectra across a 7-dimensional parameter space. Using this grid, we have performed a color-color analysis seeking to identify the most useful near-ultraviolet and red or near-infrared photometric followup channels to combine with a green-optical (discovery) spectral channel.

We found that a combination of filters at 0.4 um, 0.58 um, and (approx) 0.8um were able to distinguish between atmospheres with moderate-to-high concentrations of four different dominant absorbing constituents, given at least 10 hours of observation on a star at 10 parsec with a 15-meter-class space telescope; however, more moderate abundances similar to those of Solar System rocky bodies would be more challenging to detect. We recommend that future missions seeking to characterize directly imaged rocky exoplanets by colors alone further consider multi-band photometry as a first discriminator for planetary characteristics.

Adam J. R. W. Smith, Avi M Mandell, Geronimo L Villanueva, Michael Dane Moore

Comments: 15 pages, 10 figures. Accepted by AJ as of 9/2/2020
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2009.01330 [astro-ph.EP] (or arXiv:2009.01330v1 [astro-ph.EP] for this version)
Submission history
From: Adam J. R. W. Smith
[v1] Wed, 2 Sep 2020 20:28:33 UTC (2,444 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻