Observability of ultraviolet Ni lines in the atmosphere of transiting Earth‐like planets Journal Article uri icon



  • Nitrogen is a biosignature gas that cannot be maintained in its Earth‐like ratio with CO2 under abiotic conditions. It has also been proven to be notoriously hard to detect at optical and infrared wavelengths. Fortunately, the ultraviolet region, which has only recently started being explored for terrestrial exoplanets, may provide new opportunities to characterize exoplanetary atmospheric nitrogen. In this work, the future prospects for detecting atomic nitrogen absorption lines in the transmission spectrum of an Earth‐like planet orbiting in the habitable zone of a Sun‐like star with LUVOIR are explored. Using the nonlocal thermodynamic equilibrium spectral synthesis code Cloudy, we produce a far‐ultraviolet atomic transmission spectrum for an Earth–Sun‐like system and identify several nitrogen features, including both Ni and Nii lines. We calculate the number of transits required for 1σ and 3σ detections of the planetary Ni λ1200 triplet signal with the G120M grating of the LUMOS spectrograph designed for LUVOIR as a function of distance to the system and stellar ultraviolet emission. The minimum number of transit observations necessary for 1σ and 3σ detections of atomic N are 188 and 1,685, respectively, for a system located at a distance of 1 pc with 100 times the solar ultraviolet flux. Given that the orbital period of an Earth–Sun system is 1 year, it is not feasible to detect atomic N in the transmission spectrum for these systems. Future studies in this direction should therefore focus on Earth‐like planets orbiting in the habitable zone of M dwarfs.

publication date

  • November 1, 2020

has restriction

  • green

Date in CU Experts

  • January 7, 2021 5:35 AM

Full Author List

  • Young ME; Fossati L; Johnstone C; Salz M; Lichtenegger H; France K; Lammer H; Cubillos PE

author count

  • 8

Other Profiles

International Standard Serial Number (ISSN)

  • 0004-6337

Electronic International Standard Serial Number (EISSN)

  • 1521-3994

Additional Document Info

start page

  • 879

end page

  • 886


  • 341


  • 9