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Next-generation missions designed to detect biosignatures on exoplanets will also be capable of placing constraints on the presence of technosignatures (evidence for technological life) on these same worlds. Here, I estimate the detectability of nightside city lights on habitable, Earth-like, exoplanets around nearby stars using direct-imaging observations from the proposed LUVOIR and HabEx observatories. I use data from the Soumi National Polar-orbiting Partnership satellite to determine the surface flux from city lights at the top of Earths atmosphere, and the spectra of commercially available high-power lamps to model the spectral energy distribution of the city lights. I consider how the detectability scales with urbanization fraction: from Earths value of 0.05%, up to the limiting case of an ecumenopolis -- or planet-wide city. I then calculate the minimum detectable urbanization fraction using 300 hours of observing time for generic Earth-analogs around stars within 8 pc of the Sun, and for nearby known potentially habitable planets. Though Earth itself would not be detectable by LUVOIR or HabEx, planets around M-dwarfs close to the Sun would show detectable signals from city lights for urbanization levels of 0.4% to 3%, while city lights on planets around nearby Sun-like stars would be detectable at urbanization levels of $gtrsim10%$. The known planet Proxima b is a particularly compelling target for LUVOIR A observations, which would be able to detect city lights twelve times that of Earth in 300 hours, an urbanization level that is expected to occur on Earth around the mid-22nd-century. An ecumenopolis, or planet-wide city, would be detectable around roughly 50 nearby stars by both LUVOIR and HabEx, and a survey of these systems would place a $1,sigma$ upper limit of $lesssim2%$ on the frequency of ecumenopolis planets in the Solar neighborhood assuming no detections.
The detectability of planetesimal impacts on imaged exoplanets can be measured using Jupiter during the 1994 comet Shoemaker-Levy 9 events as a proxy. By integrating the whole planet flux with and without impact spots, the effect of the impacts at wa
Like the magnetised planets in our Solar System, magnetised exoplanets should emit strongly at radio wavelengths. Radio emission directly traces the planetary magnetic fields and radio detections can place constraints on the physical parameters of th
Hazes are common in known planet atmospheres, and geochemical evidence suggests early Earth occasionally supported an organic haze with significant environmental and spectral consequences. The UV spectrum of the parent star drives organic haze format
Terrestrial extrasolar planets around low-mass stars are prime targets when searching for atmospheric biosignatures with current and near-future telescopes. The habitable-zone Super-Earth LHS 1140 b could hold a hydrogen-dominated atmosphere and is a
Discs around young planets, so-called circumplanetary discs (CPDs), are essential for planet growth, satellite formation, and planet detection. We study the millimetre and centimetre emission from accreting CPDs by using the simple $alpha$ disc model