Our imagination is often tied to down-to-Earth experiences. To calibrate what we might expect from the war zone of an Earth-twin, let us consider a plausible scenario for our own planet.
In her book titled “Nuclear War: A Scenario”, the brilliant journalist Annie Jacobsen describes a realistic scenario in which North Korea first launches a nuclear ballistic missile towards Washington, D.C., shortly followed by a missile from a submarine towards a nuclear power plant in California. In retaliation, the U.S. sends nuclear ballistic missiles over the North Pole and Russian airspace. Consequently, Russia misinterprets this move and decides to launch 900 nuclear warheads towards the U.S. This escalation triggers the U.S. and NATO allies to target their full warhead stockpile at Russia. This doomsday scenario could result in explosions totaling the equivalent of a few thousand megaton of TNT in a matter of a couple of hours. Assuming a radiative efficiency of order 50%, a global nuclear war of this magnitude would result in a radiation flare with a total luminosity of about 10^{15} Watts, which is about a percent of the total luminosity of sunlight reflected from Earth.
Given that the nuclear war’s glow would have unique signatures in ultraviolet and infrared light and last for a few hours, the extraterrestrial flare resulting from Annie’s scenario on an Earth-twin could potentially be distinguished from stellar flares by UV observations with the Hubble Space Telescope or infrared data from the Webb telescope. For a nearby Earth-twin within a distance of a few tens of light years, space telescopes can potentially separate the planetary flare spatially from the location of the star. Masking the bright starlight is challenging but potentially feasible for faint dwarfs, the most common type of stars.
Not unitl after it happened long ago.
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