Extraterrestrial (TV program)

Lore & Background

The documentary is based on speculative collaboration of a group of American and British scientists, collectively commissioned by National Geographic. For the purposes of the series, the team divided two hypothetical examples of realistic worlds on which extraterrestrial life could evolve: a tidally locked planet dubbed 'Aurelia' orbiting a red dwarf star, and a large moon dubbed 'Blue Moon' orbiting a gas giant in a binary star system. The scientific team used a combination of accretion theory, climatology, and xenobiology to imagine the most likely locations for extraterrestrial life and the most probable evolutionary path such life would take.

The first episode focuses on Aurelia, a hypothetical Earth-sized extrasolar planet orbiting a red dwarf star. The scientists theorized that aiming the Terrestrial Planet Finder at a red dwarf star might yield the best opportunities for seeing smaller planets. They tested traditional assumptions that a tidally locked planet might be incapable of holding an atmosphere, and their estimations suggested such a planet could hold on to its atmosphere, though with unusual results. The second episode presents Blue Moon, a large moon orbiting a gas giant in a binary star system.

Reader's Guide

Extraterrestrial (Alien Worlds) is significant for its attempt to ground speculative alien biology in contemporary science, using input from a team of American and British scientists. The series modeled two plausible exoplanetary environments—a tidally locked world around a red dwarf and a moon in a binary star system—and constructed hypothetical ecosystems based on accretion theory, climatology, and xenobiology. The concepts of Aurelia and Blue Moon were later featured in the touring exhibition The Science of Aliens. The documentary also highlighted the challenges of detecting Earth-like exoplanets, noting that the Terrestrial Planet Finder project was all but canceled due to U.S. congressional spending limits. By focusing on red dwarf stars and binary systems, the series addressed the statistical likelihood that many habitable worlds may exist in environments very different from Earth's, and it preserved scientific uncertainty where appropriate, such as the disputed status of Gliese 581g.

Did You Know?

• The series features two fictional worlds: Aurelia (a tidally locked planet) and Blue Moon (a large moon in a binary star system).
• The scientific team assumed that most extraterrestrial life would be carbon-based, an assumption sometimes called carbon chauvinism.
• The concepts from the series were featured in the touring exhibition The Science of Aliens.