exoplanet

plural exoplanets · alternative exo-planet

1. astronomyA planet which exists outside Earth's solar system.

   More such announcements will likely come in the months to follow, as the first space observatory dedicated to hunting exoplanets, called COROT, begins full operation and researchers complete their calculations.

   2007 September 1, Alexander Hellemans, “Dangling a COROT”, in Scientific American, volume 297, number 3, archived from the original on 06 Aug 2023, page 32

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   In the past two years, NASA’s Kepler Space Telescope has located nearly 3,000 exoplanet candidates ranging from sub-Earth-sized minions to gas giants that dwarf our own Jupiter. Their densities range from that of styrofoam to iron.

   2013 May-June, Kevin Heng, “Why Does Nature Form Exoplanets Easily?”, in American Scientist, volume 101, number 3, archived from the original on 07 Aug 2013, page 184

   In a first for astronomers studying worlds beyond our solar system, data from the Hubble Space Telescope have revealed water vapor in the atmosphere of an Earth-size planet. Although this exoplanet orbits a star that is smaller than our sun, it falls within what’s known as the star’s habitable zone, the range of orbital distances where it would be warm enough for liquid water to exist on a planet’s surface.

   2019 September 11, Michael Greshko, “Water found on a potentially life-friendly alien planet”, in National Geographic, archived from the original on 13 Mar 2021

   Astronomers have used two different exoplanet-detecting satellites to solve a cosmic mystery and reveal a rare family of six planets located about 100 light-years from Earth. […] Many exoplanets have been found orbiting dwarf stars that are much cooler and smaller than our sun, such as the famed TRAPPIST-1 system and its seven planets, announced in 2017.

   2023 November 29, Ashley Strickland, “Astronomers discover nearby six-planet solar system with ‘pristine configuration’”, in CNN, archived from the original on 17 Feb 2026

   Now a team of researchers is offering what it contends is the strongest indication yet of extraterrestrial life, not in our solar system but on a massive planet, known as K2-18b, that orbits a star 120 light-years from Earth. A repeated analysis of the exoplanet’s atmosphere suggests an abundance of a molecule that on Earth has only one known source: living organisms such as marine algae.

   2025 April 16, Carl Zimmer, “Astronomers Detect a Possible Signature of Life on a Distant Planet”, in The New York Times, →ISSN, →OCLC, archived from the original on 16 Apr 2025, Science

   Synonyms: exosolar planet, extrasolar planet