TOI-1338 b

TOI-1338 b (also known as BEBOP-1 b or EBLM J0608-59 b) is a Saturn-sized exoplanet orbiting the binary star system TOI-1338. It is a circumbinary planet, meaning it orbits both stars. The planet and its two stars are located in the constellation Pictor, about 1,300 light-years (400 parsecs) from Earth. It is the innermost planet of the TOI-1338 planetary system, orbiting the stars' center of mass every 95 days at an average distance of 0.46 astronomical units (AU; 69 million km or 43 million mi). The planet has an average temperature of 630 K (357 °C; 674 °F). When viewed from Earth, the planet transits or passes in front of its parent stars and blocks out some of their light, allowing it to be detected by telescopes. TOI-1338 b was first detected by the Transiting Exoplanet Survey Satellite (TESS) in 2018 and recognized in 2019 by teenage NASA intern Wolf Cukier. It was the first circumbinary exoplanet discovered in TESS observations. Observations have shown that the planet has a radius close to Saturn's and a mass smaller than Uranus's, which gives it a very low density of around 0.14 g/cm3. This low density makes TOI-1338 b as a super-puff, a type of exoplanet thought to have a small core surrounded by a substantial amount of gas. Although the composition of TOI-1338 b is currently unknown, the James Webb Space Telescope is expected to determine the composition of its atmosphere with observations to be made in September 2026.

Discovery TOI-1338 b was first observed by the Transiting Exoplanet Survey Satellite (TESS) during routine observations of the sky beginning in 2018. TESS detected the planet when it transited a star and temporarily dimmed its brightness, repeating every time it orbits the star. The star system where the planet was found, TOI-1338, is an eclipsing binary system containing two stars that revolve around each other and periodically eclipse from Earth's point of view. Due to the eclipsing binary nature of the star system, their eclipses often obscure the planet's transits and their orbital motion causes the planet's transits to occur and last irregularly. Finding these hidden planet transits posed a challenge for computer algorithms at the time, so astronomers resorted to visually inspecting the TESS data by eye. Wolf Cukier, a 17-year-old attending Scarsdale High School in New York at the time, joined the NASA Goddard Space Flight Center in 2019 to work as a summer intern for his mentors Ravi Kopparapu and Veselin Kostov. Cukier was tasked with finding circumbinary planet transits in TESS data flagged by volunteers of the online Planet Hunters TESS citizen science project. On his third day of interning, while visually inspecting TESS observations of TOI-1338, Cukier found an unknown transit that did not line up with the star's eclipses. Cukier suspected that the transit was caused by a planet and alerted Kostov of his finding, who then confirmed it with the help of astronomers Jeremy Orosz, Adina Feinstein and Bill Welsh. Additional transits by the planet were found in TESS data, and the planet's gravitational influence on its parent stars was detected in archival radial velocity measurements by the La Silla Observatory. The discovery of the planet, now known as TOI-1338 b, was announced on 6 January 2020 at the 235th American Astronomical Society meeting in Honolulu, Hawaii, becoming the first circumbinary planet discovered in TESS data. Cukier, his mentors, and various collaborators co-authored a paper describing the discovery, which was published in The Astronomical Journal in May 2020.

Name

The planet's name follows the exoplanet naming convention of taking the parent star's name and adding a lowercase letter after it. As it is the first exoplanet discovered orbiting the TOI-1338 star system, it is named TOI-1338 b. The initialism "TOI" stands for "TESS Object of Interest", which is systematically given to the star system when TESS confirms a planet transiting it. Astronomers have also called the planet BEBOP-1 b and EBLM J0608-59 b, after the Binaries Escorted By Orbiting Planets (BEBOP) and Eclipsing Binary, Low Mass (EBLM) surveys that observed the star system, respectively. Wolf Cukier had mentioned in interviews that his brother and family suggested naming the planet Wolftopia, though Cukier admitted that he was content with keeping the planet's original designation.

SOPHIE renaming petition In February 2021, Christian Arroyo launched a petition on Change.org calling for NASA to rename TOI-1338 b to SOPHIE, in honor of the late British musician Sophie. The planet was chosen because fans of Sophie pointed out that NASA's depiction of TOI-1338 b resembled the cover art of Sophie's Oil of Every Pearl's Un-Insides album. The petition amassed over 95,000 signatures and was supported by Charli XCX and Caroline Polachek. Although it was unsuccessful in officially renaming the planet, the International Astronomical Union announced in June 2021 that the name Sophiexeon was officially given to the asteroid (10026) 1980 RE1.

Parent stars and location

The parent stars of TOI-1338 b are a binary system consisting of a large, F-type main-sequence star, and a small, red dwarf star. The larger star of the binary system, named A or the primary star, is hotter (temperature 6030 K), brighter (luminosity 2.1 L☉), and larger (radius 1.32 R☉, mass 1.13 M☉) than the Sun. The smaller star of the binary system, named B or the secondary star, is cooler (temperature 3300 K), dimmer (luminosity 0.009 L☉), and smaller (radius 0.31 R☉, mass 0.31 M☉) than the Sun. The two stars, collectively known as TOI-1338 (or BEBOP-1 or EBLM J0608-59), orbit each other every 14.6 days and are mutually separated by an average distance of about 0.13 astronomical units (20 million km or 12 million mi). The TOI-1338 system is known to host two circumbinary planets, which are named TOI-1338 b and TOI-1338 c. Together, TOI-1338 and its planetary system are located in the southern constellation of Pictor, at a distance of about 1,300 light-years (400 parsecs) from Earth. Viewed from Earth, TOI-1338 appears at an apparent magnitude of 11.7, which is too faint to be seen with the naked eye or a small telescope.

Planetary properties

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