TOI-700 is a

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

101.4 light-years away from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

located in the

Dorado Dorado () is a constellation in the southern sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the dolphinfish (''Coryphaena hippurus''), which is known as ''dorado'' in Spanish, altho ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

that hosts TOI-700 d, the first Earth-sized

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

in the

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kas ...

discovered by the

Transiting Exoplanet Survey Satellite Transiting Exoplanet Survey Satellite (TESS, Explorer 95 or MIDEX-7) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the ''Kepler' ...

(TESS).

Nomenclature and history

The acronym "TOI" refers to stars and exoplanets studied by TESS, and is short for: "Transiting Exoplanet Survey Satellite Object of Interest".

Stellar characteristics

TOI-700 is a red dwarf of spectral class M (much redder, cooler, and dimmer than the sun) that is 40% the mass, 40% the radius and 55% of the temperature of the Sun. The star is bright with low levels of stellar activity. Over the 11 sectors observed with TESS, the star does not show a single white-light

flare A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, ...

. The low rotation rate is also an indicator of low stellar activity.

Planetary system

Four exoplanets have been detected by TESS to be orbiting the host star TOI-700. All four exoplanets may be

tidally locked Tidal locking between a pair of co-orbiting astronomical body, astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where ...

to TOI-700. Three papers describe the validation of the planetary system, the follow-up observations of TOI-700 d with the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

and the characterization of TOI-700 d. The composition of planets b and d is more likely

rocky ''Rocky'' is a 1976 American sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the ''Rocky'' franchise and stars Talia Shire, Burt Young, Carl Weathers, and Burgess M ...

and the composition of planet c is more likely similar to that of

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

. The two inner planets might have grown faster and accreted significant gaseous envelopes, but the outer planet formed more slowly and accreted less gas. The innermost planet may later have lost its envelope due to

photoevaporation Photoevaporation denotes the process where energetic radiation ionises gas and causes it to disperse away from the ionising source. This typically refers to an astrophysical context where ultraviolet electromagnetic radiation, radiation from hot st ...

. Another scenario that could explain the arrangement of densities in this system is long-term

planetary migration Planetary migration occurs when a planet or other body in orbit around a star interacts with a disk of gas or planetesimals, resulting in the alteration of its orbital parameters, especially its semi-major axis. Planetary migration is the most l ...

. Planet c might have migrated inwards, but this scenario is more plausible if future studies show that planet c is significantly more massive than planet b or d. TOI-700 d lies in the

. It receives 35 times more

EUV Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths from 124 nm down to 10 nm, and therefore (by the Planck– ...

photons than Earth, but also 50 times less than

TRAPPIST-1 e TRAPPIST-1e, also designated as 2MASS J23062928-0502285 e, is a rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1 approximately away from Earth in the constellation of Aquarius. ...

. The host star has low stellar activity. The atmosphere of a planet with an Earth-like pressure would survive for longer than 1 Gyr. Simulations of the planet have shown that TOI-700 d is a robust candidate for a habitable world. The simulated spectral feature depths from transmission spectra and the peak flux and variations from synthesized phase curves do not exceed 10 ppm. This will likely prohibit JWST from characterizing the atmosphere of TOI-700 d. In November 2021, a fourth possible planet, Earth-sized and receiving approximately 30% more flux from TOI-700 than earth does from the Sun, was found at the inner edge of the habitable zone of TOI-700. In January 2023 the existence of this planet, designated 700 e, was confirmed. Discovered in 2023, TOI 700 e is terrestrial exoplanet that NASA claims to be an "earth-like" planet. Discovered by NASA's TESS (Transitioning Exoplanet Survey Satellite), TOI 700 e has mass of about 0.818 Earths and takes 27.8 days to orbit once around its star. The planet is in a habitable zone distance from the M-type star TOI 700 it orbits, leading NASA scientists to believe that there is potential for liquid water on its surface. Ten percent smaller than its neighboring planet TOI 700 d, both are at a distance from their sun to be considered habitable, however, TESS requires an additional year to acquire more data about the exoplanets. Being one in only about a dozen habitable zone planets known, further research and data collection of the TOI 700 solar system is important for understanding Earth-like planets. The system is near (but not in) orbital resonance: from planets b to d, period ratios are approximately 5:8, 4:7, 3:4.

Notes

References

External links