[20] The name is a reference to the TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST)[12][d] project that discovered the first two exoplanets around the star.

[24] Its planetary system was discovered by a team led by Michaël Gillon, a Belgian astronomer[25] at the University of Liege,[26] in 2016[27] during observations made at the La Silla Observatory, Chile,[28][29] using the TRAPPIST telescope.

[66] It is expected to shine for ten trillion years—about 700 times[67] longer than the present age of the Universe[68]—whereas the Sun will run out of hydrogen and leave the main sequence[n] in a few billion years.

[121] The photospheric features of the star may introduce inaccuracies in measurements of the properties of TRAPPIST-1's planets,[70] including their densities being underestimated by 8+20   -7 percent,[122] and incorrect estimates of their water content.

These interactions could force periodic or episodic full rotations of the planets' surfaces with respect to the star on timescales of several Earth years.

[134] Vinson, Tamayo and Hansen (2019) found the planets TRAPPIST-1d, e and f likely have chaotic rotations due to mutual interactions, preventing them from becoming synchronised to their star.

[135] Other processes that can prevent synchronous rotation are torques induced by stable triaxial deformation of the planets,[ab] which would allow them to enter 3:2 resonances.

[142] For the outer planets Quick et al. (2020) noted that their tidal heating could be comparable to that in the Solar System bodies Europa, Enceladus and Triton,[143] and may be sufficient to drive detectable cryovolcanic activity.

[167] A synchronously rotating planet might not entirely freeze over if it receives too little radiation from its star because the day-side could be sufficiently heated to halt the progress of glaciation.

[176] Intense extreme ultraviolet (XUV) and X-ray radiation[177] can split water into its component parts of hydrogen and oxygen, and heat the upper atmosphere until they escape from the planet.

[178] In the case of TRAPPIST-1, different studies with different assumptions on the kinetics, energetics and XUV emissions have come to different conclusions on whether any TRAPPIST-1 planet may retain substantial amounts of water.

[189] Stellar energetic particles would not create a substantial radiation hazard for organisms on TRAPPIST-1 planets if atmospheres reached pressures of about 1 bar.

The planet is outside the habitable zone;[216] its expected irradiation is more than four times that of Earth[216] and the James Webb Space Telescope (JWST) has measured a brightness temperature of 508+26−27 K on the day side.

[217] TRAPPIST-1b has a slightly larger measured radius and mass than Earth but estimates of its density imply it does not exclusively consist of rock.

[218] Owing to its black-body temperature of 124 °C (397 K), TRAPPIST-1b may have had a runaway greenhouse effect similar to that of Venus;[79] JWST observations indicate that it has either no atmosphere at all or one nearly devoid of CO2.

[219] Based on several climate models, the planet would have been desiccated by TRAPPIST-1's stellar wind and radiation;[220][221] it could be quickly losing hydrogen and therefore any hydrogen-dominated atmosphere.

[234] Several climate models suggest that the planet may[220] or may not have been desiccated by TRAPPIST-1's stellar wind and radiation;[220] density estimates, if confirmed, indicate it is not dense enough to consist solely of rock.

[120][249] TRAPPIST-1g may have retained masses of water equivalent to several of Earth's oceans;[79] density estimates of the planet, if confirmed, indicate it is not dense enough to consist solely of rock.

[266][267] The formation conditions of the planets would give them large initial quantities of volatile materials,[194] including oceans over 100 times larger than those of Earth.

[268] If the planets are tidally locked to TRAPPIST-1, surfaces that permanently face away from the star can cool sufficiently for any atmosphere to freeze out on the night side.

[269] This frozen-out atmosphere could be recycled through glacier-like flows to the day side with assistance from tidal or geothermal heating from below, or could be stirred by impact events.

[287] If the planets have an atmosphere, the amount of precipitation, its form and location would be determined by the presence and position of mountains and oceans, and the rotation period.

[288] Planets in the habitable zone are expected to have an atmospheric circulation regime resembling Earth's tropical regions with largely uniform temperatures.

[290] The emission of extreme ultraviolet (XUV) radiation by a star has an important influence on the stability of its planets' atmospheres, their composition and the habitability of their surfaces.

[260] While in this state, it would have been considerably brighter than it is today and the star's intense irradiation would have impacted the atmospheres of surrounding planets, vaporising all common volatiles such as ammonia, CO2, sulfur dioxide and water.

[336] The discovery of the TRAPPIST-1 planets drew widespread attention in major world newspapers, social media, streaming television and websites.

[340] The dynamics of the TRAPPIST-1 planetary system have been represented as music, such as Tim Pyle's Trappist Transits,[341] in Isolation's single Trappist-1 (A Space Anthem)[342] and Leah Asher's piano work TRAPPIST-1.

[343] The alleged discovery of an SOS signal from TRAPPIST-1 was an April Fools prank by researchers at the High Energy Stereoscopic System in Namibia.

The original discoverers were affiliated with universities spanning Africa, Europe, and North America,[372][373] and the discovery of TRAPPIST-1 is considered to be an example of the importance of co-operation between observatories.

The speculative Breakthrough Starshot proposal for sending small, laser-accelerated, uncrewed probes would require around two centuries to reach TRAPPIST-1.