TRAPPIST-1c is an exoplanet of significant scientific interest, one of seven known planets orbiting the ultracool dwarf star TRAPPIST-1. This system has become a prime target for exoplanetary research due to its proximity to Earth and the presence of multiple potentially Earth-sized planets. Advanced telescopes, including the James Webb Space Telescope, are used for observations, with TRAPPIST-1c currently under intense scrutiny.
Understanding TRAPPIST-1c
TRAPPIST-1c orbits TRAPPIST-1, an ultracool dwarf star located approximately 40.7 light-years from Earth in the constellation Aquarius. It is the third most massive and third largest planet within its system, with a radius about 1.10 times that of Earth and a mass approximately 1.31 times Earth’s mass. The planet’s density suggests a primarily rocky composition, similar to the terrestrial planets in our own solar system.
TRAPPIST-1c completes an orbit around its host star in just 2.42 days. Due to its close proximity to TRAPPIST-1, the planet is likely tidally locked, meaning one side perpetually faces its star while the other remains in constant darkness. Despite orbiting so close, TRAPPIST-1c receives about 2.1 times the amount of sunlight Earth receives, comparable to Venus in our solar system.
Atmosphere and Potential for Life
Recent observations have provided insights into TRAPPIST-1c’s atmosphere. Data from the James Webb Space Telescope (JWST) announced in 2023 suggests the planet does not possess a thick carbon dioxide atmosphere similar to Venus. This finding is based on measurements of the heat energy emitted from TRAPPIST-1c’s dayside.
The absence of a thick atmosphere affects the planet’s surface conditions, particularly the potential for liquid water. A substantial atmosphere would redistribute heat from the dayside to the nightside, resulting in a lower dayside temperature. However, the measured dayside temperature of approximately 380 Kelvin (about 107 degrees Celsius or 225 degrees Fahrenheit) makes TRAPPIST-1c the coolest rocky exoplanet characterized by thermal emission using the James Webb Space Telescope. This high dayside temperature, coupled with the lack of heat redistribution, suggests that liquid water on the surface is unlikely.
While a thick carbon dioxide atmosphere has been largely ruled out, the possibility of a very thin atmosphere or a bare rocky surface remains. Some models explore the potential for a thin, oxygen-rich atmosphere, possibly with small amounts of carbon dioxide or water vapor, or even a steam atmosphere resulting from water loss. Understanding TRAPPIST-1c’s atmospheric properties is a step in assessing the habitability of the TRAPPIST-1 system, as atmospheres are crucial for supporting life.
Unveiling TRAPPIST-1c’s Secrets
Scientists gather information about exoplanets like TRAPPIST-1c through advanced astronomical instruments. The James Webb Space Telescope (JWST) plays a significant role in these investigations, particularly in analyzing atmospheric composition and measuring temperatures. For TRAPPIST-1c, JWST’s Mid-Infrared Instrument (MIRI) measured the heat emitted from its dayside. This was achieved by observing the planet as it moved behind its star, an event known as a secondary eclipse. By comparing the combined light of the star and planet with the light from just the star during the eclipse, astronomers isolate the light, and thus the heat, coming from the planet itself.
The transit method is another technique used to detect exoplanets and study their atmospheres. This method involves observing the slight dimming of a star’s light as a planet passes in front of it. The amount of light blocked provides information about the planet’s size, while repeated transits reveal its orbital period. While direct imaging of these small, close-in planets is not currently possible with JWST, the telescope can search for and probe their atmospheres as they transit. Ongoing research continues to refine our understanding of TRAPPIST-1c and the other planets in its system, with future observations aimed at further constraining atmospheric properties and exploring habitability.