The exoplanet Trappist-1e has captured significant scientific and public interest as a compelling target in the ongoing search for life beyond Earth. Its discovery has fueled discussions about the potential for life around stars different from our Sun.
The Trappist-1 System and Trappist-1e’s Place
The Trappist-1 star system is located approximately 40 light-years away from Earth in the constellation Aquarius. Its central star is an ultracool dwarf, which is much smaller and cooler than our Sun, with a surface temperature of about 2,566 K (2,290 °C; 4,160 °F) and a mass of about 9% of the Sun’s mass. This star is estimated to be around 7.6 billion years old, making it older than our solar system.
Orbiting this dwarf star are seven known planets, designated Trappist-1b through Trappist-1h. The entire system is compact, with all seven planets orbiting closer to their star than Mercury orbits our Sun. Their orbital periods range from approximately 1.5 to 19 days.
Trappist-1e orbits its star every 6.10 days at a distance of about 0.029 AU (4.3 million km). Planets orbiting so close to their host stars, especially dwarf stars, are commonly tidally locked. This means one side of the planet perpetually faces the star, resulting in a permanent “day” side and a permanent “night” side.
Defining Trappist-1e
Trappist-1e is a rocky exoplanet. Its estimated radius is about 0.92 times that of Earth.
The planet’s mass is approximately 0.692 Earth masses, which is about 15% less massive than Venus. With its determined radius and mass, scientists have calculated Trappist-1e’s density to be around 4.885 grams per cubic centimeter, suggesting a solid, rocky composition.
Its estimated equilibrium temperature, assuming a blackbody with no atmosphere, is about 246.1 K (-27.1 °C; -16.7 °F). This temperature is derived from its distance from the relatively cool Trappist-1 star.
The Search for Life’s Ingredients
Trappist-1e is considered to be within its star’s “habitable zone,” sometimes referred to as the “Goldilocks zone.” This is the region around a star where conditions, particularly temperature, could allow for liquid water to exist on a planet’s surface. The presence of liquid water is considered a fundamental requirement for life as we understand it.
The planet receives about 60.4% of the stellar flux that Earth receives from the Sun, which is less than Earth but significantly more than Mars. This stellar flux contributes to its potential for liquid water. Beyond water, other factors influencing habitability include the presence of an atmosphere to regulate temperature and shield the surface, and geological activity that could recycle nutrients and release gases.
Planets orbiting dwarf stars like Trappist-1 face unique challenges. The star’s rapid rotation and frequent, powerful stellar flares, which can be thousands of times more energetic than those from our Sun, pose a threat. These flares emit intense ultraviolet (UV) radiation and strong particle winds that could strip away planetary atmospheres, potentially hindering the development or persistence of life.
Observing Trappist-1e
Scientists primarily study Trappist-1e and other exoplanets using the transit method. This technique involves observing the slight dimming of a star’s light as a planet passes in front of it from our perspective. The amount of dimming can provide information about the planet’s size.
Following detection by transit, scientists can then attempt to characterize the planet’s atmosphere. Telescopes such as the James Webb Space Telescope (JWST) are instrumental in this process, as they can analyze the light passing through a planet’s atmosphere during a transit. This analysis allows scientists to look for specific gases.
Researchers are searching for atmospheric components like water vapor, carbon dioxide, methane, and oxygen, which could serve as biosignatures, or indicators of biological activity. While Trappist-1e is confirmed to not have a cloud-free, hydrogen-dominated atmosphere, suggesting it might have a more compact, Earth-like atmosphere, no atmosphere has been definitively detected yet. This ongoing research continues to refine our understanding of Trappist-1e’s potential for habitability.