Since the discovery of the first exoplanet in 1992, thousands more have been discovered. Forty light-years away, such a system of exoplanets was discovered orbiting a star known as Trappist-1.
Studies using the James Webb Space Telescope have revealed that one of the planets, Trappist-1 b, has a crust that appears to be changing. Geological activity and weathering are a likely cause, and if the latter is the case, it indicates that the exoplanet also has an atmosphere.
Exoplanets are planets that orbit other stars. By all accounts, they vary in size, composition, and distance from their star. Finding them is quite a tricky endeavor and a number of different approaches are used.
Since the first discovery, more than 5,000 exoplanets have been found and now the hunt is of course on to find planets that could support life. Likely candidates would orbit their host star in a region known as the habitable zone, where the temperature is just right for a life-sustaining world to evolve.
There are three exoplanets in the Trappist-1 system that orbit the star within the habitable zone; Trappist-1st, f and g. The star is a cool dwarf star in the constellation Aquarius and was identified in 2017 as a host of exoplanets.
The discoveries were made using data from NASA’s Kepler Space Telescope and the Spitzer Space Telescope. The system is named after the Transiting Planets and PlanetesImals Small Telescope (TRAPPIST.)
A team of researchers from the Max Planck Institute for Astronomy and the Commissariat aux Énergies Atomiques (CEA) in Paris studied Trappist-1b. They used the James Webb Space Telescope’s Mid-Infrared Imager to measure the exoplanet’s thermal radiation.
Their findings have been published in the journal Nature Astronomy. Previous studies concluded that Trappist-1b was a dark rocky planet and had no atmosphere. The new study has turned this conclusion on its head.
The measurements found by the team revealed something else. They found a world with a surface composed largely of unchanged material. Typically, the surface of a world without an atmosphere is weathered by radiation and peppered with meteorite impacts.
The study found that the surface material is about 1,000 years old, much younger than the planet itself, which is believed to be several billion years old.
The team hypothesizes that this could indicate volcanic activity or plate tectonics, as the planet is sufficiently large to still retain the internal heat from its formation. It is also possible that the observations reveal a thick atmosphere rich in carbon dioxide.
The observations initially suggested that there was no carbon dioxide layer, as they found no evidence of thermal radiation absorption. However, they have run models to show that atmospheric haze can reverse the temperature profile of a carbon dioxide-rich atmosphere.
Normally the warmest area is the ground, but in the case of Trappist-1b the atmosphere may absorb radiation, heating the upper layers, causing the infrared energy itself to be radiated. A similar process can be seen on Saturn’s moon Titan.
Fortunately, the alignment of the planetary system means that it passes directly in front of the star, so spectroscopic observations and dimming of the starlight as the planet passes in front of it can reveal the profile of the atmosphere.
Further studies are now underway to investigate this and make further observations to determine the nature of the atmosphere around Trappist-1b.
