The Search Beyond Our Sun: Exoplanets from the James Webb Space Telescope

The James Webb Space Telescope under construction before its launch in 2022. (NASA)

Post Author - Erik Wells

Are we alone in the universe? Is there life beyond our solar system? And if so, what place does it hold for humans? These questions have haunted and inspired philosophers, artists, and the more existentially-minded of dorm-dwelling college students for centuries. Much of that time has been spent merely pondering these ideas, but in recent years, a select group of astronomers specializing in the field of exoplanet studies has looked to them as the driving force behind their work—and an increasing source of their frustration.

Our ability to detect exoplanets (planets outside of our solar system) increased significantly when the James Webb Space Telescope (JWST) launched in 2021. Each time a planet orbits in front of its star, the star’s brightness temporarily dims. A small amount of starlight passes through the planet’s atmosphere, where atmospheric chemicals absorb specific wavelengths and leave gaps in the spectrum of light. Using a technique known as the transit method, JWST can examine those absences for signs of carbon dioxide, water, and other molecules necessary for life to thrive.

Unfortunately, the planets most similar to Earth in size and composition are often the most difficult to observe using this method. Imagine if someone on another planet was trying to examine Earth for signs of life: we only pass in front of our sun once a year, and when we do, the sun’s sheer power means the resulting dip in brightness is practically negligible. 

As a result, scientists have broadened their search beyond solely “Earth twins” and have focused much of their attention on M-dwarfs. These are small red dwarf stars which are only 10 to 60% as big as the Sun and about 7% as bright. These stars are cool and dim, never threatening to overwhelm their planets with light even though their orbits are significantly tighter than Earth’s. Most exoplanets in these systems orbit their star at least every few weeks, and with 50 M-dwarfs to be found in the 60 stars closest to Earth, that means there’s an exoplanet in transit somewhere every few hours at most.

Of particular interest is the TRAPPIST-1 system. The planets here are tidally locked, meaning that the hemispheres are trapped in a permanent scorching heat and a constant freeze, respectively. However, between these two zones there is a thin slice of temperate climate in a state of eternal sunset (or sunrise, depending on how you look at it.) Four of these seven planets are in a potentially habitable zone, making this system our best bet to focus in on the search for a planet that could hold life.

Four of the seven planets in the TRAPPIST-1 system reside in a potentially habitable zone. (NASA/JPL-Caltech)

Around 30% of JWST’s time is devoted to exoplanet studies and only 175 hours have been spent on the TRAPPIST-1 system so far, but much has been learned already. Unfortunately, due to the temperamental nature of M-dwarfs, much of the data gathered in that time has proven undecipherable so far. Luckily, the JWST is expected to last for another 18 years, double its original 10-year life expectancy. There is still plenty of time to explore.

Searching for other habitable planets will take up a significant chunk of time before we can even start determining their habitability. According to the University of Montreal’s René Doyon, one possibility outside of the TRAPPIST-1 system is LHS 1140b, a watery “super-Earth” covered in a global ocean. LHS 1140b is the most likely to have retained an atmosphere out of Doyon’s shortlist of six planets, but it is only in transit four times a year, and with a dozen transits needed to gather enough data about carbon dioxide in the atmosphere, it would take three years before we know for sure—assuming JWST is even allocated to observe 1140b at the time of every transit.

The search for life beyond our sun is an always exciting, yet often frustrating one. But hopefully, the wait for answers will spur us to take action towards maintaining our own planet, so that we are not forced to rely on another.

Still want to explore the stars? Check out our Air & Space collection here for more on mission-flown NASA shuttles, the Apollo 11 program, and even meteorite fragments!