(Artistic rendition, image via webbtelescope.org)

Volunteer Writer: Mckenzie Ferrari

Email: mferrari@umassd.edu

The James Webb Space Telescope (JWST), which launched on December 25th, 2021, has finally started to send its results to Earth after over a year of collecting and transmitting data. 

The JWST is the largest optical telescope in space; its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Space Telescope.

On January 11th, 2023, a team of researchers led by Kevin Stevenson and Jacob Lustig-Yaeger from John Hopkins University confirmed the first observed exoplanet using JWST. 

While this is certainly not the first confirmed exoplanet ever, the findings show how detailed and revolutionary the results from JWST truly are.

How do we even detect planets orbiting stars?

There are multiple ways, but the most common method is to detect the transit, or crossing, of the planet in front of its host star. 

If looking in the sky at a star in orbit, the planet temporarily blocks a small section of the star’s surface as a planet passes in front of the star in your line of sight. This causes a detectable dip in brightness. From this dip, astronomers can infer lots of information, including the planet’s orbital period and the relative masses of the star and planet.

Stevenson and Lustig-Yaeger focused their efforts on LHS 475b, a planet that is about 99% the mass of our Earth. 

After only two transit observations, JWST’s Near-Infrared Spectrograph (NIRSpec) captured evidence of the planet. 

While confirming LHS 475b is a rocky, terrestrial planet like Earth, the team also discovered that it has an orbital period of just two days, in contrast to Earth’s 365-day orbit. This is because LHS 475b orbits close to its host star, which is a red dwarf star. 

Because red dwarf stars are very cool temperature-wise, the habitable zone — where water can exist in a stable liquid on the surface — lies much closer to the star. 

In principle, some of these exoplanets orbiting red dwarfs stars could be habitable.

What else do we know about exoplanets?

Much like how there are nitrogen and oxygen present in our atmosphere, it is believed that many of these planets’ atmospheres have common elements or gasses, such as water vapor or carbon dioxide. 

Before the JWST, researchers were limited to exoplanets they could observe the atmospheres of, meaning that only exoplanets larger than Jupiter could be characterized.

Of all currently operating telescopes, JWST is the only one capable of characterizing the atmospheres of smaller, Earth-sized planets. 

LHS 475b is one of the first Earth-sized exoplanets to have its atmosphere analyzed. Or at least attempted to be analyzed.

During this first observation of the planet, JWST did not observe detectable quantities of a particular element or molecule.

While the team has not been able to state definitively what atmosphere LHS 475b has, they do know that it cannot have a thick methane-dominated atmosphere, which is similar to the atmosphere of Saturn’s moon Titan. 

The team also found that the planet is a few hundred degrees warmer than Earth, which could suggest that LHS 475b has an atmosphere similar to Venus, which is covered in thick clouds and has a carbon dioxide atmosphere.

More observations by the team will be made this summer to obtain more data and information about LHS 475b’s atmosphere.

While this work is ongoing, it demonstrates the technological capabilities of the new JWST and marks the beginning of a new chapter for Earth-like exoplanet discovery.