Designed before scientists knew much about exoplanets, JWST luckily has the right instruments to determine the atmospheric composition of Earth-like exoplanets. Until now, scientists have been using other telescopes, including Hubble’s infrared instruments, to observe enormous, Jupiter-sized exoplanets. Because of their size, these larger exoplanets are more easily spotted (but researchers have reason to suspect that they aren’t the most common exoplanets in the universe).
JWST will extend out exoplanet observation capabilities, allowing scientists not only to peer at larger Jupiter-sized planets, but also investigate climate and habitability on smaller, Earth-like rocky worlds orbiting small, cool, and often active red dwarf stars.
In addition to expanding exoplanet research, JWST will allow astronomers to observe some of the earliest stars and galaxies, which scientists think formed just a hundred million years or so after the Big Bang. As the universe expands, their light becomes redder as its wavelength stretches out — a phenomenon known as cosmological redshift.
Because of this, the light emitted from the most distant objects, billions of light-years away, stretches into the infrared portion of the spectrum. This primordial light will enter JWST’s state-of-the-art mirror — designed to pick up these longer wavelengths — and get sent to the infrared instruments aboard the telescope for analysis. Studying these early galaxies will provide clues to what our universe was like in its infancy.
From there, JWST can examine the evolution of galaxies. Why do we have the variety of galactic structures we see today? What is the nature of galaxies and the supermassive black holes that sit at their hearts? By looking at galaxies throughout the history of the universe, from early days to the present, astronomers will be able to start answering these questions.