Webb and Exoplanets
Yet, we still have much to learn about these alien worlds — and they have much to teach us.
The first exoplanets astronomers discovered were quite puzzling. Some orbited a pulsar — a highly magnetized stellar corpse that expels lethal amounts of radiation into space. Other exoplanets were the size of Jupiter — or larger — orbiting extremely close to their host stars.
In the years since, astronomers have found other types of planets that don't exist in our solar system. There are "super-Earths" and "mini-Neptunes" that are bigger than our home planet, but smaller than the next-largest member of our solar system, Neptune. And there are "super-Jupiters" that are much more massive than the largest planet in our solar system, Jupiter.
Astronomers have also found planets that orbit pairs of stars rather than single stars, and other planets orbiting "failed" stars called brown dwarfs that aren't mighty enough to produce light and energy (or carry out fusion) like normal stars do.
The Webb telescope could find answers within the disks of dust and gas that surround many young stars in our galaxy. Such disks are where planets are born. However, the secrets of these disks are mostly hidden away from telescopes that observe only visible light. Whereas dust and gas block visible light, infrared light given off by objects veiled in gas and dust can be detected. Webb's infrared vision will detect objects in these disks, observing how minuscule bits of ice and rock grow into larger bodies, and perhaps revealing how and where embryonic planets take shape.
And because planets tend to glow brighter in infrared light than in visible light, Webb will help astronomers discover even more exoplanets than we know of today. Webb will be able to find planets that remain unnoticed by visible-light telescopes. It could even provide images of young, Jupiter-like planets orbiting other stars.
Plus, Webb will take us a step further — not only finding exoplanets, but helping to reveal what these worlds are like. When a planet passes in front of its parent star, Webb will be able to determine the planet's size by measuring how much starlight the planet blocks. By examining starlight that passes through a planet's atmosphere, Webb will be able to learn what the atmosphere is made of by recording the unique chemical "signatures" imprinted on the starlight by different elements and molecules in the atmosphere. If Webb is unable to find evidence of certain constituents that astronomers expect to find in a planet's atmosphere, it could reveal that the planet has clouds blocking Webb's view. Brightness variations that Webb detects in a planet's atmosphere could give us details about the kind of weather the planet experiences.