We have long wondered if we are alone in the cosmos. If there are other worlds like ours, where life might flourish. Now, a new eye in the sky has given us a glimpse of one such world. The James Webb Space Telescope has detected its first exoplanet. Its name is LHS 475b, and astronomers believe it is remarkably similar to our own home planet. It is roughly the same size as Earth, only slightly smaller by a mere 1%.
How did JWST find this distant world? As LHS 475b orbits its star, it sometimes passes in front of it, blocking some of its light. By analyzing the spectrum of that light, and measuring the decrease in brightness of the star as the planet moves in front, we can see the size and infer the density of the planet, and even infer something about its atmosphere if it has one - astronomers aren’t sure yet about that. This is the first exoplanet confirmed by this massive space telescope.
But what kind of world is LHS 475b? Is it a place where life could exist? We do not know for sure yet, but we can make some educated guesses. All we know right now are its size, distance from its star, its density and some details of its spectrum, but we can glean a few things from this small amount of information.
Because of its size, we know that it is a rocky world, not a gas giant. We know that it is very close to its star, much closer than Mercury is to our Sun. This means that it is very hot, perhaps too hot for liquid water to exist on its surface. If it has an atmosphere, the spectrum tells us it is unlikely to be rich in methane, like Titan’s. It may be more like Venus, with a thick blanket of carbon dioxide and clouds.
LHS 475b orbits a red dwarf star, one of the most common types of stars in the galaxy. It is located 41 light years away from us, in the southern constellation of Octans. It is a faint star and much cooler than our Sun. But even so, it provides enough energy for its planet to shine in the infrared spectrum. And that is how the Webb Space Telescope saw it.
This is just the beginning of our exploration of LHS 475b. We hope to learn more about its atmosphere, its climate, and its potential for life. We hope to find out if it is truly an Earth-like world, or if it is something else entirely. We hope to answer one of the oldest questions of humanity: are we alone? Or are there others out there, waiting for us to discover them?