Exoplanets: new worlds to discover
Are we alone in the universe? Is there a chance to colonize other planets outside our solar system? These are just some of the most frequent questions scientists all around the world have asked themselves throughout the years. Indeed, since 1992 NASA has started to search for exoplanets relying on indirect methods, such as looking at the stars themselves for signs that planets might be orbiting them.
Exoplanets – or extrasolar planets, as the name suggests – are planets outside our solar system. As of today, more than 5000 exoplanets have been confirmed to exist. Some are massive, like Jupiter, but orbit much closer to their host star than Mercury does to our Sun. Others are rocky or icy, and many simply do not have analogues in our Solar System. There are systems hosting more than one planet, a planet orbiting two stars, and a handful of planets that may even have the right conditions for water to be stable on their surfaces, an essential ingredient for life as we know it.
Nowadays the possibility to colonize one of those planets isn’t so remote, which is why NASA last year realized some advertising posters to promote guided tours on some of those possible new earths. And you, which one would you choose?
Kepler 16-b
Kepler-16b was Kepler telescope’s first discovery of a planet in a “circumbinary” orbit, which means that it circles two stars, as opposed to one star in a double-star system. Like Luke Skywalker's home planet Tatooine, Kepler-16b would have two sunsets if you could stand on its surface. This planet, however, is likely cold, about the size of Saturn and gaseous, though partly composed of rock. It lies outside its two stars’ habitable zone, where liquid water could exist. And its stars are cooler than our sun, probably rendering the planet lifeless.
Kepler-186f
Kepler-186f is the first Earth-size planet discovered in the potentially habitable zone around another star, where liquid water could exist on the planet's surface. Its star is much cooler and redder than our Sun. If plant life does exist on a planet like Kepler-186f, its photosynthesis could have been influenced by the star's red-wavelength photons, making for a color palette that's very different from the greens on Earth. This discovery was made by Kepler, NASA's planet hunting telescope.
PSO J318.5-22
Discovered in October 2013 using direct imaging, PSO J318.5-22 belongs to a special class of planets called rogue, or free-floating, planets. Wandering alone in the galaxy, they do not orbit a parent star. Not much is known about how these planets came to exist, but scientists theorize that they may be either failed stars or planets ejected from very young systems after an encounter with another planet. These rogue planets glow faintly from the heat of their formation. Once they cool down, they will be dancing in the dark.
-Maggio 2023-
TRAPPIST-1e
Some 40 light-years from Earth, a planet called TRAPPIST-1e offers a heart-stopping view: brilliant objects in a red sky, looming like larger and smaller versions of our own moon. But these are no moons. They are Earth-sized planets in a spectacular planetary system outside our own. These seven rocky worlds huddle around their small, dim, red star, like a family around a campfire. Any of them could harbor liquid water, but the planet shown here, fourth from the TRAPPIST-1 star, is in the habitable zone, the area around the star where liquid water is most likely to be detected.
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