Astronomers continue to discover worlds beyond Earth’s solar system, detecting hundreds of new ones each year in the vastness of space.
The number of confirmed exoplanets — planets that don’t orbit the sun — has currently risen to 5,638, according to NASA, with thousands more under review. These worlds exist in our galactic neighborhood, though scientists using the Chandra X-ray Observatory think they detected a planet outside the Milky Way for the first time.
This growing tally is only a tiny sampling of planets. With hundreds of billions of galaxies, the universe probably teems with many trillions of stars. And if most stars have at least one orbiting planet — well, don’t let your heads explode.
The more scientists find, the more they learn that no two alien planets are alike, each harboring its own distinct chemistry and conditions. There are water worlds, planets with multiple sunsets, volcanic worlds, and planets with clouds unlike anything found in Earth’s skies.
With the powerful James Webb Space Telescope, getting to know these worlds should become easier. The leading infrared space observatory, run by NASA in partnership with the European and Canadian space agencies, spends about a quarter of its time studying exoplanets. Knowing what’s in another planet’s atmosphere can tell scientists a great deal about a world, including whether it could be hospitable to life.
Super-Earth world with a mysterious sibling
A world somewhat larger than our own, known as a “super-Earth,” orbits a star not far (relatively speaking) from this solar system — about 137 light-years away. What has astronomers intrigued with the exoplanet, dubbed TOI-715 b, is its location in the habitable zone around its small reddish star. The habitable zone, sometimes referred to as the Goldilocks zone, is the region around a host star thought to provide the right surface temperature for liquid water to exist.
But perhaps even more exciting than TOI-715 b, which orbits its star every 19 days, is its potential sibling: a smaller, more Earth-size planet. Scientists can’t wait to learn more about it.
Cooler, less-horrifying Venus-like planet
Credit: NASA / JPL-Caltech / R. Hurt (Caltech-IPAC) illustration
Scientists say they’ve found the nearest temperate Earth-size world to date: Gliese 12 b, a so-called exo-Venus, meaning a rocky planet outside the solar system about the size of Venus.
“Temperate” and “Venus” may seem contradictory to those who know about Earth’s neighbor. It’s a hot, toxic planet, with sulfuric acid rain and volcanoes. But Venus might once have looked a lot more like Earth, with oceans and less oppressive heat. Unlike the real Venus, which is about 900 degrees Fahrenheit because of a runaway greenhouse effect, researchers think Gliese 12 b’s surface could be an average of 107 degrees.
Two-faced world, half-swimming in lava
Credit: NASA / JPL-CALTECH illustration
Scientists found an exoplanet just a little larger than Earth, with a star much like the sun. But that’s pretty much where the similarities end. The planet, HD 63433 d, is one-tenth Earth’s age, exponentially hotter, and likely molten lava on one side. A year on this world would fly by in just four Earth days.
It’s the smallest and closest “young” exoplanet known so far, at only 73 light-years away. Astronomers estimate it’s about 400 million years old, which is ancient on a human timescale, but a mere whippersnapper compared to our 4.5 billion-year-old home planet.
Terrestrial planet glowing like campfire embers
Credit: NASA / ESA / CSA / Dani Player (STScI) illustration
In a star system 66 light-years away, scientists spotted a world riddled with so many volcanoes, it would glow red-hot. A researcher even described the finding, HD 104067, as “Io on steroids,” referring to the most volcanic world in our solar system, one of Jupiter’s moons, Io.
HD 104067’s robust volcanic activity is caused by two other nearby exoplanets exerting strong gravitational forces and distorting its orbit into an egg shape. All that squeezing and tugging generates heat and inner geological activity.
Rocky exoplanet with some atmosphere?
Credit: NASA / JPL-Caltech illustration
When astronomers say they are on a quest to find a rocky planet with an atmosphere, they’re not talking about mood lighting and soft jazz. They’re looking for a world that resembles our own in a crucial way, and scientists say super-Earth 55 Cancri e might be the best bet: Temperature readings have revealed it’s not as scorching hot as expected, perhaps because energy is being redistributed by an atmosphere.
NASA has called Earth’s own atmosphere its security blanket. Without it, the type of life flourishing here wouldn’t exist. It holds oxygen in the air, filters out ultraviolet radiation, and allows liquid water to exist on the surface.
But this finding wouldn’t mean 55 Cancri e, about 41 light-years away, is an exit plan for Earth — far from it. Its orbit is so tight around its star, the world is probably covered in lava, with one side in constant darkness. Still, with more observations, 55 Cancri e could turn out to be the first rocky planet with an atmosphere scientists find outside our solar system.
