Here are some of the most exciting discoveries of Earth-like planets in distant worlds.
In February 2012, an international team of scientists reported the results of their wobble-based research focused on GJ 667C, an M-class dwarf star associated with two other orange dwarfs located about 22 light-years from Earth. The astronomers were hoping to learn more about a previously discovered super-Earth (GJ 667Cb) with an orbital period of just 7.2 days, but their observations led to something better — GJ 667Cc, another super-Earth with an orbital period of 28 days. The planet, which sits comfortably in the Goldilocks zone of GJ 667C, receives 90 percent of the light that Earth receives. Most of this light is in the infrared spectrum, which means the planet likely absorbs a higher percentage of the energy coming to it. The bottom line: GJ 667Cc may absorb the same amount of energy from its star that Earth soaks up from the sun and may, as a result, support liquid water and life as we know it. Later observations detected that the planet was extremely hot and thus not likely good for habitation.
Kepler-452b, often referred to as Earth’s “cousin,” is an exoplanet located approximately 1,400 light-years away from us. Discovered by NASA’s Kepler spacecraft in 2015, it was the first near-Earth world found within the habitable zone of its star, Kepler-452, where conditions could be favorable for the existence of liquid water on its surface. It is one of the Kepler planets. Kepler-452b has a diameter about 1.6 times that of Earth, and orbits its star in a similar fashion, taking around 385 days to complete one orbit. These are zones within which liquid water can exist on a planet’s surface.
The TRAPPIST-1 system, discovered in 2016 has seven planets orbiting a small, cool star known as TRAPPIST-1. Situated about 40 light-years away, this system ignited excitement because it was the largest collection of Earth-sized planets ever found outside our solar system. All seven planets orbit much closer than Mercury does to our sun, yet their location within the star’s habitable zone offers the possibility of liquid water on their surfaces. These exoplanets, named TRAPPIST-1b to TRAPPIST-1h, also seemed to be rocky. Some are tidally locked, always showing the same face to their star. This means that one side of the planet is in permanent daylight with scorching sun, while the other side is in permanent freezing darkness. But after further investigation, it appears that TRAPPIST-1e may be the only planet in the system still hospitable to life; the rest are either too close or too far from their star.
GJ 1002b and GJ 1002c
Other habitable zone planets are GJ 1002b and GJ 1002c which orbit the red dwarf star GJ 1002, located approximately 16 light-years away from Earth. These rocky planets have about the same mass as Earth. GJ 1002b takes around 10 days to orbit its star, while GJ 1002c takes just over 21 days. The two planets were discovered in 2022.
In early 2023, NASA announced the discovery by TESS of TOI 700e, a planet about the same size as our own. While its composition remains unknown, scientists speculated that it could have a rocky surface like Earth. Being located within the zone of habitable planets could allow it have liquid water, too. TOI 700e takes 28 days to orbit its star and may be tidally locked. (For comparison, our moon is tidally locked to our Earth, but Earth is not tidally locked to the sun, its star.)
In other words, even with the basic parameters we just mentioned, there’s a lot more to consider before we can truly call a planet “Earth-like.” Missions like the James Webb Space Telescope, which can see the atmospheres of exoplanets, might tell us a lot more.
This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.