More than 4,000 exoplanets have been discovered since 1995, when a planet like Earth was discovered orbiting a sun-like star. More than half of these discoveries were made thanks to the Kepler Space Telescope, which started working in 2009 to determine whether there is another planet with Earth-like life conditions in the Milky Way Galaxy.
Discovering a habitable planet with conditions similar to planet Earth has been a long-standing dream of astronomers. It has been proven that there are small, rocky worlds like Earth in the galaxy, although they do not have exactly the same features with the recently discovered exoplanets. Let’s take a look at the 10 most Earth-like exoplanets ever discovered.
How is a planet classified as ‘earth’?
First of all, let’s take a look at what is required for a planet to be classified as a habitable world. To put it very simply, for a planet to be considered potentially life-friendly, it must be relatively small and rocky, and orbit its star in what has been described as the “habitable zone”, where water can be found on its surface in liquid form.
On the other hand, with the further development of existing telescopes with the developing technology, it will be possible to deal with other factors such as the atmospheric composition of the planet and how active its main star is in addition to these factors.
Here are 10 potentially life-friendly Earth-like exoplanets
Gliese 667Cc
Discovered with the European Southern Observatory’s 3.6-metre telescope in Chile and located just 22 light-years from Earth, according to NASA’s Jet Propulsion Laboratory, Gliese 667Cc is at least 4.5 times larger than our planet. This exoplanet, which completes one orbit around its host star in just 28 days, is thought to be in the habitable zone due to the fact that this star is a much cooler red dwarf than the sun.
But of course, the planet is also likely to orbit close enough to overheat from the heat from the red dwarf.
Kepler-22b
Located 600 light-years away, Kepler-22b is the first Kepler planet to be in the habitable zone of its main star. However, it is unknown for now whether the planet, which is approximately 2.4 times larger than Earth, is rocky, liquid or gas.
On the other hand, Kepler-22b orbiting its star in 290 days is very close to Earth’s 365-day cycle. However, although the exoplanet orbits a G-class star like our sun, this star is known to be smaller and cooler than Earth’s.
Kepler-69c
Having completed its orbital cycle in 242 days, Kepler-69c’s position in the solar system is similar to that of Venus in our system. This exoplanet appears to be in the habitable zone because its host star is 80 percent as bright as the Sun.
But let’s face it, Kepler-69c, which is approximately 2,700 light-years away, is 70 percent larger than Earth. For this reason, scientists currently have no idea about the component of the planet.
Kepler-62f
According to NASA, Kepler-62f orbits a star that is about 40 percent larger than Earth and much cooler than our sun. But its 267-day orbit makes Kepler-62f a member of the habitable zone class. Kepler-62, the star of this exoplanet, which orbits its red dwarf star much closer than Earth does to the sun, produces much less light.
About 1,200 light-years from Earth, Kepler-62f’s size makes it a rocky planet with potential oceans.
Kepler-186f
Kepler-186f is located approximately 500 light-years from Earth. Kepler-186f, which is at most 10 percent larger than Earth; It appears to be in the habitable zone of its star, although it is slightly out of the way.
Due to its main star being a red dwarf, Kepler-186f cannot be said to be a true twin of Earth. In addition, this exoplanet gets only one-third of the energy that Earth receives from the sun from its star.
Kepler-442b
Discovered 1,194 light-years away in 2015 and 33 percent larger than Earth, according to NASA, Kepler-442b orbits its star every 112 days.
A study published in 2021 claims that this exoplanet could receive enough light to sustain a large biosphere. According to researchers who analyzed the possibility of different planets to photosynthesize, Kepler-442b is receiving enough radiation from its star.
Kepler-452b
This world, whose discovery was announced in 2015, is the first planet in size close to Earth to orbit a sun-sized star, according to NASA. Kepler-452b, 60 percent larger than Earth and 10 percent larger than its main star, the sun; It is very similar to our sun and is located in the habitable zone.
According to the data obtained, Kepler-452b, which is 1.6 times the size of the Earth, is just as likely to be rocky. Located 1,400 light-years away, Kepler-452b’s orbit around its star takes only 20 days longer than Earth, and completes in 385 days.
Kepler-1649c
Kepler-1649c, which has similar dimensions to Earth, is located in the habitable zone orbiting its star. Located 300 light-years away and only 1.06 times larger than Earth, this exoplanet receives 75 percent of the light that Earth receives from the sun from its star.
Proxima Centauri b
Located just 4 light-years from Earth, Proxima Centauri b stands out as the closest known exoplanet to Earth. The mass of the exoplanet, discovered in 2016, is 1.27 times that of Earth.
On the other hand, although it is in the habitable zone of its star, this exoplanet is exposed to extreme ultraviolet radiation. The reason for this is that the planet is very close to its star and completes its orbit in 11.2 days.
TRAPPIST-1e
The planets orbiting the star TRAPPIST-1 are the most Earth-sized planets ever discovered in a single star’s habitable zone. However, it is quite possible that the water on most of the planets in this planetary system consisting of seven worlds has evaporated.
Some planets in the system may also have more water than Earth’s oceans, according to a 2018 study. In particular, it is estimated that the world named TRAPPIST-1e in the system has a very high probability of supporting life.
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