The universe is vast, and thinking that we are alone in it is stupid because there is an unimaginable number of planets, some of which are habitable planets, and as we know from Earth, life requires at least water and a habitable temperature, so we will look for planets that are habitable and at least have to be the size of Earth.
Planets Where Alien life Could Be Possible
Kepler-22b is a super-Earth with a superocean. The jury is still out on Kepler-22b’s true nature; at 2.4 times the radius of the Earth, it could potentially be gaseous. According to current computer simulation, an ocean world tipped on its side – similar to our solar system’s ice giant, Uranus – turns out to be reasonably habitable.
Researchers discovered that an exoplanet in the Earth’s size range, at a comparable distance from its sun and covered in water, might have an average surface temperature of roughly 60 degrees Fahrenheit (15.5 Celsius). Because of its extreme tilt, the planet’s north and south poles would be alternately drenched in sunlight and darkness for half a year as it circled its star.
Kepler-452b is the first near-Earth-size world to be found in the habitable zone of a star that is similar to our sun. Until its discovery in 2015, the Kepler telescope had only detected 12 Earth-size planets (smaller than twice the size of Earth) in the habitable zone of their smaller and cooler stars. Kepler-452b is the first planet orbiting a star about the same size and temperature as the sun.
When looking for planets that might support life, scientists start with the habitable zone. The habitable zone is a region around a star where temperatures are right for water—an essential ingredient for life as we know it—to pool on the surface. Scientists don’t know if Kepler-452b can support life. What is known about the planet is that it is about 60 percent larger than Earth, placing it in a class of planets dubbed “super-Earths,” with an orbit of 385 days. Scientists believe that Kepler-452b is about 6 billion years old, much older than Earth.
TRAPPIST is a unique star system, TRAPPIST-1 e is a terrestrial exoplanet that orbits an M-type star. Its mass is 0.62 Earths, it takes 6.1 days to complete one orbit of its star, and is 0.02817 AU from its star. Its discovery was announced in 2017.
TRAPPIST-1 f is another planet sitting in the habitable zone of the TRAPPIST system. TRAPPIST-1 f is a super-Earth exoplanet that orbits an M-type star. Its mass is 0.68 Earths, it takes 9.2 days to complete one orbit of its star, and is 0.0371 AU from its star. Its discovery was announced in 2017.
The planet is very likely tidally locked, with one hemisphere permanently facing towards the star, while the opposite side is shrouded in eternal darkness. However, between these two intense areas, there would be a sliver of moderate temperature – called the terminator line, where the temperatures may be suitable (about 273 K or 0 °C or 32 °F) for liquid water to exist. Additionally, a much larger portion of the planet may be habitable if it supports a thick enough atmosphere to transfer heat to the side facing away from the star.
TRAPPIST-1 g is a super-Earth exoplanet that circles an M-type star. It has a mass of 1.34 Earths, takes 12.4 days to complete one orbit around its star, and is 0.0451 AU away from it. It was discovered in 2017 and was announced.
TRAPPIST-1g could feature a vast water ocean or a supercritical ice atmosphere. According to a simulation of magma ocean-atmosphere interaction, TRAPPIST-1g is believed to have retained a large fraction of the primordial steam atmosphere throughout the early stages of evolution, and hence has a thick ocean covered by an atmosphere containing hundreds of bars of abiotic oxygen today.
Kepler-186f is an exoplanet that orbits the red dwarf Kepler-186, approximately 500 light-years (178.5 parsecs, or nearly 5.01015 kilometers) from Earth. It is the first planet identified in another star’s habitable zone with a radius similar to Earth’s.
Kepler-186f’s size is known to be less than 10% that of Earth, but its mass, composition, and density remain unknown. Previous research indicates that a planet the size of Kepler-186f is most likely rocky. Before this finding, Kepler-62f held the “record” for the most “Earth-like” planet, which is 40% larger than Earth and circles in its star’s habitable zone.
Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone. If you could stand on the surface of Kepler-186f, the brightness of its star at high noon would appear as bright as our sun is about an hour before sunset on Earth.