It may be that in the distant future, exoplanets similar to our world will be the refuge of humanity after the end of the Earth.
Of the little more than 4 thousand exoplanets found so far, the worlds that most attract the attention of scientists and the general public are the super earths: rocky planets that by their characteristics are similar to Earth.
Super Earths seem more common than previously thought in 1995, when the first exoplanet. To our knowledge, more than a thousand worlds discovered by NASA’s Kepler Space Telescope are super-earths that have between twice and up to ten times the size of the earth, in addition to a rocky composition similar to that of the inner planets of the Solar System.
These two characteristics differentiate them from the rest and approximate their composition to that of our world; However, the way a super-earth can be considered a habitable planet goes beyond its composition and size.
Habitability zone: the distances that could harbor life
The most important requirement for a super-earth to have the potential to host life similar to that we know on Earth is that it be in a habitable zone regarding its star.
For a planet to be within the habitable zone, it is not only necessary that the distance at which it orbits from its star is not so far that it is an icy and inhospitable world, nor so close that high temperatures result in a perpetual greenhouse effect, like Venus.
The habitable zone also depends on the energy that the star gives off and the period of planet rotation are able to maintain the conditions of temperature for the existence of a atmospheric pressure enough to protect the surface of the radiation and at the same time, ensure the existence of liquid water inside.
The most Earth-like planets
One of the most revealing findings about super-lands is K2-18b, a planet twice the diameter of Earth that orbits within the habitable zone of the star K2-18.
And although we still know little about this world (discovered in mid-2019), K2-18b has liquid water on its surface, in addition to maintaining an average temperature of between zero and 40 degrees Celsius, the most similar to our planet ever discovered.
Another super-earth with characteristics similar to our planet is Kepler 438b. Located 473 light years from the Solar System, this world was considered one of the main candidates to host extraterrestrial life after its discovery in 2015, due to its incredible similarity both in size (1.12 times the Earth’s radius) and in the average climate of 37.4 degrees Celsius with the Earth; however, a short time later it was dismissed due to the immense radiation from its star.
More recently, a couple of months ago an investigation by the University of Göttingen revealed the existence of two super-earths in the system formed by the star Gliese 887, located eleven light years from our Sun.
However, even though the two planets GJ 887b and GJ 887c have a solid core between 4 and 7 times the size of the Earth respectively, both are located exactly outside the inner limit of the habitable zone of Gliese 887.
Although at first glance the requirements for the existence of planets very similar to Earth seem almost impossible to fulfill, in the little time we have to observe worlds beyond our cosmic neighborhood we have verified the existence of some super-earths that lead us to think that more than a unique and special condition of our planet, the Universe could be a space brimming with life.
Animation showing the incredible speed of light in the Solar System
Astronomers capture the first photograph in the history of a Solar System like ours