Exoplanet also called "additional solar planet" is a planet that revolves around another star that is not our sun. The first extrasolar planets (three planets) were discovered in 1992 orbiting a pulsar star called PSR B1257 + 12 at 980 light years from Earth. It is very difficult to photograph an extrasolar planet directly, due to its great distance and also the light it reflects is very weak (remember that planets are not light generators). So far you only have a little over ten exoplanets.
The word exoplanet derives from the Greek, and is composed of the prefix "exo", which means "outside", and "planétes" which refers to "something wandering". The discovery of exoplanets is important, as it helps to expand knowledge about theories and models of star and galaxy formation.
Our Solar System that revolves around our star, the Sun, is 4.6 billion years old. The discovery of younger or more mature systems with exoplanets revolving around other stars would help determine the nature of the Solar System and the habitability of other planets.
According to the International Astronomical Union (IAU), planets outside the Solar System must orbit around a star or star remnant (white dwarf or neutron star) and have a mass less than 14 Jupiter masses. Due to their reduced mass, they do not reach temperatures and densities in their interiors high enough to fuse deuterium, an isotope of hydrogen made up of a proton and a neutron, or any other chemical element. Therefore, they do not produce energy from this type of source.
At present it has been confirmed that there are more than 500 exoplanets or extrasolar planets. On the other hand, it is believed that some of them could be located in the habitable zone, that is, that zone in which it would be possible to have liquid water on its surface.
According to astronomers and astrobiologists, if a planet contains liquid water, it is very likely that there is some form of life on it. The exoplanet Gliese 581, which is more than 20 light years from Earth, is the exoplanet with the best conditions to host any form of life.
Proxima B, an exoplanet that orbits the red dwarf star near Centauri, could be habitable because it is a rocky planet, slightly higher in mass than Earth, and within the habitable zone. The distance between Proxima B and Earth is about 4 light years, which means that reaching it with a shuttle would take about 165,000 years. To get to Proxima B more quickly, astronomers are working on a nanoprobes project that travels much faster than conventional ships and it is estimated that this could be achieved in the next 50 years.
