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Exoplanets are planets that revolve around stars other than the Sun. The first exoplanets were discovered in the 1990s, in tough competition between Swiss and American teams.

The race to find new planets had only just begun.

The cover image shows an Artistic design of a star with planets around it. Credit: ESA, web “esa.int/Science_Exploration/Space_Science/Cheops/What_are_exoplanets”

What is exactly an exoplanet?

The sun is one of billions of stars in the Milky Way and nine planets revolve around it.

It is entirely correct to assume that many of the billions of those stars in the Milky Way also have a planetary system of their own.

We call the planets of these stars “exoplanets”.

And that some of these exoplanets are inhabited by intelligent beings.

Many think that finding Earth-like planets is just a matter of time.

From the acceptance that there are thousands of civilizations similar to humanity, a lot of profound questions are raised.

One of them is is there intelligent life outside the Earth? But do not have too many illusions of being able to converse with the inhabitants of these planets.

The search for exoplanets

October 6, 1995, went down in history as the day the first extrasolar planet was discovered.

Swiss astronomers Michel Mayor and Didier Queloz discovered the first planet outside the solar system.

This discovery marked an important milestone in the history of astronomy.

The planet was cataloged as 51 Pegasi B and was assigned the name “Bellerophon”.

Exoplanets Pegaso
The exoplanet 51 Pegasi b.  Credit: ESO/M. Kornmesser/Nick Risi, web “en.wikipedia.org/wiki/51_Pegasi_b”.

The exoplanet 51 Pegasi b is approximately 50 light-years away the Earth in the constellation of Pegasus.

In recognition of his pioneering work in the search for new worlds, on June 21, 2012, the BBVA Foundation awarded its prestigious “Frontiers of Knowledge in Basic Sciences” Award to Michel Mayor and his colleague Queloz.

From 1995 to 1 January 2021, astronomers have detected in the Milky Way 4,395 exoplanets in 3,242 systems, with 720 systems having more than one planet.

There are habitable exoplanets similar to Earth

Most of these exoplanets are very large and very hot.

Planets similar to ours are currently being detected and it is thought that they could abound in the Universe.

In August 2008, NASA announced the creation of the Carl Sagan Fellowship Program for a PhD in “Exoplanets and Exploration.”

Named after the astronomer who popularized science through his books and television appearances, the program offers scholarships of about $ 60,000 to four to five scientists a year to boost the search for life on planets outside the world.

Carl Sagan. Exoplanets
Carl Sagan was one of the most prestigious scientific popularizers. Credit: BBVA, web “bbvaopenmind.com/ciencia/grandes-personajes/carl-sagan-el-defensor-del-pensamiento-critico/”

When Sagan died in 1996, only 11 exoplanets had been discovered.

The challenge is to find exoplanets that, like Earth, orbit a nearby sun.

Modern terrestrial and space telescopes, with thousands of astronomers aided even with Google’s artificial intelligence, make it possible to predict spectacular discoveries.

Gone are the heroic times of the heroes of science, such as Copernicus, Galileo, Tycho Brahe, Carolina Herschel and so many other astronomers who on lonely nights searched the skies.

That search is supported by NASA’s Kepler mission, which launched into space on March 6, 2009.

Keplerspacecraft. Exoplanets
Artist’s rendition of the Kepler spacecraft. Credit: Wendy Stenzel web “britannica.com/topic”

On September 30, 2010 an interesting news was published that a team of astronomers from the Carnegie Institution and the University of California had discovered a planet that is potentially habitable and that, due to its physical characteristics, it could harbor living organisms.

The giants exoplanets

Most known extrasolar planets are gas giants equal to or more massive than the planet Jupiter, with orbits very close to their star.

In recent years, it has begun to detect exoplanets comparable to ours.

The most Earth-like known exoplanet in mass and orbital position is Gliese 581 c, discovered in 2007 and whose mass is about 5 times the mass of Earth, and is presumed to be a large terrestrial planet.

Experts believe that this planet could have liquid water on its surface.

Gliese 581. Exoplanets
Artist’s representation of the planetary system surrounding the red dwarf Gliese 581. Credit: web “derekries.github.io/projects/xopl.html”.

In the foreground is the planet Gliese 581c which has 5 Earth masses and completes one orbit every 13 days.

The other two are Gliese 581b (Neptune-type, blue) and Gliese 581d (furthest).

Gliese 581c is just over 20 light years away. If there were a very advanced civilization there and they could focus on us right now with a super telescope, they would see us as we were 20 years ago.

From an exoplanet that is 1,000 light years away (relatively very close), they would see us as we were 1,000 years ago (they would think we are a little behind).

Obviously, we could not start a conversation with them similar to the one we can have with the neighbor on the balcony across the street.

Super earth

The term super-earth is used to refer to an extrasolar terrestrial planet that has between one and ten times the mass of the Earth and between 1.25 to 2 radii of the Earth.

In addition, most of them are very close to the star they orbit, as a planet of significant size far away from it would have lost less gas in its formation and would have resulted in a gas giant.

The first discovery of a planet of these characteristics was carried out in 2005 by a team led by Eugenio Rivera, the planet in question being Gliese 876 d,  and since then more super-earths have been discovered.

Gliese 667 Cc is a super-earth exoplanet discovered on November 21, 2011 by the HARPS spectrograph, and its existence confirmed on February 2, 2012,

Super Earth. Exoplanets
Artistic image of Gliese 667 Cc that orbits the star Gliese 667 C. Credit: ESO / L. Calçada, web “es.wikipedia.org/wiki/Gliese_667_Cc”.