find all the exoplanets that we can

While there are still people who do not finish seeing with good eyes that Pluto is not a planet, astronomers have been compiling an extensive list of exoplanets. How many exoplanets includes this list? Many, thousands of fact. The number of exoplanets that we discover grow month by month.

Exoplanets passionate many for different reasons, but with total security, the most widespread reason must be the possibility, remote but real, that one day we will find life in one of them. The more exoplanets we identify and study, the greater the probability of running out of our planet and our solar system.

But let’s start with the basics: What is an exoplanet? Well, an exoplanet is essentially a planet, with the only peculiarity of orbiting a star other than ours, although there is something to clarify in this.

Because The definition of a planet is that of a spatial object that orbits a star but that must have two additional characteristics: one, sufficient mass to acquire a spherical shape; and the other, also to be of sufficient size to clear their orbit of similar objects. This last criterion is what made Pluto lost the planet category.

Check if these criteria are fulfilled, at distances of thousands of light years, it is difficult. The smallest exoplanets discovered, as Kepler-37bthey have a size similar to that of the moon, so we can assume that they are spherical. The problem is that it can become more difficult to check if an explanet of this size is accompanied by a similar but more difficult object to detect in the same orbit.

Types of exoplanets

Study objects at such distances is complicated but we know that they are not very different from those that we can find in our environment. That is why we usually classify these distant objects using analogies Based on the planets that we know best.

The smaller exoplanets usually enter the category of rock exoplanets or terrestrial. These exoplanets are similar not only to Earth but to planets inside the Solar System such as Mercury, Venus or Mars. The next category would be that of superstierras, rocky planets such as ours but larger. Sometimes this category It intermingles with the subcategory of the mini-neptuna.

The following category is that of the planets similar to Neptune, also comparable in size to Uranus, these planets normally have atmospheres full of hydrogen or helium, mini-neptuna are sometimes also classified in this category. Finally we have the gaseous giants similar to Jupiter and Saturn (or even larger), which sometimes includes the subcategory of the “hot júpiteres”.

The closest

If we want to find an exoplanet we don’t have to go very far. In astronomical terms, of course: the closest exoplanets of which we have news orbit the stars closest to ours, next Centauri. This system has at least one planet, next Centauri B, and also with at least one not confirmed partner, next centauri d.

In theory there could be even closer exoplanets, although they would be virtually impossible to detect. For a few decades we have proof of the existence of wandering or interstellar planets, objects of mass similar to that of a planet that does not orbit any star but also but They roam the galaxy.

The most similar to Earth

The answer to the question of what is the exoplanet most similar to Earth depends on the criteria we use. The size and its position in the “habitable zone” of the star orbits are the main criteria that we can establish to determine the degree to which a planet can be similar to ours. The dough is usually related to the fact that this planet has a rocky surface, while the fact that it is in the habitable area implies the possibility that the planet has liquid water like ours.

Following these criteria, We can highlight for example Kepler-1649c. Located about 300 light years from our planet, Kepler-1649C has a mass 1.06 times that of the Earth and, although it receives about 75% of the solar energy that reaches our planet we can place it within the area of ​​habitability of its star.

Another good candidate is Kepler-442b. It is located at 1,194 light years of the earth and is 33% greater than the Earth, but its orbital situation would allow not only the existence of water but also the photosyntos.

Special mention deserves next Centauri B, the planet closest to Earth is not only in the habitable zone of its star, it also has a size relatively similar to ours, 27% higher in mass.

How many exoplanets are there?

Let’s go back to the question we started, how many exoplanets we have discovered. According to the most recent data available, NASA’s exoplanet file list It includes a total of 5,926 exoplanets. Something more than a third of them, 2.28 specifically, They are classified As similar to Neptune, and only 217 are categorized as “land” (although the number of superstar is much larger, 1,741).

However, we have only torn the surface. To the list of confirmed exoplanets we can add one, even greater, of candidate objects, more than 15,000 in total. And again this is only the beginning: our galaxy has tens or hundreds of billions of stars, we do not know how many of them could house planets.

In addition, almost all the exoplanets discovered so far are found precisely within the Milky Way, so we do not know anything about the number of exoplanets that could be orbiting in the observable universe.

Is there life in exoplanets?

The big question that many have asked ourselves numerous throughout our life still has no answer. The possibility of life in solar systems distant from ours grows with each new discovery but we still have no evidence of the existence of life, even less intelligent life, on planets outside our solar system (or in another other than ours).

However, The search continues.

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Image | NASA/JPL-CALTECH/R. Hurt