Whether it is a volcanic apocalypse, the collision of an asteroid, the cooling of the nucleus, the growth of the sun or climate change, it is likely that if we manage to remain alive as a species, sooner or later we will have to abandon our beloved planet. I already know that we are not used to (and, in many ways, we are not prepared to) plan for such a long-term, but, even if it is only as an exercise, the question is stimulating. In the first place, we should know what is the reason for our departure. In case the problem goes further and the neighborhood becomes uninhabitable, we would have to leave the Solar System. Luckily, the search for exoplanets (planets outside the Solar System) has undergone an exciting advance in recent years. With some doubtful precedent, the first exoplanet was discovered in 1992 and the first 'resemblance' to Earth, in 1995.

Exoplanet

It is called an extrasolar planet or exoplanet to a planet that orbits a star different from the Sun - that is, we speak of another star - and that, therefore, is not part of our Solar System. In 1995 Michel Mayor and Didier Queloz discovered by means of indirect detection methods the first extrasolar planet orbiting a star belonging to the sequence of the main sequence - HR diagram. Since then, the discoveries of these new planets have been happening at a very fast rate.

Most known extrasolar planets are gaseous giants equal or more massive than the planet Jupiter, with orbits very close to its star and very short orbital periods, also known as hot Jupiters. It is believed that this tendency of supermassive planets is a little result of the current method of detection, which planets of this type more easily find than smaller terrestrial planets. With all this panorama, the exoplanets comparable to ours begin to be detected, according to the current detection capabilities, newly applied technologies, new instruments in orbit and the time of study is in continuous growth.

Source
Public Domain

The Future uncovered with the Exoplanets

The European Space Agency (ESA) will study the nature of planets that orbit stars in other systems with the Ariel mission (Atmospheric Remote-sensing Infrared Exoplanet Large-survey), ESA's fourth middle-class scientific mission, which will launch in the middle of 2028. This mission has been chosen by ESA as part of its Cosmic Vision plan. Ariel intends to answer one of the key themes of this plan: what are the conditions for the formation of planets and the birth of life.

Thousands of exoplanets have already been discovered with all kinds of masses, sizes, and orbits, but there does not seem to be a pattern that links these characteristics to the nature of the progenitor star. In particular, it is unknown how the chemistry of the planet is associated with the environment in which it was formed or if the type of progenitor star conditions the physics and chemistry in the evolution of that planet. Thus, Ariel will address fundamental questions about the composition of exoplanets and the formation and evolution of planetary systems, investigating the atmospheres of hundreds of planets orbiting different types of stars, which will allow assessing both the properties of specific planets and groups of planets.

The observations of these worlds will allow obtaining information about the first phases of planetary and atmospheric formation, as well as their subsequent evolution, which in turn will contribute to putting the Solar System in context. Thanks to Ariel, European scientists will be able to maintain their competitive advantage in this dynamic field. In addition, the mission will be based on the experiences and knowledge acquired in previous exoplanetary missions.

Source. Logotype of the European Space Agency (ESA) Public Domain

The star Trappist-1

39 light years from Earth is the star Trappist-1, known at NASA by the catalog name 2MASS J23062928-0502285. That is, a star completely irrelevant until very recently. Last May, the team led by Michaël Gillon (University of Liege, Belgium) already announced that it had discovered two exoplanets (maybe three) orbiting it. With 9% of the mass of the Sun, Trappist-1 is a cold red dwarf. If it were a little smaller, it would no longer be a star but a brown dwarf, which are cold stars that can not fuse hydrogen like our sun.

The seven exoplanets of the Trappist-1 system are rocky and could have large amounts of water on their surface, whether liquid, in the form of vapor, or as an ice crust, according to an international research led by the University of Bern (Switzerland). ) that for the first time has measured the densities of the planets. According to the data published in the latest issue of the journal Astronomy & Astrophysics, Trappist-e, the fourth world of the system, is the most similar to Earth and the best candidate to house liquid water and life.

The Trappist-1 system, 39 light-years from our Sun, rose to fame in February of last year, when it was announced that it contained seven worlds of a size similar to Earth - never before have planets such as ours been discovered around us. of the same star. Astronomers identified them by observing that the dwarf star Trappist-1 experiences tiny eclipses on a regular basis: a signal that something intervenes between it and Earth periodically. The data revealed that that something must be seven planets.

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Creative Commons Attribution 4.0

Since the mid-1990s, when the first planet was discovered around a sun-like star, astronomers have amassed what is now a large collection of exoplanets: almost 3,500 have been confirmed to date. Researchers have classified these planets in much the same way that biologists identify new animal species and thereby have learned that most of the exoplanets found to fall into two clear groups of sizes: rocky planets such as Earth and large mini-Neptunes. In essence, his research shows that our galaxy has a strong preference for two types of planets (leaving aside gaseous giants): rocky planets up to 1.75 times the size of Earth and mini-worlds surrounded by gas, which have 2 to 3.5 times the size of the Earth (that is, they are somewhat smaller than Neptune). Our galaxy rarely produces planets with sizes between these two groups.

References

https://en.wikipedia.org/wiki/Exoplanet

https://gizmodo.com/when-will-we-finally-find-a-truly-earth-like-exoplanet-1823067954

https://www.nasa.gov/feature/jpl/new-clues-to-trappist-1-planet-compositions-atmospheres

https://ariel-spacemission.eu/

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