When we analyze all the planets of the solar system we see that there are both inner planets as Outer planets. However, there are different space missions that are dedicated to searching for planets outside the solar system. The planets that are discovered beyond the limits of the zone of our sun are known as exoplanets.
In this article we are going to tell you everything you need to know about the exoplanets and what methods are used to discover them.
What are exoplanets
There are numerous projects attempting to search for exoplanets beyond the solar system. This term refers to planets that are located beyond the solar system, although there is no official definition that meets specific characteristics. More than a decade ago the International Astronomical Union (IAU, in English) has made some distinctions to be able to define the terms of planet and dwarf planet well. When establishing these new definitions Pluto was no longer officially considered a planet and was described as a dwarf planet.
Both concepts refer to celestial bodies that orbit the sun. The common characteristic that encompasses them is that they have enough mass so that their own gravity can overcome the forces of the rigid body so that they can acquire a hydrostatic equilibrium. However, as we have mentioned before, the same does not happen with the definition of exoplanets. There is no consensus to date on characteristics in common with the planets that are discovered beyond the solar system.
For ease of use, it refers to exoplanets as to all planets outside the solar system. That is, also they are known by the name of extrasolar planets. One of them has recently surprised the scientific community, highlighting the importance of understanding what exoplanets are.
Key features
Since a consensus has to be established in order to define, gather and classify these planets, common characteristics need to be established. In this way, the IAU collected three characteristics that exoplanets should have. Let's see what these three characteristics are:
- They will be an object with a true mass below the limiting mass for deuterium nuclear fusion.
- Rotate around a star or stellar remnant.
- Present a mass and / or size greater than that used as a limit for a planet in the solar system.
As expected, comparative characteristics are established between the planets that are outside and inside the solar system. We must look for similar characteristics since all planets usually orbit a central star. In this way, "solar systems" are created simultaneously to generate what we know as the galaxy. If we look in the dictionary of the Spanish royal academy we see that the term exoplanet is not included.
The first exoplanet was discovered more than a quarter of a century ago. And it is that in the year 1992 several astronomers discovered a series of planets that revolve around a star known by the name of Lich. This star is quite special in that it emits radiation at very short irregular intervals.. You could say that this star functioned as if it were a beacon. Thanks to recent research, it has been found new exoplanets which provide further insight into star system formation and its relationship to the search for exoplanets.
Several years after this, two scientific teams discovered the first exoplanet orbiting a star quite similar to the sun. This discovery was quite important for the world of astronomy, since it demonstrated that planets existed beyond the borders of our solar system. Furthermore, it corroborated the existence of planets that could orbit stars similar to our own. In other words, other solar systems may exist, which opens the door to new studies such as those carried out with the Gaia Space Telescope.
Since then, with the improvement in technology, the scientific community has been able to detect thousands of exoplanets in different missions in search of new planets. The best known is the Kepler telescope. In addition, the James Webb telescope has also contributed significantly to this field of study.
Methods to search for exoplanets
Since these exoplanets cannot be discovered physically, there are different techniques to discover those planets that exist beyond the solar system. Let's see what the different methods are:
- Transit method: it is one of the most important techniques today. The goal of this method is to measure the brightness coming from a star. The passage of an exoplanet between the star king and the earth so that the luminosity that reaches us will decrease periodically. We can indirectly infer that there is an extrasolar planet in that region. This methodology has been very successful and is the one that has been used the most in recent years.
- Astrometry: It is one of the branches of astronomy. It is primarily concerned with analyzing the position and proper motion of stars. Thanks to all the studies carried out by astrometry, it is possible to detect exoplanets by measuring a small perturbation that stars exert on the celestial bodies they orbit. However, to date, no exoplanets have been found using astrometry.
- Radial velocity tracking: is a technique that measures the speed at which the star moves in the small orbit generated by the exoplanet's attraction. This star will move toward and away from us until it completes its own orbit. The star's speed can be calculated from the side of the line of sight if we have an observer from Earth. This speed is known as radial velocity. All these small variations in speed cause changes in the observation spectrum of stars. That is, if we track radial velocity, we can detect new exoplanets, which are linked to other research in astronomy.
- Pulsars chronometry: The first exoplanets orbited a pulsar. This pulsar is known as a stellar lighthouse. They emit radiation at short, irregular intervals, like a lighthouse. If an exoplanet orbits a star with these characteristics, the beam of light reaching our planet can be affected. These characteristics can serve as a clue to the existence of a new exoplanet orbiting the pulsar, which has led to new discoveries in this area.
I hope that with this information you can learn more about exoplanets and how they are discovered.