One of the biggest searches in Astronomy is for Earth 2.0. Earth 2.0 would be an exoplanet with characteristics very similar to ours from composition, atmosphere and even size. However, smaller planets are more complicated to find than larger ones.
This is one of the reasons that the exoplanets found are usually gas giants like Jupiter and Saturn. Exoplanets the size of Earth, or even smaller like Mars, are found at a lower frequency precisely because the techniques are better for larger objects.
The Curiosity rover shows that Mars was probably a river planet like Earth
The space telescope used to search for exoplanets, called TESS, has found 8 Super-Earths. The interesting thing is that six are “key planets” which may explain the lack of planets the size between Earth and Neptune.
Planets that are not in the Solar System are considered exoplanets. They can be found around stars or even alone. Recently, a study even suggested the term blanet of exoplanets around black holes.
The great interest of scientists is the possibility of finding an exoplanet that is similar to Earth. This could indicate an environment that would be conducive to life. Therefore, seeking what is called Earth 2.0 is currently Astronomy’s biggest objective.
The big question in Astronomy
At the end of each decade, astronomers from around the world come together to decide the big question of the next decade. Between 2019 and 2021, several articles were published with this intention called Astro2020.
The consensus among astronomers was that the focus of this decade would be on exoplanets and the search for Earth 2.0. The James Webb Space Telescope itself was launched with this objective, in addition to studying the young Universe. In 2019, the Nobel Prize in Physics went to scientists who found an exoplanet for the first time.
How to find exoplanets?
Planets do not emit their own light the way stars do. Finding them is a complicated mission. The most common way is to call through transient events of exoplanets.
A transient event happens when an exoplanet passes in front of the star it orbits, causing the star’s luminosity to drop slightly for a short period.
Calculating the time the luminosity of the star decreases and the period with which this happens, it is possible to find exoplanets. The disadvantage is that other bodies can cause the same effect as other stars or even the star itself varies its brightness.
TESS is a space telescope that was launched as a successor to Kepler. The idea of TESS is to study these transient events and be able to identify exoplanets in stars neighboring the Sun, that is, stars that are in a nearby region.
TESS has already found 400 exoplanets have been confirmed and more than 6000 await confirmation. Confirmation comes through further observations or statistical methods that may even include the use of machine learning.
Why don’t we find “average” planets?
In the study of exoplanets, there is a problem related to their population. Because it is through transients, Larger planets like Jupiter and Saturn are found more easily. Despite this, planets like Earth and even smaller ones have also been found.
But there is a range of masses in which planets of this type are difficult to find: between 1.5 times the mass of Earth to twice the mass of Earth.
The question remains: why are these planets not found? And if they are not formed with the same frequency, why? That’s why exoplanets between these masses are called “key planets”.
6 Planets Are Keys
TESS identified eight Super-Earths which are exoplanets that have more than the mass of Earth to the mass of Neptune. Six of these objects fall into the range considered key planets. and can help us explain their lack in observations.
One explanation is that key planets may lose their atmospheres through some process and The 6 key planets found by TESS can help us answer this. Simulations of the planets were carried out and one of them showed something unprecedented.
The planet with methane
To understand the atmosphere of these planets and their composition, the researchers who led the work carried out simulations. One of these simulations showed that one of them may present an amount of methane gas that is a biosignature.
It is still too early to confirm whether there is indeed the presence of methane in one of them. The group argues that the The James Webb telescope would be essential to confirm the presence of gas or not in the exoplanet’s atmosphere.