A neighborhood full of planets: 59 new worlds in the vicinity of the Solar System

Just a century ago, there was no evidence of its existence.

30 years ago, none had been discovered.

Today, science has already located more than 5,300 exoplanets, worlds that orbit around stars that are not our Sun. Of this extensive list of planets outside our solar system, 59 have been hunted by a telescope located in Calar Alto (Almería). in just five years.

There have been 750 nights of fruitful observation thanks to the Carmenes instrument, which looked only in the nearest solar galactic neighborhood in search of possible tenants.

"If our galaxy were a city, we have searched only in our block of flats, we have not even gone out to explore the neighborhood," explains Ignasi Ribas, first author of the study published today and which compiles five years of work with Carmenes looking for exoplanets. .

After observing 362 nearby cold stars, the so-called red dwarfs, they have been able to establish the most accurate count of the number of planets that accompany them: an average of 1.4 for each star.

Red dwarfs, smaller and fainter than our Sun, are often accompanied by more and smaller planets, such as Earth.

The solar-type ones are around half a planet on average each.

When it comes to imagining those 59 new worlds, Ribas qualifies that not all of them are exoplanets with firm soil and warm temperatures, where Elon Musk could land in his colonizing dreams.

They have only found a handful of Earths and not even all of them are in what is known as the habitable zone.

But four of these rocky, planet-like planets are at an ideal distance from their star;

Not too far to freeze, not too close to burn.

Two of those potentially habitable terrestrial worlds are in the Teegarden star system, 12.5 light-years from humanity.

The other two, recently disclosed by Ribas's team, orbit the star GJ 1002, less than 16 light-years away.

A stone's throw away in astronomical terms.

Artist's recreation of the Teegarden star and its two planets discovered in Calar Alto.

In the background, our solar system. University of Göttingen

The Carmenes apparatus uses a detection method (radial velocity) that does not allow us to know much about the composition of the exoplanets' atmosphere: they only calculate the mass, and also deduce their temperature based on the distance that separates them from the heat of their star. .

"Since we know the mass of the planet, we can know more or less what type of planet it is: rocky type [like Earth], an ice giant similar to Neptune or one similar to Jupiter, a gas giant," lists Ribas.

With these data collected in the period from 2016 to 2020, Carmenes has discovered and confirmed six Jupiter-type planets (with masses more than 50 times that of Earth), 10 Neptunes (from 10 to 50 Earth masses) and 43 Earths and super-

( up to 10 Earth masses).

"That is the fauna that we have found," concludes Ribas, director of the Institute of Space Sciences (IEEC).

The astronomer explains that they have not found more terrestrial-type exoplanets because they are more difficult to locate, being less massive, so it is expected that there will be many more than what they have managed to list up to now.

The system used collects the light from the observed star and measures the small movements of the star caused by the gravitational attraction of the exoplanets that accompany it, which reveals its presence: the more massive, the more noticeable.

Night view of three of the Calar Alto telescopes. Antonio Martín Carillo

"In order to determine the existence of planets around a star, we observe it a minimum of 50 times," explains Juan Carlos Morales, an IEEC researcher at the Institute of Space Sciences (ICE-CSIC).

The instrument was made thinking of studying the systems of this type of cold stars, which had been studied less than other more luminous, large and yellow stars like our Sun. "Since we study cold stars that are intrinsically not very bright, they are very close, so that basically we are doing a census of the solar environment”, sums up Ribas.

In this work, in addition to the IEEC-CSIC directed by Ribas, a hundred experts from more than 30 research centers have participated.

The results are published today in

.

Apart from these listed exoplanets, scientific work has only just begun, because the team has made thousands of high-quality observations that other specialists in the field can use for their own research.

"It is a kind of treasure chest, we have 20,000 high-precision measurements made with Carmenes that we make available to the world scientific community," Ribas points out proudly, data with which they have made the count of exoplanets.

In the commissioning of the instrument, inaugurated in 2015, more than 200 specialists from 11 Spanish and German institutions have participated, such as the Center for Astrobiology, the Institute of Astrophysics of Andalusia, the Institute of Astrophysics of the Canary Islands and the Complutense University of Madrid. on the Spanish side;

and the Max-Planck, the Spanish-German Astronomical Center,

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