They discover the second exoplanet closest to Earth

The exoplanet triples the size of the Earth and depends on a star almost twice as old as the Sun

Source: RTVE
It is not ruled out that there are more planets in the system that orbits Barnard
An international team, led by Spanish scientists, has discovered a planet outside the Solar System (exoplanet), the second closest to Earth, which triples its size, and orbits around the star Barnard, a red dwarf that doubles age almost of the sun.
The work, published by the journal Nature, is the result of an international collaboration led by Ignasi Ribas, of the Institute of Space Studies of Catalonia (IEEC-CSIC), with the participation of scientists from the Center for Astrobiology (CAB), of the institutes of Astrophysics in Andalusia and the Canary Islands, the Calar Alto Observatory, the Complutense University of Madrid and the CSIC.

It has carried out one of the largest international observation campaigns in history, in which telescopes around the world have taken about 800 measurements, «a huge amount of information collected for more than 20 years», explained Ribas in statements to Efe.

«All these data have allowed us to characterize the planetary system that orbits Barnard», the second system closest to us and in which, moreover, «we do not rule out that there may be more planets,» says the researcher.

But, how is this system? The newly discovered planet depends on the star Barnard, a red dwarf of between 7,000 and 10,000 million years, «almost twice as old as the Sun», relatively inactive and the fastest of the night sky.

«A frozen world»
Barnard b, baptized in honor of his hostess, takes about 233 days to orbit his star and, although it is relatively close to it (at 40% distance from Tierra del Sol), it is a cold world and dark that could be around 170 degrees Celsius negative.

«It’s an icy world because it receives very little energy from its star: only 2% of what the Earth gets from the Sun», and it is located near the so-called ‘ice line’, an orbital zone around a star in the that volatile compounds like water can condense in solid ice. Therefore, it is «very unlikely» that Barnard b has liquid water on the surface, but it can not be ruled out that it has it in the subsoil, explains Ribas.

In addition, compared with Proxima b, which is considered the planet with the best chance of harboring life outside the Solar System, it seems unlikely that this super-earth could contain any form of life, but «life sometimes finds skillful ways of surviving» , cautions the Catalan physicist.

The finding has been possible thanks to the Doppler technique, one of the many methods designed by astronomers to discover planets impossible to observe directly. A technique that looks for planets from the effects it causes on its star because, when a planet orbits a star, the gravitational pull causes the star to move as well.

«And according to physics, when a light source approaches the observer, its spectrum shifts slightly towards the blue and its wavelength is shorter and, when it moves away, it moves to red, towards longer wavelengths. Therefore, when we see a star that wobbles (approaches and moves away), it can be deduced that there is a planet in orbit, «Ribas points out.

Measurements of telescopes from around the world
The finding of the exoplanet, which is part of the Red Dots and CARMENES projects dedicated to search for planets near the Solar System, has been possible thanks to the high precision measurements of telescopes from around the world.

Among them, the famous planet hunter HARPS and UVES spectrograph, both of the European Southern Observatory (ESO). HARPS, as explained by Guillem Anglada Escudé, of Queen Mary University in London, has played «a vital role in this project».

«The combination of instruments was key to being able to corroborate our results», emphasizes the Spanish astronomer who, in addition, led the discovery of Proxima b a couple of years ago.

And, HARPS, which measures changes in the speed of a star caused by an exoplanet that orbits it, is capable of detecting speed variations of even 3.5 km / h (a rate similar to the one we use when walking).

The work has used observations of seven different instruments that during 20 years have taken 771 measures, a «huge» amount of information, Ribas emphasizes.

«The discovery represents a significant advance in the search for exoplanets around our stellar neighbors, with the hope of finally finding one that has the right conditions to house life,» concludes IAA researcher and co-author of the paper, Cristina Rodríguez- López.

In the work they have collaborated in the study of scientists from Chile, China, France, Germany, Israel, Poland, Switzerland, the United States and the United Kingdom.