Artist's impression of the new exoplanet in Proxima Centauri. Credit: L. Calçada / ESO

Astronomers Spot New Alien World Orbiting Proxima Centauri

Astronomers have discovered a third exoplanet candidate near the closest star to the Sun, Proxima Centauri. The newly discovered object, designated Proxima d, is twice as massive as Mars and is not in the habitable zone.

The Proxima Centauri system

Proxima Centauri is the closest star to the Sun, which is a low-mass dwarf of the spectral class M. Two exoplanets orbit around it.

The first is Earth-like, located in the habitable zone, and makes a revolution around the star in 11.2 days, and the second is still a candidate for exoplanets and makes one orbit in five years.

Exoplanet one has a mass of at least 1.17 x Earth while receiving 65% of the radiation that the Earth receives from the Sun. Most likely, the planet is subject to tidal capture by its star: on one side – eternal day, and on the other – eternal night. Despite this, according to calculations, it may well have temperatures suitable for life. But Proxima Centauri with a mass of seven Earth is much further from its star, so it is too cold for life.

Astronomers discovered a new exoplanet orbiting Proxima Centauri

A team of astronomers led by João Faria of the Portuguese Institute of Astrophysics and Space Research have announced that they have discovered another exoplanet candidate near Proxima Centauri.

The discovery was made during the analysis of data from the ESPRESSO spectrograph (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), installed on one of the telescopes of the ground-based VLT complex in Chile. The search for the planet was carried out using the method of radial velocities.

The scientists concluded that the collected data can be explained not by stellar activity, but by an exoplanet candidate with a minimum mass of 0.26 ± 0.05 Earth masses (about twice the mass of Mars), which is located at an average distance of 0.029 astronomical units from Proxima Centaurus (less than a tenth of the distance from Mercury to the Sun) and moves in a circular orbit.

Characteristics of the new exoplanet

Given this fact, as well as its proximity to the star, it may have a rather rarefied atmosphere. With a high probability, the planet is devoid of moons (too close to its star) and is also in a state of tidal capture: on one half of the surface, it is always night, on the other, it is always a day.

A year on the exoplanet lasts 5.12 Earth days, it does not fall into the habitable zone, where liquid water can exist on the surface of the planet. Future observations with the UVES, HARPS and ESPRESSO instruments are expected to refine the orbits of all planets and confirm the discovery of Proxima d.

Why is studying this system so difficult?

The peculiarity of the discovery of Proxima Centauri d is that it is an extremely difficult task. Just five years ago, in the winter of 2017, astronomers struggled to the limit to discover Proxima Centauri b, which is three and a half times as massive as the new exoplanet candidate. They did this using the same method of radial velocities – according to the “wiggles” of the star, which it experiences under the influence of gravity of the planet rotating around it.

Such tremors are extremely difficult to register if the planet is low-mass, so new observations are, without exaggeration, record-breaking in terms of sensitivity. This indicates the possibility of searching for exoplanets in other star systems using the radial velocity method.

What makes Proxima Centauri a primary target for observations and exoplanet hunt?

The Proxima Centauri system captures the attention of astronomers not only because of its proximity but also because it is the easiest way to understand whether planets around red dwarfs can be inhabited. Such stars are characterized by strong flares when their luminosity can increase up to ten times for a short time.

Some scientists believe that planets with a thick atmosphere can shield local life from such flares. Others raise the question of whether, under such conditions, essential atmospheres are preserved in principle – and whether they are not completely lost due to flares.

Further observations of Proxima Centauri b and other planets in its system may clarify this issue. It is of great importance because three-quarters of the stars in the universe are red dwarfs. That is, the question of the frequency of life in the Universe as a whole also depends on the potential habitability of such systems.

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Castelvecchi, D. (2022, February 10). Earth-like planet spotted orbiting Sun’s closest star. Nature News.
ESO. (n.d.). New planet detected around star closest to the sun.
Faria, J. P. (n.d.). A candidate short-period sub-Earth orbiting Proxima Centauri?
Starr, M. (n.d.). A new planet has just been discovered orbiting the nearest star to the sun. ScienceAlert.
Wall, M. (2022, February 10). Possible third planet spotted around Proxima Centauri, our Sun’s nearest neighbor Star. Scientific American.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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