(ORDO NEWS) — It is more massive than Mars, but noticeably smaller than all other known planets in the stellar neighborhoods of the solar system.
Astronomers working with the European Southern Observatory’s Very Large Telescope in Chile have found a third exoplanet candidate in the Proxima Centauri star system using the radial velocity method.
This is an unusual body from the point of view of exoplanetology, since bodies noticeably larger and more massive than the Earth are usually discovered in other systems.
Proxima Centauri is a red dwarf of the spectral type M5.5, located 4.24 light years from the Sun, that is, it is also the star closest to us. So far, two exoplanet candidates have been known in it – Proxima Centauri b and Proxima Centauri c.
The first has a mass of at least 1.17 Earth, while receiving from its star 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 have now found a third exoplanet candidate in the system, Proxima Centauri d. Its orbit lies almost twice as close to its star as that of the potentially habitable Proxima Centauri b, about four million kilometers, an order of magnitude less than, for example, the distance between Mercury and the Sun.
Therefore, a new celestial object is almost certainly not capable of supporting life in the earthly sense of the word.
The new exoplanet has a mass of about 0.26 Earth. Closest to this indicator in the solar system is Mars (0.107 Earth masses). 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 day.
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.
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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