In August 2016, astronomers at the European southern Observatory (ESO) confirmed the discovery of earth-like planets in the Proxima Centauri system – the nearest to our Solar system. In addition, scientists announced that the planet (Proxima b) is located within the so-called habitable zones of stars. Since then, multiple studies have tried to determine how likely habitability of Proxima b.
Unfortunately, most of these studies talked about the disappointing findings. More specifically, most studies tended to believe that the star system is very active and constantly bombards the planet's surface hot streams of cosmic plasma, sterilizing everything on its surface.
However, a team of scientists of the space Agency NASA investigated the different climate scenarios, which could talk about the possibility of the presence of water at Proxima b. The study is called the "Habitable climate scenarios for Proxima b taking into account the dynamic ocean" has recently been published in the scientific journal Astrobiology.
The Work was carried out under the leadership of Anthony D. Del Genio Institute for space studies Goddard. In it took part scientists from the Center of Goddard (GSFC), Columbia University, as well as the company Trinnovim LLC – IT professional providing consulting support to GSFC.
As the researchers note, the planet Proxima b, orbiting the star M class (red dwarf), is continuously being tested. First, it is very close to the star, most likely, has resulted in greenhouse effects on its surface ended at an early stage of its evolution. In addition, the planet is exposed to intense radiation (x-rays and a very powerful ultraviolet radiation) and impact of the stellar wind, which very likely led to the catastrophic loss of a majority of its atmosphere and water reserves, if any.
But at the same time, the researchers note, the evolutionary history of Proxima b is virtually unknown to us, therefore, to exclude the possibility of its habitability would be premature.
"The first and important: we do not know if Proxima b atmosphere; if the atmosphere is still there if it contains water. Without these components, the life that we know is impossible," — said Anthony D. Del Genio.
"Who knows, maybe Proxima b is initially formed without an atmosphere. And possibly atmosphere, but with the lack of water. Maybe it was formed with high-grade and water-rich atmosphere. Very dense atmosphere. The answers to these questions is unknown to us".
"second, Proxima Centauri is a star class M red dwarf. Stars of this type are much smaller and colder than the stars, to the class of which is our Sun (a yellow dwarf), so planets in these systems must be very close to their stars to get enough light and heat to maintain a habitable climate. The problem is that stars of class M are very unstable. They are very active throughout its life cycle".
"third, in the early moments of their evolution the stars are class M — very bright and hot. This may be bad news for the same Proxima b, which because of this could lose all the water still in the early stage of its evolution, more to the point, as it could Harbor life."
The Activity of the stars, especially if we are talking about the system of Proxima Centauri, is important, because even for red dwarfs, it is, according to the researchers, is very high. Only in recent years the star, scientists have noted two very powerful flash. The second was so strong that it was visible to the naked eye. This event questioned the possibility of the existence of life on the planet, because in ordinary circumstances such outbreak would lead to the destruction of its atmosphere and all that is under it.
But a new study indicates that there are many options in which Proxima b still could support life. Moreover, in determining the habitability of those or other ekzoplanet still there is no established konretiki. There are a lot of uncertainties. Therefore, in the case of Proximal b scientists still have a lot of opportunities at least for the assumptions.
According to Del, Genio among these assumptions, for example, there is a possibility that Proxima b formed farther from their star and then for some time slowly migrated to its current location. In this case the planet in its early history were not subjected to severe impact from the side of Proxima Centauri.
Under another scenario on the planet would initially have ten times more water than exists on Earth. In this case, even if Proxima Centauri vaporized 90% of these reserves on the planet was still enough water for the presence of the whole ocean.
Additionally, the planet would initially have a thick hydrogen layer, which would be carried away in the stellar wind, exposing in the end, "living core" of its atmosphere.
"We just don't know how there is the case actually", — says Del Genio.
"Therefore, as the conditional point of reference for future observers, we took a scenario in which the planet has a atmosphere and water, and then, taking into account the specific orbit and distance from the star decided to find out couldwould the presence of the ocean and atmosphere provide the planet's surface conditions (warm enough to support water in liquid form and not too hot to vaporize) that are suitable for habitation".
To test this possibility, Del Genio and his colleagues conducted a series of 3D simulations with permissive orbital and climate of the keys of Earth and extraterrestrial environments using the software dynamics (ROCKE-3D).
As planetary adaptation software for the simulation of the global climate model GISS E2 NASA ROCKE-3D was used to simulate the past and future periods in Earth's history and potentially habitable ancient Venus. Using this software, the team modeled a number of different types of potential atmospheres of Proxima b, which included earth-like atmosphere (with a predominance of nitrogen with a small amount of CO2 to heat the planet) and more Martian atmosphere (net CO2). They also considered whether the atmosphere is thinner or thicker than that of the Earth, its oceans more or less salty (and more deep or more shallow), and if the ocean covers the entire planet.
In addition, scientists have considered the possibility of tidal capture of planets (like mercury) and the presence of orbital resonance of 3:2 (for every 3 turns around its axis, it performs two turns around the star).
"For each configuration, which we introduced, on the basis of an earthly climate model that is currently used to determine the level of warming and increasing greenhouse gases created by man was created a three-dimensional global climate model for Proxima b" — explains Del Genio.
"the Key difference of our study from previous ones is the presence of a dynamic ocean that is the ocean, whose currents lead the heat to colder places. Previous studies of Proxima b used models the "static" of the ocean that is just cool or heat the planet, but not moving."
Del Genio and his colleagues found that all used models give the chance for life on Proxima, and in particular the possibility of preserving water on the planet's surface. In addition, scientists have determined that in the case of tidal capture of planets, heat is transferred from always facing the star side is always turned away from the stars side, which also adds to the chances of survival of life.
"If a planet has an atmosphere and water, Proxima b a good chance to be inhabited", — comments Del Genio.
"We also discovered that ocean currents can transfer heat from the cold daylight side to the night, keeping night part inhabited even if it never sees the light of day. And if ocean planets are very salty, almost all of the planet's surface may be liquid water even in those places where usually the temperature is below freezing".
For those who were upset about the latest news about Proxima b, the news from scientists, NASA must maintain some hope. Moreover, despite the fact that, as mentioned above, earlier observations have shown unpredictability in the behavior of Proxima Centauri, scientists still believe that there are many probabilities in which Proxima b can be inhabited. Are we talking about one of these cases will show future observations.
"unfortunately, on Earth, we do not see the transit of Proxima b. It is difficult to determine its atmosphere, which would answer a lot of questions. However, in the near future astronomers will be able to monitor the heat emitted by Proximal b while moving in its orbit", — says Del Genio.
"Our work shows that astronomers need to be able to distinguish the presence or absence of the atmosphere of the planet, as well as the opportunity to find out – the atmosphere is thin and cold or warm and dense".
According to the researchers, their method of analysis can be applied to other rocky planets orbiting stars of class M (red dwarfs). If you consider that stars such as 70 per cent of their total number in the milky Way, then we should have good chances to find a habitable place, at least in our galaxy.
In the coming years, work will include telescopes and instruments of new generation, which will play an important role in the identification and characterization of exoplanets. Among such tools, for example, include the Space telescope "James Webb" telescope WFIRST (Wide-Field Infrared Survey Telescope) and ground-based instruments like the Extremely large telescope and the Giant Magellan telescope. And you can be sure that one of the first goals of all these tools will be closest to Earth exoplanets.
To Discuss the findings of the research group NASA .
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