In August 2016, astronomers from the European Southern Observatory (ESO) announced the discovery of an exoplanet in the neighboring system of Proxima Centauri. The news was greeted with great excitement as this was the closest rocky planet to our planet, which was also within the habitable zone of its star.
Since then, several studies have been conducted to determine if this planet could actually support life.
Unfortunately, most research has shown that the likelihood of habitability is not good. Between Proxima Centauri's variability and the planet anchored to its star, life would find it hard to survive.
However, a new study conducted by researchers at the Carl Sagan Institute (CSI) has shown how life on Proxima b can stand a chance.
The study, recently published in the Monthly Notices of the Royal Astronomical Society, was conducted by Jack O'malley-James and Lisa Kaltenegger-a research associate and director of the Carl Sagan Institute at Cornell University.
Together, they investigated the level of surface UV flux that planets orbiting M-type (red dwarf) stars would experience and compared it to conditions on the original Earth.
The potential habitability of red dwarf systems has been a topic for scientists for decades. On the one hand, they have a number of qualities that are encouraging, not least the commonality.
Basically, red dwarfs are the most common star type in the Universe, accounting for 85 percent of the stars in the Milky Way alone.
They also have the longest life, with lifetimes that can reach up to trillions of years. Not least, they seem to be the most likely stars to host systems of rocky planets.
This is evidenced by the sheer number of rocky planets discovered in recent years around neighboring red dwarf stars – such as Proxima b, Ross 128b, LHS 1140b, Gliese 667Cc, GJ 536, the seven rocky planets orbiting TRAPPIST-1.
However, red dwarf stars also present a number of disabilities, not least because of their variable and unstable nature. As O & # 39; Malley-James Universe Today stated by email:
"The main obstacle to the habitability of these worlds is the activity of their host stars: regular star flares can plunge these planets into highly biologically harmful radiation, and X-rays are attacked and charged for extended periods of time." The host stars' particle currents threaten the atmospheres of these planets be stripped off over time if a planet can not replenish its atmosphere fast enough. "
For generations scientists have been struggling with questions about the habitability of planets orbiting red dwarf stars.
Unlike our Sun, these low-mass, ultra-cool dwarf stars are variable, unstable, and prone to flare-ups. These torches release a lot of high-energy UV radiation, which, as we know it, is harmful to life and can destroy a planet's atmospheres.
This places significant limitations on the ability of a planet orbiting a red dwarf star to create life or remain habitable for a long time. As previous studies have shown, much of this depends on the density and composition of the planetary atmospheres, not to mention whether the planet has a magnetic field or not.
To find out if life could survive in these conditions, O Malley-James and Kaltenegger thought about what the conditions on earth would be like some 4 billion years ago.
At that time, the Earth's surface was life-threatening, as we know it today. In addition to volcanic activity and a toxic atmosphere, the landscape has been similarly bombarded with UV radiation, much like planets orbiting M-type stars today.
To address this, Kaltenegger and O Malley-James modeled the surface UV environments of four nearby "potentially habitable" exoplanets – Proxima-b, TRAPPIST-1e, Ross-128b, and LHS-1140b – with different atmospheric compositions , These ranged from those similar to today's earth to those with "eroded" or "anoxic" atmospheres – d. H. Those that do not block UV radiation well and have no protective ozone layer.
These models showed that with decreasing atmosphere and decreasing ozone, the higher-energy UV radiation can reach the ground. But when they compared the models about 4 billion years ago with what happened on Earth, the results proved interesting. As O & # 39; Malley-James said:
"The result was not surprising that the surface UV radiation was higher than it is on Earth today, but the interesting result was that even for the planets around the most active stars, the UVs were all lower than Earth. that the young earth supported life, so the reasons for living on planets in M star systems can not be that bad. "
In essence, this means that life on neighboring planets, such as Proxima b, may exist now, even though it is exposed to harsh radiation levels. Looking at the age of Proxima Centauri – 4.853 billion years, which is about 200 million years older than our Sun – can be the reason for potential habitability even more fascinating.
The current scientific consensus is that the first life forms on Earth a billion years after the formation of the planet (3.5 billion years ago) have emerged. Assuming that Proxima b was formed shortly after the birth of Proxima Centauri from a protoplanetary debris disk, life would have had plenty of time not only to emerge, but also to gain a significant foothold.
While this life can only consist of single-celled organisms, it is nevertheless encouraging. Apart from telling us that life outside of our solar system could be quite possible, and on nearby planets, scientists are limited by what kind of biosignatures are detectable in their study. As O & # 39; Malley-James concluded:
"The results of this study argue for a focus on life on Earth a few billion years ago, a world of unicellular microbes – prokaryotes – that lived at high levels of ultraviolet radiation, and this ancient biosphere may have the best overlap with habitable planetary conditions active M-stars, we could provide us with the best clues in our search for life in these star systems. "
As always, the search for life in the cosmos begins with the study of the earth, as it is the only example of a habitable planet. It is therefore important to understand how (under what conditions) life in the Earth's geological history could survive, thrive, and respond to environmental change.
While we may only know one planet that supports life, life has been remarkably diverse and has changed drastically over time.
Watch this video with the latest insights from CSI and Cornell University:
This article was originally published by Universe Today. Read the original article.