Weirdly, the Solar System's star is a yellow dwarf, given that these Sun-like stars are a minority in the Milky Way, with an estimated percentage of less than 10% in the galaxy. The discrepancy is known as the Red Sky Paradox, which scientists have yet to figure out.
Science Alert reports that scientists assume yellow and white dwarf stars are common elsewhere in the universe. However, they are still lacking in numbers as the red dwarf stars (M dwarfs) are the most common type of star. A new study identified a key characteristic of this star that might explain why life like on Earth is rare in the cosmos.
Red Sky Paradox Explained
Despite the efforts to find life on other planets, scientists have yet to detect any signs of life outside Earth. So, where is everybody? Part of the recent disappointment in not detecting life in exoplanets recently discovered is due to the Red Sky Paradox. An article on the website Reasons to Believe listed five enigmatic facts about this paradox.
The first fact is that red dwarf stars are the most numerous in the universe, accounting for 78% of all stars. Second, red dwarf stars burn 20 times longer on average compared to other stars, such as the Sun. Third, red dwarf stars brighten slower than all other nuclear-burning stars during their lifetime.
Fourth, about 59% of all rocky planets discovered so far orbit red dwarf stars. Lastly, about one-third of these rocky planets orbit their host stars at a distance where liquid water could exist on at least small parts of the planet's surface for at least a fraction of the lifetime of their host star.
Assuming that all these rocky planets could host microbial life, it should have evolved into advanced intelligent life and extraterrestrial intelligence would be on a large number of planets. However, given that this has not happened yet despite the abundance of red dwarf stars points to the rarity of Earth's life.
Red Sky Paradox: Scientists Present New Theory on the Rarity of Earth's Life
Characteristic of Red Dwarf Star That May Not Allow Life to Survive
A new paper, titled "Life on Exoplanets In the Habitable Zone of M-Dwarfs?" published in The Astrophysical Journal Letters, discusses how it might be harder for life like on Earth to get started in red dwarf planetary systems because these stars do not have the asteroid and gas giant architecture that promotes life.
A recent report from Science Alert suggests that the results could have implications for the search for life outside the Solar System, especially because most exoplanets that are potentially habitable are found orbiting red dwarf stars.
Previous studies have shown that these stars might not have the most hospitable environment as they tend to be very active, wherein they frequently erupt with flares that would be bad for nearby planets.
Meanwhile, current studies have shown that asteroid and comet bombardment late in the Solar System has contributed to how life existed on Earth as it made the planet more hospitable to life and delivered many of the important chemical ingredients necessary for life. Scientists believe that terraforming and delivering chemicals to Earth will be reduced without the asteroid belt.
Researchers looked at red dwarf systems to know if they could find gas giants, which can gravitationally interact with the asteroid belt. They found that none of the rocky exoplanets orbiting in the habitable zone of a red dwarf star has a known gas giant. However, calculations reveal a population of giant exoplanets orbiting red dwarf stars.
The lack of gas giants in the observed systems suggests they are unlikely to host an asteroid belt, affecting their ability to host life. That may also be one of the reasons why Earth is orbiting a yellow star and not a red dwarf star.
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