Earth is unique beyond all the organisms that crawl all over it. The strangest thing about Earth is our star, Sun. It’s a yellow dwarf.
Sun-like stars are rare in the Milky Way. It is believed that there are approximately 50,000 of them. Below 10 percentG-type stars make up the majority of stars in our galaxy, just like the Sun.
Red dwarfs are among the most abundant stars. They are only half the mass as the Sun and have the longest lives of all stars.
These light-weights can be used for up to 75 percentAll the stars in the Milky Way. Statistically, one would think that life would emerge on a planet orbiting a red dwarf if it did.
We are still here, with our yellow Sun. This contradiction between reality and expectation is known as the Red Sky ParadoxScientists are still trying to find the answer.
Accepted into The Astrophysical Journal LettersAnd Upload to the preprint server arXivIt is still in process peer reviewpublication could provide a clue.
Basically, it seems like it might be much harder for life as we know it to get started in red dwarf planetary systems – because they lack the asteroidgas giant architecture to transport the necessary ingredients to life on Earth-like worlds.
The results could have implications on our search for life in the Solar System beyond Earth, particularly since exoplanets considered “potentially inhabitable” are often located in orbit around red-dwarf stars.
The most promising targets in our search of habitable planets are red dwarfs in certain respects. Red dwarfs burn hydrogen fuel more slowly because they are smaller than Sun-like star.
They can hang around for potentially trillions of years – much longer than the estimated 10 billion-year lifespan of the Sun and even the 13.8 billion-year age of the Universe. This means that life can emerge and possibly thrive for longer periods of time.
Our current detection techniques also have the potential to detect red dwarfs. They burn slower than the Sun, so they are cooler and dimmer. This means that the habitable zone – the distance range from the star in which habitable temperatures can be found – is much closer. Astronomers have recently found an exoplanet in a habitable zone near a red dwarf star. An orbit lasting 8.4 days.
It seems that life’s existence and emergence might be difficult.
Previous studiesSome scientists have suggested that red dwarfs may not be the most welcoming environment. Red dwarfs are active and can often erupt with flares that could lash nearby planets with radiation.
The authors of the new paper – astronomers Anna Childs, Rebecca Martin, and Mario Livio of the University of Nevada, Las Vegas – wanted to determine if red dwarf systems had enough of the ingredients that we think kick-started life on Earth.
Current studiesEvidence suggests that the asteroid- and comet bombardment of Earth’s crust late in the Solar System’s life span altered it in ways that made it more suitable for life and gave it many of its chemical ingredients.
The chances of life being terraformed and provided with chemical delivery systems are greatly reduced without an asteroid belt.
Modelling suggests that for a stable asteroid belt to form, and late asteroid bombardment to occur, a gas giant must be present beyond the distance from the star called the snow line. Beyond this, volatile compounds can condense into solidice. This is because such an enormous gas giant can gravitationally interact the asteroid Belt, causing instabilities which pelt asteroids toward the habitable zone.
The researchers then looked at red dwarf systems in order to find one of these gas titans.
48 red dwarf star systems have confirmed, rock exoplanets that orbit in the habitable zones. 27 of these have more than one exoplanet. 16 of those have mass measurements that can be used to locate exoplanets.
A gas giant is a planet with a mass between 0.3 to 60 times that of Earth. JupiterAfter calculating the snow line position for these systems, the team began to search for gas giants.
They discovered that no system with an Earth-like, rocky planet was found in the habitable zone.
According to statistical calculations, there are a number of giant exoplanets orbiting red-dwarf stars beyond the snowline. This implies that red dwarf stars could theoretically have asteroid belts.
The fact that there are no known red dwarf systems that have habitable zone rocks worlds is a sign that the Red Dwarf planetary system architecture could be very different to the Solar System we love.
There are many assumptions. One example is that asteroid impact may not be as important. Perhaps life on red dwarf exoplanets isn’t as similar to Earth. Perhaps we underestimate the importance of the habitable area.
Based on current knowledge and understandings of life, however, red dwarf planets are not in good shape.
“The absence of giant planets in (so far) observed systems containing exoplanets from the habitable zone suggests that these systems don’t harbor an asteroid belt or the mechanism necessary for late-stage delivery to the habitable area.” The researchers write.
“It is therefore unlikely that any observed planets in the habitable zones harbor life if asteroid impact are necessary for life.
This could explain why our planet doesn’t orbit one of these red-eyed stars.
The research has been accepted into The Astrophysical Journal LettersAvailable on arXiv.
