“This graphic compares a Sun-like star with a red dwarf, a typical brown dwarf, an ultra-cool brown dwarf, and a planet like Jupiter. Only about 5% of all stars are like the Sun or more massive; K-type stars represent 15% of all stars, while red dwarfs represent 75-80% (or more) of all stars. Brown dwarfs, although they are failed stars, may be just as common as red dwarfs are, but are even cooler and lower in mass. Red dwarfs remain in fast-rotating, heavily flaring states for up to billions of years dependent on mass, with potential implications for sustaining planetary atmospheres on Earth-sized worlds around them.”(BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
Red dwarfs are the most common stars. They are low temperature and their solar systems are really small. Most red dwarfs might have some kind of planetary systems. And the biggest problem with those long-living stars is their violent eruptions that can blow their planet’s atmosphere to space. This is one version of the thing that introduces the red dwarf’s planets as non-habitable places. Another thing is that. Those planets are locked by tidal forces. And they turn the same side to the stars. So are we right about red dwarfs’ planetary systems? As hostile places. There life impossible?
The first thing is that those small stars are much colder than the Sun. The flares are not as hot as the Sun’s flares. The planet's magnetosphere can blow that incoming plasma away from the planet. Can the planet keep its atmosphere? This depends on the planet’s magnetosphere and the strength of the flares.
The planet must also have an atmosphere to host life. This means that the atmosphere even out the temperature, and the locked planet’s night side can be warmer than astronomers thought. Another thing is that the clouds will decrease the temperature on the dayside. This means that the planets might not be so hostile as we might want to believe.
“Doppler images of a giant starspot on K0 star XX Trianguli.“This picture shows a series of views around the star HD 12545”.(Wikipedia, XX Trianguli).
“This image shows a temperature profile of the evolved star HD 12545 (XX Trianguli), which unlike our Sun, doesn’t just have a small number of tiny sunspots on it, but is dominated by a massive, star-spanning starspot that covers approximately 25% of its surface. Many stars, including low-mass stars, young stars, and rapidly rotating stars, have enormous sunspots that can play a major role in the habitability of their systems: disfavoring them as good candidates for life for now. Over long enough timescales, however, even the lowest-mass red dwarf stars will settle down to a steady, non-varying state of consistent luminosity.” (BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
A simple chart for classifying the main star types using Harvard classification (Wikipedia, Stellar Classification)
The problem is the flares and violent eruptions. The fact about those eruptions is that. The young red dwarfs erupt violently. The eruption periods are transient periods. In the red dwarf's life. Mature red dwarfs are not erupting so violently. And that means that Proxima Centauri is quite a young red dwarf. The flare periods last longer if the star spins fast.
The reason for that is that the centripetal forces drive material to the star's shell. The thing that forms the sunspot. Or the star spot is that star's shell. There forms a lower energy point in the shell of the star. Energy starts to focus on that point. And then that energy flow moves plasma into that point. The thing that can cause the lower energy area, or star spot, is the magnetic pole that pushes plasma away from that point.
"This illustration shows the first Earth-sized planet discovered by JWST: LHS 475 b. Although it’s 99% the size of Earth, transit spectroscopy failed to reveal any hint of an atmosphere, making many worry that the Earth-sized planets JWST is sensitive to have no atmospheres at all. However, even these worlds may someday accumulate their own atmospheres through internal and external processes, especially once the active flaring period of their parent stars has ended." (BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
Or it puts plasma moves faster. That fast-moving plasma can take energy out from that point. The thing. That can make the plasma's lower temperature point. It can also be some kind of particle jet, which acts like a thermal pump. If the low energy point is a large energy point and plasma travels to the middle of it, forming a flare. The difference between a flare and a protuberance is that a protuberance falls back to the star.
The flare requires high enough energy that it can escape the star’s magnetic and gravity fields. The flare can also form if there is an oppositely polar point in the plasma. That means that the electron beam can start to collect ions in an ion plasma. To a certain point. That launches an eruption.
The protuberance follows the star’s magnetic field. And flare travels to the universe. In the large sun- or star spots, there is more plasma that travels in the center of that spot than in the case of small star spots. The eruption ends when the star spot is at the same energy level. With its environment.
"With a strong, planet-wide magnetic field, as shown at right, Earth deflects most of the solar wind away, allowing our atmosphere to persist. Without such a field, Mars loses atmosphere regularly, even during non-flaring periods from our Sun. During flare events, however, Mars loses its atmosphere 20 times faster than during quiet periods. This implies that we may need to wait for planets around red dwarf stars to have their parent stars settle down before atmospheres can be stably maintained." (BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
The sunspot formation. “Although the details of sunspot formation are still a matter of ongoing research, it is widely understood that they are the visible manifestations of magnetic flux tubes in the Sun's convective zone projecting through the photosphere within active regions. Their characteristic darkening occurs due to this strong magnetic field inhibiting convection in the photosphere. As a result, the energy flux from the Sun's interior decreases, and with it, surface temperature, causing the surface area through which the magnetic field passes to look dark against the bright background of photospheric granules.” (Wikipedia, Sunspot)
“Sunspots initially appear in the photosphere as small darkened spots lacking a penumbra. These structures are known as solar pores. Over time, these pores increase in size and move towards one another. When a pore gets large enough, typically around 3,500 km (2,000 mi) in diameter, a penumbra will begin to form.” (Wikipedia, Sunspot)
But we must realize. That sunspots can have different origins. There is a possibility that a massive planet pulls material out from a certain point of the star’s atmosphere. That can cause a hole in the red dwarf’s atmosphere. And then that forms the colder point in the small star’s shell. Or maybe impacting FRB or GRB, Fast radio or gamma impulses can form some kind of star spots. Or some kind of electron beam can form the conditions. Where those giant star spots can form.
“Around the young, fast-rotating M-dwarf stars, the flare rate can be more than a billion (1,000,000,000) times greater than the flare rate for the slowly rotating, more evolved M-dwarf stars. An initially Earth-like atmosphere, around a star such as this at the right distance to have ~300 K temperatures on its surface (e.g., in the right range for liquid water), would be entirely stripped away in only a few millions of years. Even a Venus-like atmosphere, nearly 100 times thicker than Earth’s, wouldn’t make it to even 1 billion years. And this is a true problem for a planet that we’d want to support life on it around a red dwarf star, because we don’t think it can be done without an atmosphere.” (BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
“The TRAPPIST-1 system contains the most terrestrial-like planets of any stellar system presently known, and is shown scaled to temperature equivalents to our own Solar System. These seven known worlds, however, exist around a low-mass, consistently flaring red dwarf star. It’s plausible that exactly none of them have atmospheres any longer, although JWST will have more to say about that in future years.”(BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)In that image, you can see how small a red dwarf planetary system can be.
“TRAPPIST-1 is an ultra-cool red dwarf star with seven known planets. It lies in the constellation Aquarius approximately 40.66 light-years away from Earth, and it has a surface temperature of about 2,566 K (2,290 °C; 4,160 °F). Its radius is slightly larger than Jupiter's and it has a mass of about 9% of the Sun. It is estimated to be 7.6 billion years old, making it older than the Solar System. The discovery of the star was first published in 2000.” (Wikipedia, Trappist-1)
The flare period can last longer than in cases like the Sun. But red dwarfs can exist longer time than the Sun. So, life has more time to advance. Otherwise, there is a possibility that lifeforms can start to form around those stars later than they form around the Sun-type stars. Or it must stay in the oceans. In a very long time.
The red dwarf can be far different than the Sun. There can be only one large sunspot on the red dwarf. That can make those flare eruptions very strong, but otherwise, those planets can be on trajectories where those flares don’t directly hit them. So if we want to search for life. From red dwarfs ’ planets. There are many variables that can cause situations that include unexpected values.
“It’s easy to look at the planets that we’ve found today, see that they don’t have the right conditions to support life, and to assume that they never will, even far into the future. But a combination of internal, eruptive processes — and remember, it takes under one-millionth of an Earth-like planet’s mass to make an Earth-like atmosphere — and external processes like bombardment can lead to the gradual accumulation of an atmosphere could lead to potentially life-supporting conditions arising even many billions of years after a planet has formed. We might not favor life arising around low-mass red dwarf stars anytime soon, but if we dare to be more patient that life on Earth will ever live to see, these overlooked worlds might someday be home to the most common form of life in all the Universe.” (BigThink, Red dwarfs aren’t uninhabitable; we’re just impatient)
https://bigthink.com/starts-with-a-bang/red-dwarfs-uninhabitable/
https://fi.wikipedia.org/wiki/Proxima_Centauri
https://en.wikipedia.org/wiki/Stellar_classification
https://en.wikipedia.org/wiki/TRAPPIST-1
https://en.wikipedia.org/wiki/XX_Trianguli
