Can M-type red dwarfs have habitable planets?

Artist’s illustration of a young red dwarf stripping away a planet’s atmosphere. Credit: NASA, ESA, and D. Player (STScI) (ScitechDaily.com/Discovery Could Dramatically Speed Up the Search for Extraterrestrial Life)

Young  M-type star erupts very often. And those eruptions can strip the atmosphere off their planets. But otherwise, those small stars are extremely long living. And there is always the possibility that those exoplanets could re-form their atmospheres. The reason for that is when an M-type red dwarf goes more mature. It turns restless. 

But young M-type red dwarfs are very active. And that makes forming life on their planets very hard. Also, the gravitation of a red dwarf is not as powerful as the Sun's gravitation. So if an exoplanet form too far from the M-type star it can just fly away and turn into a rogue planet. 

In this text, the main focus is on the forming of liquid water. That thing is one of the primary elements that make the form of life possible. The primary element in this process is that the temperature on the planet is suitable so that hydrogen and oxygen can burn and form water. 

When the planet is locked, there is the possibility that the heat of the star will blow its atmosphere away. The supermassive exoplanets or super-earth can also have oceans, but there is the possibility that those oceans are so hot that there are no lifeforms. When we are thinking about Gliese 436 B, an exoplanet that has hot ice on its surface. In that case, the planet's gravitation will pull water to ice. In those conditions, the gravitation denies the vaporization of the hot ice. 

There is also the possibility that some massive water worlds have conditions where there is ice on the bottom of the ocean. In that case. Massive gravitation with water pressure makes ice to the ocean's bottom. And if the ocean covers the entire planet. It acts like the gas giant's atmosphere. 

Gas giants' atmosphere rotates at different speeds in each latitude. That thing is visible in image two where you can see Jupiter and its stripes. The windspeed in each latitude is different. 

And that forms stripes in their atmosphere. A similar effect can happen in water planets' oceans if it covers the entire planet. That means there would be sectors where the water speed is different and that causes massive friction. 

And if the deep water layer covers the entire planet, the friction between different water layers will turn that giant ocean into an extremely hot place. And in the case of large super-earths gravitation will keep water liquid even if its temperature is far higher than the vaporization point on earth. 

Image 2 Jupiter is a typical gas giant. 

Those giant oceans are forming clouds and the nightside of the planet is freezing. So those things stabilize the temperature of that planet. But then we must realize that gravitation on that planet must be suitable so that the vaporization of water happens in the absolute right temperatures. That temperature is important for enzymes. Also, if the planet's gravitation is strong, it will pull the atmosphere to flat. Of course, the gas in that atmosphere is extremely thick.

But there is also a super-earth with no atmosphere for some other reasons. In the cases when there are exoplanets without water there are no clouds. And clouds are things that protect the planet's surface from powerful radiation. Also, the atmosphere transports heat to the night side of the locked exoplanets. And the gas layer will stabilize the temperature of the exoplanets. 

If a very young exoplanet goes too close to the M-type dwarf that thing can blow the gas layers from the exoplanet. The M-type dwarf is one of the most typical stars in the Universe. And almost all researchers said, that there could be no lifeforms on those planets. The reason for that is those planets are locked. 

But as we know, many variables affect the forming of the atmosphere. There is a time window when the water can form in the atmosphere of exoplanets. If the planet is too hot the radiation from the star can blow its atmosphere away. 

In the case that the planet is too cold. Water cannot form from oxygen and hydrogen. 

Image 3. Planet Mercury

So researchers think that M dwarf blows the atmosphere away from its planets that are in the habitable zone. So in those cases, the planets share the fate of Mercury. 

Planet Mercury is a very small planet. There is the possibility that Mercury ever had an atmosphere. The radiation pressure that comes from the Sun is higher than red, M-type dwarfs. The sun is a G-type star with a surface temperature of 6000 K. And it's much hotter than M- type red dwarfs. The surface temperature of M-type red dwarfs is 2,400–3,700 K. 

And an M-type dwarf is not anything like the Sun at all. It's far smaller and it's colder than our sun. So the data collected from the Sun should not compare with M-type dwarf stars. 

The solar systems of those stars are small. In the solar or stellar system of the Gliese 581, three confirmed exoplanets would fit inside Mercury's orbital. There is the possibility. That there are Earth-size exoplanets with an atmosphere around the M-type dwarfs. 

https://scitechdaily.com/discovery-could-dramatically-speed-up-search-for-extraterrestrial-life/

https://www.sciencenews.org/article/water-world-extrasolar-planet-loaded-hot-ice

https://en.wikipedia.org/wiki/Gliese_581

Image 1: https://scitechdaily.com/discovery-could-dramatically-speed-up-search-for-extraterrestrial-life/

Image 2: https://en.wikipedia.org/wiki/Jupiter

Image 3: https://en.wikipedia.org/wiki/Mercury_(planet)