M type Stars - Their Hidden Power

Red, Cool, Most Numerous Than Any Other Star Group, but Mostly Overlooked. Yes, we are talking about M-type stars. These stars are being actively researched by scientists; there are several space missions proposed to search for life on their planets. These stars live longer than any other class of stars which is a cool thing. Hi, I'm your friend K* and Today in this post we're gonna discuss M-type stars So Without wasting any time Let's Dive in.

Introduction :

We always start our post with an intro, So M class in the MK System generally consists of Cool Stars that doesn't mean you can walk on its surface. In this group, Stars with 0.45 to 0.8 times more massive than our Sun and 0.7 times larger than The sun in radius and at least 0.08 times Solar luminosity belong to this M class. Temperature is relatively low which is 2400 - 3700 Kelvin So they have cool photospheres but its still enough for melting so many metals like Copper, Iron, Titanium and many other metals. Their Red color comes from low temperatures which is why Hot Stars like O and B types glow in Blue while Cooler Stars emit Mostly around 700 Nanometers which will appear Mix of Red color with an orange hue in human eyes.

Such Stars are usually small in their main sequence, often called Red dwarfs. They Burn their fuel slowly and their fusion is powered by The Proton-Proton Chain or PP Chain, their slow rate of Fuel burning gives them an extremely long time to fuse Hydrogen into helium which can extend up to Trillions of years. One surprising fact is that M Stars never enters in Giant phase due to their insufficient rate of fuel burning and Convective interiors how that happens we'll discuss it in another post in detail of course.

M-type Stars have the most number than any other star group. For example, There are almost 250 Stars from this class in our Local neighborhood within 50 light-years of the solar system But None of them is visible without a telescope. They don't shine enough due to a slower Fusion rate instead mostly they are studied with telescopes. However, there are some extraordinary conditions, such as a very clean night sky, low-level pollution, and a deep, dark sky, where you may be able to see them. You also need very sharp eyesight, as a telescope is often the only way to see them.

However, All the Red Stars are not the same Let's explore them.

Main Sequence or Red Dwarf (V) :

In Astronomy, Hydrogen Fusing stars are called Dwarfs or Main Sequence. these are Hydrogen Fusing Stars that Burn Hydrogen and create a product named Helium. when they produce helium, The convective nature of the core carries it to the cooler parts of the star and dumps it in the outer layers when the appropriate temperature is found this is called convection. Since this kind of Process only exists in low-mass stars but hey! That doesn't mean Convection is the feature of low-mass stars. it works differently with other stars with different masses. In the case of these stars, It never lets accumulates the helium into the center of the star. Therefore, there is no deficiency when they are about to finish hydrogen they Fuse it Easily and Slowly. They live extremely long lives about some trillion years. Yu can check some of Red dwarfs in the image below. We didn't add luminosity because it was in very small numbers.

There are plenty of Red dwarfs in the vicinity of our solar system but none of them is visible due to the factors that we've told you earlier. Many of these stars have planets. Since the M Stars are cool we can live on their planets but we need to find a planet that orbits the Star from very close otherwise it would become an ice world or the Temperature would be too low that humans wouldn't survive. These happens because their small size, Slow Fusion rate and low mass, All these things are intertwined together. such properties a star useless and less interesting for commoners right?

in spite of these qualities, we still have a hope to find a habitable planet where Water can remain in liquid form and it should be stable. By the way, If you want to know what makes a planet habitable for humans there will be a dedicated post. So that we can see it thoroughly.

Subgiant Stars (IV):

As we said earlier Red dwarfs never become giants that's true 100 % True But these sub-giant stars have very little fuel (Hydrogen) left in their core. Since K and M-type Stars spend a very long time in the Main sequence it is impossible to evolve directly from these classes of stars. In such stars, helium accumulates and creates a ball of helium that can't generate energy, it simply can't resist gravity and hence contracts and the outer part of the star expands in response. When Stars contract their temperature gets high while Expansion decreases their heat So they glow in Red color. Since they are somewhat larger than the main sequence phase but smaller than common Giants they are in the transition phase which is called the Subgiant phase. this often happens in the case of up to 8 Solar mass Stars but M type's low mass prevents this entire event. However, Theoretical models suggest that some Massive M Stars can become the Subgiants.

These types of stars are very rare especially in M-class. there are minor reports of findings of such stars. Since our universe is 13.8 billion years old, These stars can live Trillions of years, K type stars usually spend 17 Billion years and G-Type or our Sun-like stars spend around 10 Billion years So they didn't evolve from K and M classes It is unlikely from G types too because G type stars can't cool too soon to glow in Red. There are not enough Stars like this. What do you think let us know in the comment.

Red Giants (III):

You may have probably heard that Our Sun will become a Red giant after 5 Billion Years and This can be its place. Let us remind you the System we are knowing according with called the MK (Morgan-Keenan) System. Which classifies stars on their Mass, Temperature and Luminosity mainly. it doesn't account if a Star was Blue or White in the past, it only looks for the current condition of a Star. If a Red giant will turn White after some thousand years then Scientists will classify it as a White giant.

So, The Stars with 0.8 to 1.6 Solar masses meaning G or F-Type stars when mostly fill helium in the center of their core, can't be used as fuel because those stars don't have the required conditions like you want to pick up 150 Kilograms of weight especially if you are not a heavy weight champion. Therefore, the Fusion rate slows down and gravity contracts the core and outer layers start to expand. Stars in this phase are called Subgiants But the critical point is where the core can't contract anymore. Imagine You want to compress a water pouch without bursting the pouch can you compress it? The molecules of water will exert force on your fingers and you will find it difficult. Something similar happens in the star's core at that time the molecules of the core apply pressure outwards. So Star's outer zone is way too large that it can fit several sun-like stars and the core has its appropriate density now this core can't contract any longer. Welcome to The Red Giant phase. You can see some of these stars.

You can see some of these stars have masses around between 1 to 2 solar masses which shows that Red giants can't evolve from Main sequence M-Stars why? go read the previous sections. 1 or 2 solar masses stars usually start their lives as Yellow or white Main sequence stars and evolve into Red giants, they have reached here by losing temperature. Who knows one day our G-type sun can be seen among Red giants when we will be living on another planet and see our sun back.

Bright Red Giants (II):

These are massive stars with larger volume and Luminosity than a regular giant. However, These stars were not red since birth because you can see in the image below such massive stars never start their lives as red which indicates lower surface temperature instead these stars are in their late period of life. Appearing Red due to various factors. Since they glow in red it means they can also be classified as M stars with larger Mass, Radius and Luminosity but almost the same temperatures.

Red Supergiants (I):

These are the largest stars in the current generation of stars. Stephen - Bolztman law tell us that for stars with the same mass and radius but different temperatures, blue will expand less while red will expand most this is why the Largest known stars are Red Super/hypergiants not the Blue Supergiants. You can see their mind-boggling sizes in the image below. However, Their mass and some other qualities may not be certain but are consistent with current Stellar models. Stars of this type are very difficult to measure accurately we'll discuss it later. Most of the Supergiant stars are variable due to the battle of their Fusion and Gravity. We can discuss it on another post.

Here in this image below, We have selected some of the largest known stars, we often Hear that UY Scuti can fit 5 billion Suns while Stephenson 2-18 can take 2 Such UY scutis. In the image, you can see there are a lot of stars with similar sizes and some become larger or smaller because of their variable nature. It is like you bring 5 Most rich people in the world to your dinner and taking a family photo they won't look as special as the photo with ordinary people. This is how media tell us because we are fond of hearing Largest, Smallest, Longest, shortest or anything with huge properties instead of looking at similar or competitive contestants.

Why is it hard to measure UY Scuti like stars?

Let's talk on this subject why is it so difficult to measure Stars like UY Scuti? First let's understand how modern astronomy works, anyway it's not that modern we've been using the same method for maybe 1000 years to detect distant objects which is to take the help of light only difference is the Modern telescopes with Hi-tech specs. If the light doesn't arrive or interact on our devices the light sources won't be detectable and these Stars are located in many thousands of light years. You can easily imagine There could be many obstacles like dust clouds and fragments of nebulae or Debris disks. these objects can interfere with the light and cause irregularities since our Astronomy depends heavily on Light (Electromagnetic Radiation) and Gravitational waves (in the case of massive objects). Unless we keep an eye on these factors we'll never take accurate measurements.

Moreover, Sometimes Stars and other objects Create veils from outside space. In the GIF image above, you can see the Star is pushing dust, gas and stellar material in enormous amounts. Massive Stars with More than 10 Solar masses create outflow of Dense streams of particles like electrons, protons, neutrinos, dust, gas molecules and other un-discovered particles at tremendous amounts because of their Aggressive fusion and other factors. Dust and gas particles will stop at some AU's or Light years away from the star covering the entire system. The more massive stars can completely disappear inside their own nebula-like cloud blocking around 90 % of their light. Sometimes, If you look at such clouds you can call them nebula but they are not that large. Along with all these, the Star is itself changing size in some days, months or even years. It becomes sometimes smaller or Bigger than the actual size. The Star has become old and gravity is trying to crush it while Fusion in the core prevents gravity from doing so. It was still happening when the star was not even born. At that time Star was almost kept balanced between two forces but now Those two forces are torturing the star, trying to tear it apart or Squeezing it until it becomes a Neutron star or Black hole.

Now let's combine those two paragraph's essences we get a Star that Changes Size, surrounded by dense dust and clouds blurring the Original Star, Located many thousand light years away that Light takes thousands of years to reach our Telescopes or Satellites. Sometimes it may feel that the entire cloud is glowing and dimming. Such photons (particles of light) journey mostly gets eventful and face several challenges like Dust clouds, halos of dark matter, Black holes, Neutron stars or Unseen entities. If a Light from such a Hypergiant were coming towards us but swallowed by a black hole or Absorbed by a huge nebula between us, we'd never see the star through our current technologies.

So Even though we have James Webb and Hubble like Legendary telescopes, these are still not enough for precise measurements. Note, The UY Scuti is not alone Star instead there are thousands of them that are hiding in their clouds or something is making their properties absurd.

Now you know why such stars are very hard to detect.

Cultural Importance:

Since our Ancestors used to sleep in the open night sky they kept many records about Stars that were used to signify various aspects of their lives like Rituals, Marriage, Time to War, Future etc. Some stars from M Class have been important due to their historical and religious Significance. Let's Explore them.

1) Betelgeuse (α Orionis):

It is almost 400 Light years away in the Orion Constellation and This is a very famous star that is known for its violent variable nature, it stands as an Icon for Finding some clues about the Stellar Evolution of Massive Stars But here we're not looking at its astronomical side but at the cultural Star. It is one of the 10 Brightest stars in Earth's night sky so it is common that our ancestors have noticed it. This star can easily be recognized once you know the Stars in the Orion Constellation, especially the 3 Stars. Let's see how the different parts of the world know this star.

• in South African Mythology, this star is depicted as a lion that looks to hunt on 3 Zebras denoted by 3 Stars.

• in Greek mythology, The Orion is sometimes represented by Pelops. this man was cut into pieces to perform a ritual by his father. later on, He was reassembled by The Greek Artisan God Hephaestus. one of the shoulders of Pelops was made of Ivory, it is depicted as Betelgeuse's Mix of Red, orange and white color.

• in Macedonian Culture, Some constellations are perceived as Animals and Tools of Agriculture. They saw The Orion as a Ploughman with oxen. The rise of Betelgeuse around 3 : 00 AM in autumn, Tells the Time to Wake up and go to work in the fields.

• in modern times around WWII, the two Navy ships were named after This Star USS Betelgeuse (AKA - 11) and USS Betelgeuse (AK - 260).

2) Antares (α Scorpii):

This Binary Star is located in Scorpius Constellation at a distance of around 550 Light years. It has also been well-known for centuries in several parts of the world. Let's learn about its significance.

• in Babylonian, This star is known as the Breast of the Scorpion.

• in Mesopotamia, it was known by different names like, The creator of prosperity, The lord of the Seed, The king and many more.

• The ancient Chinese Shang dynasty chose it as the National Star while sometimes it was referred to as the fiery Star because of its Red look. 

Besides those stars, there are several newly discovered stars, including Luyten's Star, Barnard's Star, Garnet's Star, Teegarden's Star, Trappist, Proxima, and many more. These stars are gaining popularity in modern times.

Search for life:

You know that our Earth has taken care of its life for more than 3 Billion years but it won't be the same, due to solar evolution one day Earth will turn into a Burning cemetery. Therefore Scientists are looking for other planets however, Their priority is to search for life evidence in nearby locations, for example, Mars, the Moons of Jupiter and Saturn. But it may not provide support like the Sun because If the Sun disappears Most of the life forms on Earth will extinct, some species can survive in such situations but larger species like Mammals won't survive without it. That's why Scientists are looking for stars with their Exoplanets that can support life As the Sun and Earth. Let's see some of the potential Planets to live.

Proxima b:

This planet orbits Proxima Centauri at a distance of around 7.2 Million Km and is located in the Centaurus constellation around 4.26 light years from us. It is the nearest Star other than the sun hence it becomes Closest Exoplanet. This is basically a super-earth meaning it is many times larger than the Earth and mostly consists of rock and soil. This planet was discovered in August 2016 using Doppler Spectroscopy. When a massive planet orbits a star, it also exerts some force on its parent star causing it to wobble. Therefore The light from the star has some variations not too dissimilar to Pendulum lamps (tiny vibrations) but in very very small amounts our eyes can't detect that. Our Powerful Spectrographs can find these minute variations and find the actual reason for this phenomenon. Our sun also wobbles in its place because of the gravitational effects of Jupiter and other Gas giants.

Proxima b is 1.4 times larger in radius and 1.07 times more Massive Than Earth which means you can fit approx. 3 Earths in The Proxima Centauri b. This planet completes an orbit in just 11.2 days, If you're fond of celebrating birthday parties this planet would be perfect for you because You'll have Birthdays after every 11 days. Studies suggest that Proxima b can be Tidally locked which is a common feature of planets around M type Main sequence Stars in which the planet's one face always looks at the Stars while the other sees the Space. this causes enormous troubles If we are gonna live on such planets based on their composition. Theories and Studies also suggest It's star Proxima Centauri Releases huge flares once in a year which makes it a dangerous place for life. However, If we could live on this planet it could be a great victory for humanity we have a lot of hope on this planet in spite of these issues.

TRAPPIST System:

The TRAPPIST - 1 was discovered in 1999 by John Gizis et.al. It's further observation done by Transiting Planets and Planetesimals Small Telescope (TRAPPIST). It has 7 Known Planets where planets d, e,f and g are worshipped as Habitable candidate planets. Let's take a quick look at the TRAPPIST -1 Planet System.

The Star TRAPPIST - 1 is located in the Aquarius Constellation around 40 Light years away. If we could reach there we would definitely search for planet e which has most of the properties to be habitable for humans. there are a lot of expectations about TRAPPIST 1e. Do you think Can we send a probe there around 40 light-years away because our old technology voyagers have not even crossed 1 light-year after being launched 50 years ago? let us know in the comments.

Kepler - 186f:

This planet is 580 Light years away in the Cygnus Constellation, this planet completes an orbit in just 130 days which is way longer than TRAPPIST - 1 planets and it was discovered by the Transit method. it's mass is about 1.44 Earth Masses, this number misleads us because, at this mass, the planet could be an ocean world or a large rocky planet. According to current understandings, Planets with 1.5 Earth radii are no longer rocky planets they start to become Mini - Gas Giants or Oceanic worlds if This is the case their habitability would be crippled with one solid evidence. The Kepler 186 has 5 known planets and it is the farthest planet from the star, like Neptune in our solar system. Such long distances and lower luminosity of the Star make it harder for Today's telescope king like James Webb, it simply can't study the atmosphere and other entities in this system. There is a Chance of tidal locking because M type Stars have very compact planetary systems you can find several planets in the orbit of the mercury-like planet. This renders planets tidally locked. while it is important sometimes if any planet is too far then it would abandon the system and become a rogue planet.

What if our Sun was an M-type Star?

Let's discuss our last topic in this post. we'll think of two possibilities where first as the sun already enters as an M Star in the main sequence while the second is true and well defined it would become a Red Giant Star someday.

Possibility No.1:

If we think our Earth has been ready after planetary formation then we would be able to see our Star being born because Red Main sequence Stars evolve very slowly but this is only false imagination without a Star and a source of energy life is not possible so Our Solar system would be incomplete and There would be no Earth because it's last planet would reside near the orbit of Venus beyond it planets would be tied loosely probably Escape the Star's gravitational pull. If we even think All the planets are there and our sun turns into a Red dwarf the next minute we'll see large bright flares from our Red sun which would become more powerful than ever, and we will see Gas giants slowly start to leave our system and set out in a never-ending journey of our galaxy. Asteroid and Kuiper belts would disperse in some hundreds of years. Earth-like Inner planets face an eternal Ice age. Plants on the Earth would begin to starve because they won't receive enough radiation to cook their food using photosynthesis, the same will happen to all Photosynthetic Microbes and minor live forms. However, Tough species like Archaebacteria can still survive but the rest of the major groups would suffer badly. Our new sun can't support its system and life on Earth.

Possibility No.2:

It is a well-known Fact After some 5 billion years, The sun would start to expand and in about 10 Billion years become a Red giant. This time Ocean would completely reach the sky covering the whole planet, our Earth's magnetic field would capture this large dense cloud and increase the temperature on the surface, Volcanic eruptions would take place and our Blue Earth would turn into a Lava world. Later on, our sun will again expand and This time it will become enough large to keep Mercury, Venus and Earth inside it maybe Mars can still survive but it would still vaporize due to photo-evaporation. Jupiter and the outer planets would also show Signs of photoevaporation, in which, the long comet-like tail we'll see from far away. It would peel off the gaseous atmosphere of those planets their moons become molten rocks and Icy moons will be disappear due to evaporation.

Sun - in the Future

At this time, If we look back to our sun we will see the same UY scuti-like structures that we've discussed earlier, we will then classify our Sun as The Red Giant star or M III class. Our Sun can't become Supergiant because it doesn't have enough mass. Eventually, Our Sun will keep losing its plasma, creating a large nebula-like structure then finally it will reveal its core which will appear white due to high temperature. This is the Sun's fate. This time the sun would have spent 15 billion years of his life. We need to find another planet before this happens because the Universe doesn't care for our Existence it's our concern we will have to solve it.

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So that's all for this post, See you in another post

Good bye

Have a wonderful day.