#habitable planets

Red Dwarf Habitability

When you look up in the night sky, you can see countless stars, and on a very dark night, you may even see the Milky Way, a cloud like path cut across the sky. 

That alone will tell you our Galaxy is huge, but what you’re seeing is but a tiny fraction of the largest and brightest stars in our Galaxy.

3/4 of all stars are Red Dwarf stars, and yet, with the naked eye, you cannot see a single one of them. Even the closest star to our sun, Proxima Centauri isn’t visible to the naked eye, never mind the others. 

A star like our own Sun is only visible up to around 32 light years away, yet those stars in the Milky Way are up to 20,000 light years away from us. 

So what we see in the night sky is a very poor reflection of what is really out there.

The other interesting thing about red dwarfs is their life span. Leaving aside white dwarfs and neutron stars (both dead star remnants), a star only exists when it’s able to fuse material sufficiently to hold back the weight of gravity upon it caused by its mass. While this material is hydrogen (the main component in stars) the star is said to be in it’s main sequence. Huge blue giant stars tear through that hydrogen stock at a blistering pace, within 100 million years or so, it will have exhausted it and bloated to a red giant, now fusing helium. Smaller but still hot white stars may make it to 1-2 billion years of age before this happens, and even smaller G type stars like our sun, will make it to 10 billion years (we are half way through the main sequence right now). Smaller K and M type stars live much longer, K type stars may live 20-70 billion years and for M types (Red Dwarfs) well .. half a 500 Billion upwards !  Meaning in the life of a Red dwarf, 50 entire lives of G type stars like our Sun will have come and gone.

Why is this important ? Well, how long does a habitable planet take to make ? The honest answer is, we really don’t know, the definition is restricted to the only one we are aware of, and it may turn out to be a outlier or a totally average habitable planet, we just don’t know. 

Even so, planets need time, they need time to coalesce after the star formation, they need time to find a stable orbit and for the lucky ones in the habitable zone where liquid water may exist, they may take time to develop the atmosphere and environment to be considered habitable. So, it would stand to reason, the longer a star lives, the more chance of such circumstances occurring ! 

Except, it’s not that simple. All of the young red dwarf stars we know of (up to 30 million years of age) have one thing in common, massive ultraviolet flares. The HAZMAT program uses Hubble to return constant data on a group of young, intermediate and old red dwarfs, and they found that the youngest stars were producing flares several times a day that we on Earth have seen only a few times since we first began recording it. 

It’s likely that any planet that forms in the habitable zone early on in the stars life, is going to get quite a bath of radiation, and may possibly lose its atmosphere as a result of it, although that isn’t entirely certain, it’s still a big possibility.

However, planets move, they can take a long time to find their final stable orbit, and it’s possible planets can be acquired too over time.