Trappist-1
Perhaps most strikingly different from our system is the Trappist-1 system, 39.5 lightyears from here, in which the star itself is entirely different to our own.
Trappist-1 is a red dwarf star not much bigger than Jupiter, around which seven rocky planets have been discovered, and they were profound discoveries at the time in 2015. 7 planets around a star is a new record and is a testament to the advancement of skills in planetary sciences.
This could be a potential zone for life, but we first need to understand the conditions the planets are trapped in:
Tidal Locking
All or most of the planets around Trappist-1 are tidally locked which means one face of the planet is always facing the star, in the same way that the moon is tidally locked to earth – we never see the far side.
How does it work?
In order to be tidally locked, you have to be orbiting close enough to the larger (or equal) body of mass. Once our moon was close enough to Earth, the gravity of Earth caused the moon to bulge out (due to a difference in gravity between the near and far side of the moon), and creates a torque counter to the moon’s rotation, slowing it down until it locks in place.
Just like the moon, these exoplanets are tidally locked because they are close enough to their star that gravity has the same effect.
Can they host life?
That depends. This is where it gets complicated. If a planet was tidally locked to our Sun, it would be scorched like burnt toast like Mercury, and Mercury isn’t even that close. In fact, the most distant of Trappist-1’s planet, Trappist-1h, is six times closer to its sun than Mercury is to ours. They would be molten af!
However, the Sun is not the most common type of sun out there. That title goes to Red Dwarfs like Trappist-1. These stars are supercool and dim, and account for over 70% of all stars in the Universe. None of which we can see with the naked eye.
Trappist-1’s luminosity is merely 0.05% of our Sun, which means it is less likely to completely strip its planets to the bone, and could even create conditions for life. But naturally, it’s a lot more complicated than that.
For a start, the planet’s time orbiting the sun could be crucial. If they have been there over half a billion years or so, the sun’s heavy radiation could have had plenty of time to ionize their atmospheres to oblivion. Research suggests that the system is not that old, but there’s so much more to consider:
Complications
Tidal locking means that one side of the planet is perpetually day and still really hot, and the other side is eternally night and really cold. But physics makes this planet a much less welcome place than that. If any of these planets have a decent atmosphere, a number of thermal conditions could create extremely high speed winds that would create planet-wide hurricanes circling the globe at thousands of miles per hour. Although imagining standing in these winds is not too pleasant, they do have a plus side.
The hot winds on the front facing side would transport that heat over to the dark side, providing some energy and perhaps even melting the ice that may be found there. This, combined with some gravitational stretching of the ice could create large oceans of water either beneath the ice itself or closer towards the central band which is neither facing toward or away from the Star; A Twilight Band.
Perpetual glaciers could feed a ring around the earth with water, which could realistically expand the band to be much larger than you might think at first. In fact, a more accurate name for these planets has been given; Eyeball Earth. A planet in which the ‘pupil’ would be scorched desert, the ‘iris’ could be a front-facing zone cooled by the icy water, and the ‘white’ of the eye could cover the rest of the planet, increasing in thickness the further back you go.
Can we live there?
As far as exoplanets go, Eyeball Earths are probably one of the better types, but it would take some getting used to.
We would be confined to the band around the earth where the sun is forever at a low angle, giving us an eternal dusk, the only daylight coming for those adventurers who might want to explore the completely inhospitable desert at the sub-stellar point – where the star is directly overhead. Always.
On earth, most life depends heavily on the circadian rhythm from the rotation of the earth, so if there was native life, it would function in an entirely different way, perhaps migrating back and forth when appropriate, and we would have to adjust accordingly, too.
The perpetual super-hurricanes might force us to either go underground or to find a mountainous location with a valley that might break up storms.
In fact, if the planet in question is particularly mountainous with high friction, like that of Earth or more this would actually help prevent these winds and also improve the air-conditioning effect of heating cold winds from the night side in the day side.
Conclusion
So, the bad news is that it’s going to be a rough time adjusting to this incredibly threatening planet for colonial humans, and who knows how it may cause the colony to evolve.
The good news is that life around Trappist-1 will have Trillions of years to work it out before the low-energy star they depend on dies out. Indeed, red dwarfs may be some of the last surviving objects in the Universe along with Black Holes.
The best news is that, assume we ever got a clear day, the view outside would be beyond even the most imaginative sci-fi artists. Each planet’s orbital period ranges from 1.5 days to 15 days, meaning if we were stations on one of them, not only would we be able to observe giant bodies of mass several times the size of our moon moving across the sky at speed, but we would be able to planet-hop from one to the other with comparative ease.
Image source:
Orbit Comparison
Tidal Locking
Eyeball Earth
Trappist Tourism