Astronomer designs the 'Ultimate Solar System' with an amazing 60 habitable worlds!
Friday, May 30, 2014, 5:47 PM - Our own solar system has just our own planet as its only habitable jewel (at least as far as we currently know). Science fiction like Star Trek, Star Wars, and innumerable others, tend to stick to that same pattern of one life-bearing world per star, with some notable exceptions (like Joss Whedon's Firefly/Serenity universe). So, it's forgivable for anyone contemplating what could be out there in our galaxy to put certain limitations on how many habitable worlds could be orbiting around a star. However, some people, like astronomer Sean Raymond, really go for pushing the limits on this whole idea.
If the name seems familiar, you may remember Sean Raymond as one of the astronomers who discovered Kepler-186f, the first Earth-sized planet astronomers have found orbiting in the habitable zone of its star.
Just a month after the news about this exciting discovery hit the media, Raymond was already working on something much bigger, developing a model for what must be the most habitable star system in the universe.
This project followed up on one of Raymond's previous works, which was to make subtle alterations to our own solar system, to (as he put it in his blog) "make better use of the Solar System’s habitable real estate." In his restructured solar system, there was quite the shakeup in the inner part of the system. Mercury was left in its familiar place, but Venus was kicked out of its orbit, the Earth and Mars had swapped places and were closer to the Sun, and Jupiter was closer in, occupying the outer part of our Sun's habitable zone. Orbiting Jupiter was the dwarf planet Eris (swapped with Io), Europa, Ganymede and an early form of Venus (before it developed its thick, life-stifling atmosphere). In the outer solar system, Uranus and Neptune had switched places and Io occupied the last spot. According to this configuration, the solar system would have the highest potential habitability, based on the composition and atmospheres of the different planets and moons, and their new location around our Sun.
Moving on from there, Raymond started from scratch, designing a star system from the planetary disk up, with the goal of taking this idea of 'maximizing habitable real estate' to the extreme. He started by picking dwarf stars for his planets to orbit, since they are the most stable stars and thus would also have the most stable habitable zones. Then, he packed the habitable zone of one star with sets of binary worlds - two planets that orbit a common gravitational point between them. That kind of thing may seem far-fetched, but there are real examples of this. Pluto and Charon could be classified as a binary world (if there was some kind of official definition for that). Also, using the same principle behind Trojans - minor planets or asteroids that exist in stable orbits, either leading or trailing planets by an angle of 60 degrees - he was able to put two pairs of binary worlds in the same orbit, and he repeated this for five more orbits in the star's habitable zone. That gave a total of 24 different Earth-sized planets!
Moving over to the other red dwarf in this stellar binary pair, he could have just done the same thing with binary pairs and Trojans, but he changed it up a bit. He took the example of Jupiter he had made in his restructuring of our solar system, which was orbited by four roughly Earth-sized moons, and he placed one orbiting in the star's habitable zone. Then, at the Trojan points of this massive gas giant world, at both 60 degrees ahead and 60 degrees behind it, he placed a binary pair of Earth-sized planets, bringing the total number of planet in that orbit of the star to eight. Adding in three more similar combinations in successively more distant orbits (but still inside the habitable zone), brought the total around this star to 36 habitable worlds!
Not quite satisfied with separate systems, he threw these two together, putting these red dwarf stars as a binary pair, orbiting each other far enough away that the systems orbiting each wouldn't destabilize each other. The result was one complete star system, with a total of 60 habitable worlds! Furthermore, since Raymond carefully chose all of the parameters of these planets and their locations around the stars, the entire system is stable. This means that the habitability of these planets will last for billions of years.
This is all, of course, hypothetical, and it's unlikely that such a habitability-rich star system would form.
"I admit that it would be extremely fortuitous for nature to produce a system that was so spectacular," Raymond said, according to New Scientist. "Still, each piece of the system is plausible and even expected from simulations of planetary formation."
So far, the number of planets we've discovered in the habitable zone of their star has been fairly limited. In our own solar system, only Earth and Mars qualify. Orbiting Gliese 667C, a red dwarf around 22 light years away are at least six worlds, three of which are within the star's habitable zone. Studies done on one of our closest neighbour stars, Alpha Centauri B, have shown that it could have as many as 11 planets in its habitable zone, and some of these could be super-Earths, meaning that they could possibly be super-habitable. Only one possible planet has been detected around Alpha Centauri B so far, and if it does exist it's much too close to the star to be habitable. However, this idea that so many worlds with even more potential for habitability than our own world (which is teaming with life) could exist there is amazing.
Ultimately, there may be no habitable worlds around Alpha Centauri B, and there could be no star system anywhere close to being like Sean Raymond's labour of astro-love. However, studies like these, that push the limits to show us exactly what's possible, are the ones that will help us find the 'other Earths' out there, and help us to eventually find other life in the galaxy. As to whether or not that life will be intelligent, advanced and (hopefully) friendly, only time will tell.