First off I haven’t bothered to fact check myself [until after i typed it all up. then i went and found a couple interesting links which I’ve added below] and I did most of this off the top of my head, so feel free to correct me where I’m wrong but don’t expect me to defend any of it unless i happen to be in the mood at the time. The Devils in the details, and all that. In a moment I’m going to ask you to imagine the impossible. I want to first explain why it’s impossible, because if I start with the impossible scenario first, smart alecks would argue the impossibility of the scenario and miss my point entirely. I know this is impossible. I don’t care. I’m saying that up front so you can just ignore the fact this can’t happen. Okay?
Alpha Centauri is the closest star to our own solar system; about four light years away, give or take. This means light traveling from our Sun would get to Alpha Centauri in about four years, give or take. Also, light from there takes about four years, give or take, to get here. When you look up at the night sky, you are not looking at them as they are, but as they were.
For example, our Sun is over eight light minutes from Earth, so if something crazy happened to the Sun, like it blinked out of existence for no reason, we wouldn’t know it for at least eight minutes. When we look at Alpha Centauri, we see what it looked like over four years ago. Since not much seems to happen over there from our perspective, we don’t notice a difference but a lot can be happening that far away and we’d never notice.
Alpha Centauri is actually a three star solar system. So compared to our solitary star Sol, it’s difficult to imagine such a system could be gravitationally stable. However, it must be, because we can observe it is.
Imagine if you can our own solar system with a second star replacing Jupiter (Clarke fans should appreciate that), and a third star out in the kuiper belt where Pluto currently is positioned. Each of these three stars is of a different magnitude and luminosity. Each of these three stars would have significant gravity that would be pulling on each other and anything else that happened to be near them. If Jupiter and Pluto became stars today, their significant increases in gravity would affect our orbit and that of every other body in the system. It would effectively destroy the tenuous balance that has kept our solar system stable for billions of years. Our current orbit would decay. We’d either fall into one of the stars, hit another planet, or fly out into space and become a rogue planet. In any scenario, life on Earthy would rapidly become rather unpleasant.
But what if Jupiter and Pluto had always been stars? What if, billions of years ago, at the inception of our solar system when it was nothing but a swirl of crazy energy and gaseous matter slowly cooling over billions of years into a solar system, what if all the matter and energy that eventually coalesced into what we now see as the asteroid belt currently orbiting mostly in between Mars and Jupiter right now, had instead been absorbed into Jupiter? Jupiter is already a rather large gas giant of a planet, and what is a star really, but a really frikkin big gas giant that’s on fire? If Jupiter had just a little more mass, it probably would have such a massive gravitational energy force upon itself that it would ignite into a star.
What if billions of years ago, the mass that is currently Saturn, Uranus, Neptune, Pluto, Charon, Eris, and all the bits and pieces of what’s currently the Kuiper belt, had instead swirled together into one large entity, big enough to also become a gaseous ball of near everlasting flame? Let’s throw Mercury, Mars, and Venus in there too. That should be more than enough mass to make a third star.
Okay. So now in our mind’s eye, our solar system looks vaguely like Alpha Centauri’s three star system might look, with the addition of an Earth like planet in the mix. Now imagining an Earth like planet at a three star system today seems impossible and in fact it is. However, if an Earth like planet formed at the same time as the three stars, it becomes a little more plausible, doesn’t it? It’s orbit would not necessarily be elliptical like ours is today, but it could perhaps find some stable way to co-exist with the other three stars if it was given a chance to develop as the other entities developed, and if external forces didn’t upset things along the way.
Someone smarter than me would have to do the math, but there are probably several combinations or scenarios where you take three stars and one or more planets and have them coexist if all the objects in space formed at roughly the same time. Are you with me? This is the impossible scenario I mentioned at the beginning of this blog post. It’s a scenario that some scientists have dismissed and ruled out: An Alpha Centauri three star system with one (or more perhaps) habitable planets orbiting around or even between its three stars.
However, other scientists are saying it’s less impossible and perhaps even plausible. I may not be entirely losing my mind, thinking about this.
Now, presumably if there were such a planet near a star system that is only four light years from us, surely we could detect it, right? ..well, not necessarily. The last photograph unmanned space probe Voyager I took happened several years ago now and it could barely see us back then. Voyager is only a few light hours away from us today, but it’s been traveling through and then heading outside our solar system since the 1970s when it was launched by NASA from Earth. As you read these words, Voyager has reached the heliopause and will one day soon officially vacate our solar system officially, literally being the first interstellar man-made object. We are practically invisible to Voyager already, and it’s only light hours away; not four light years.
We can see stars from very far away because stars are a direct light source, but anything that needs to reflect light is practically impossible for us to detect directly outside of our own solar system. There’s been much discussion recently among astronomers and astrophysicists about what’s called “Dark Matter” or “Dark Energy.” When they do the math after making observations of space, the math doesn’t always add up. What we see alone does not account for the numbers. Everything appears to be affected by stuff we can’t see, and scientists call this “dark” matter or energy cuz it doesn’t give off light. It could simply be that there’s so much debris out in space which we can’t directly account for which adds up to this dark matter. Rogue planets for example, or just stuff that at the beginning of time was just really super hot energy like what we think our solar system originally was, but not all energy coalesced into stars and planets. Maybe there’s a lot of stuff out there that is kinda like the asteroid belts we have between Mars and Jupiter, or outside our solar system, but it’s not a belt so much as just.. y’know, floating out there in space. We can’t see it cuz when star light reflects off these things, the light scatters and isn’t strong enough to be seen from here.
Our own moon is the closest natural body to Earth, and we can’t see its dark side. The only reason we see the light side is cuz the sun is shining on it even when it appears to be night here on Earth. If we can’t see the dark side of the moon, and it’s so close, no wonder we can’t see hardly anything else out in space that might be there, aside from stars. So how do astronomers and astrophysicists “see” planets outside our solar system if we can’t see reflections off their surfaces? Well, they look for twinkles and wobbles.
When a star twinkles in the night sky, that sometimes means a non solar body has briefly passed between that star and us. If one studies many of these twinkles over time (perhaps over the course of years or centuries) one can see patters that indicate the size, orbit, and other properties of these bodies. Now, if you measure a star’s “fixed” location in the sky in relation to us, a patient astronomer will determine it’s not fixed at all. Our planet is moving around our star which is itself orbiting around the center of the Milky Way, which is moving towards the nearest galaxy to us, called the Andromeda galaxy, in an ever expanding universe. If you take all these other factors into account and the math still doesn’t add up, that means the star you are observing has a “wobble.” Cuz the star you are observing is also in an expanding universe circling center of the Milky Way, and it might have a planet circling it. That wobble is how the planet we can’t see is affecting that star. if that planet didn’t exist, we wouldn’t get these twinkles and wobbles. So the twinkles and wobbles are proof that something is there, something dark we can’t see, and enough data can help us determine what that unknown something is: like drawing a silhouette of a person based on the shadow they’re casting, w/o being able to see the person casting the shadow.
Say you pick a child up and spin in a circle, holding each other’s hands. The kid is smaller than you so oddsa re she will be orbiting around you as you both spin, but if it’s a big kid who just ate lunch, you will feel that kid’s weight affecting you as well. That’s the wobble. A mathematician could take video of you spinning with the kid and from that video do some computations and calculate how much you weigh and how much the kid weighs. That’s what astrophysicists are doing with the data we find from observing stars. I can’t do it, cuz I suck at math, but that’s what they do. That’s why they get paid the big bucks.
Now presumably, many astronomers have already observed Alpha Centauri’s tri star system and detect no twinkles or wobbles. I don’t know that. I presume that. If you notice, i presume a lot of things. I try not to assume things though cuz that makes an ass out of you and me. I could be wrong, but I’d imagine if scientists detected planets around Alpha Centauri, that would be rather newsworthy and I would have read or heard about it. That’d be news. What if a planet is there but we can’t detect the wobble or twinkle? Back to the spinning a kid analogy again, if one adult spins a kid around, then the wobble is pretty obvious, but if two parents have a kid nestled between them and they’re all spinning around, the weight of the kid is affecting both adults equally. There would be no wobble.
What if the Earth like planet is rotating on its axis between two of the stars, with no orbit to speak of? How’s THAT for impossible?
If there is an Earth-like habitable exoplanet orbiting one or more of the stars that make up the Alpha Centauri system, it could be teeming with life, and we currently have no way of knowing. There is the SETI project which listens to radio waves hoping to find evidence of intelligent life (if we like broadcasting music and news-talk maybe they do too) but reportedly a message was sent back in the 1970s in Alpha Centauri’s direction and the results have been, shall we say, specious at best.