2016 has been a dramatic year – one which may well be looked back upon as a serious society changer in a similar way to 1968.
There is no question at all, however, about what is the biggest story of the year.
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Source: space.com
The discovery of Proxima Centauri b is potentially the most profound astronomical event since 20 July 1969, and perhaps the most profound discovery for four hundred years (since Galileo).
It was only within the last generation that the very existence of planets outside the Solar System was confirmed. With Kepler, thousands have been discovered, although still overwhelmingly planets with are larger than Neptune and close to their star (far closer than any planets in the Solar System are to the Sun, in most instances), and only around the 15% or so of stars which are relatively similar to the Sun. Although it was long considered likely that there were other planets out there, what was most exciting about this is that we can now reasonably infer that almost every star we look at in the night sky has a planetary system. That is exciting – and profound, because it raises the probability of life to very high, and of intelligent life to much higher than we had previously been able to assume.
Every now and then, of course, a planet has been proposed and subsequently confirmed which is within the “habitable zone” (sometimes known as the “Goldilocks zone” – not too cold, not too hot, but just right to support life). Often, further observation has made the crucial existence of an atmosphere to support life less likely. Nevertheless, the important thing is that it captures the public imagination (frankly then making continued funding for this vital research for humanity more politically and socially palatable).
In recent years and months, a much wider range of planets have been discovered, confirming that small planets (like ours) are in fact quite common, even though they were not initially easy to find. Gradually the data are moving to include planets as far away from their star as the Earth is from the Sun, and then further, to give us a much clearer idea of how typical or atypical the Solar System is. Increasingly the odds suggest it is fairly typical – and that is, in itself, very exciting because it cannot be bad for the prospects of finding life (and intelligent life).
Then came 2016. Proxima Centauri is much smaller than our Sun, but is also part of a three-star system, so in fact it was the type of Star initially ignored in the hunt. We now know, significantly, that even such a star can support a planet and, what is more, a planet in the “habitable zone” (that zone is much closer than in our Sun’s case).
The Sun would be visible to the naked eye in the night sky on a planet or moon up to around 80 light years away; although of course there are much larger stars visible to the naked eye on Earth which are much further away than that. However, that roughly 80-year radius seems reasonable because, unlike intergalactic distances and such like, we can easily comprehend it – it makes the average star visible to the naked eye and it means that light reaching us now left those stars within the average healthy/lucky human’s lifespan (for example, light from the sun reaching any alien who can see it with the naked eye left within my father’s lifetime).
Proxima Centauri is just over four light years away – milimetres, in cosmic terms. It is the very closest star to our Solar System; it has a planet around it; and that planet is within the habitable zone. That is stunning – and profound.
It is not profound because there may be intelligent life on that planet. There probably isn’t.
It is not profound because there may well be life of some sort on that planet. If it isn’t intelligent, that confirms life exists somewhere else – which is profound, but actually would confirm something most people (at least, most people who think about it) now assume to be the case anyway.
It is profound because all of us, when we are lucky enough to get a clear night (ideally away from the city lights), look up at the stars in wonder. There is now, for the first time, a reason to go to one of those stars; because we have found one which has a planet absolutely worth visiting. And it is profound because it is possible, within a human lifespan (i.e. when people now living are still alive), that humanity will see images taken directly by a human-made space probe from a habitable planet around another star. We may already know by then that there is life out there, or that probe may be sent to explore whether there is; we may already know by then that the planet could be inhabited, or that it is not but once may have been; we may indeed already know by then that alien civilisations exist, or that they do not within any relevant range of us. Regardless, the very notion of humans already alive seeing directly taken images from the surface of a planet in another system is something which will be looked back upon, just as Galileo is, for centuries.
Ultimately, we humans are not economic units. We are emotional explorers. It’s how we have come to be what we are. And it is how we will be what we come to be. This discovery, therefore, gives us just a hint – quite possibly long after religions, nation states, or even economies have ceased to exist – of what we will come to be. We are truly lucky to be alive to experience it.