Our cosmic neighbourhood might actually very busy.
Have you ever looked up at the night sky and wondered what is out there? We have all pondered the big question, are we alone? Well, we may finally have an answer. Astronomers have taken recent data and calculated that we have 36 neighbours in the Milky Way, suggesting that we are far from being alone!
So how did they come up with that figure? And what does this mean for our quest to find aliens? Will we be able to meet them just like Star Trek?
Sadly, these astronomers didn’t look up into the night sky, see 36 different civilisations waving at us and call it a day. Instead, they used a brilliant equation called the Drake Equation (albeit a modified version) to estimate how many Communicating Extra-Terrestrial Intelligence (CETI) are currently alive.
In the past, the Drake equation has given us mixed results. We just don’t have enough data, so we had to estimate. This meant we got a result of anywhere between 0 and 15,600,000 CETIs in the Milky Way. Not a very useful result at all!
This is because the Drake equation tries to calculate the number of habitable planets and how many can produce CETIs. We simply don’t have enough data for such an equation to be accurate.
Instead, these astronomers took a new route that involves the age of Stars.
Our Star System is 5 billion years old, and we know that life got going fairly early and has evolved at a steady pace since then. In other words, it is doubtful that an advanced civilisation could have evolved much earlier or later in a Star’s life. This means the age of a Star that could host intelligent life must be around 5 billion years old.
Using observed Earth-like exoplanets of Stars that old, they can extrapolate out and estimate how many exoplanets in the Milky Way could host CETIs. This route cuts out a lot of the guesswork and gives us a much more accurate picture than the previous Drake equation.
But, we still don’t know how likely life is to start on such an exoplanet, how likely it is to develop into a CETI or, for that matter, how long CETI civilisations last! Remember we did nearly send the world into nuclear armageddon not that long ago…
Being the clever clogs these guys are, they went about figuring out what the likely hood of these chances are, also known as Copernican Astrobiological Limit (CAL). Rather than guessing these changes like before, they looked at everything from elements needed to support such a civilisation to how stable an exoplanet’s orbit is. After a lot of work, they settled on a worst-case scenario, the most likely and the best-case scenario.
The worst-case scenario suggests there are only 8 CETI’s whilst the best case suggests 2,900! However, the study concluded that 36 is the most likely number of CETIs currently active in the Milky Way. This sounds great! Even in the worst-case scenario, there are aliens out there waiting to be contacted.
But, these are just estimates, do they actually have any real use other than speculation? Yes, because these figures show that we have only started to scratch the surface when it comes to searching for CETI’s.
SETI (Search For Extra-Terrestrial Intelligence) has been combing the skies since 1984, looking for the signals such a civilisation would create. We have come close, notable potential events are the Wow! signal and BLC1. But as of yet the galaxy seems dead and void of life…
After decades of search, SETI seems to be screaming that we are alone. The silence of space is deafening and the existential crisis of those at SETI seems guaranteed as they search from Star to Star only to find nothing.
However, this study shows the SETI shouldn’t give up too soon. Also, someone should check up on their astronomers and make sure they haven’t driven themselves mad yet.
With 36 CETIs in the Milky Way, on average they should be 17,000 light-years away from us. This means that their signals will be so weak that our current technology won’t be able to pick them up! What’s more, the data suggest they are far more likely to live around a low mass M-dwarf star, which are really hard to spot over that sort of distance!
So not only would we not be able to see their signal, we might not actually be able to see their host Star. It looks like SETI is searching for an invisible needle in a gigantic haystack. Even worse, it would take at least 34,000 years to get a two-way communication to confirm that these truly are advanced aliens!
This is all the more worrying when you realise that the astronomers estimated that CETI’s only last 100–1000 years. Both our civilisation will have crumbled to dust before we can even hope to get a reply to the cosmic call.
This may sound not very optimistic, but humanity is proving that an advanced civilisations have the capability to wipe themselves out. Whether it is nuclear weapons or the huge environmental toll on the planet they inhabit, advanced civilisations seem to be doomed from the offset. Our humanity’s future is not absolute and long term climate change is a real threat to our species’ survival. Advanced aliens will also have these challenges to overcome, meaning CETIs might only be a brief flash of intelligent brilliance before they inevitably wipe themselves out.
That right, we (and all the other alien civilisations) might be too clever for our own good.
But what about the best-case scenario? Surely with that number of advance aliens, we can contact one of them?
Well with 2,900 CETIs, on average, they should be 1,880 light-years away. This is close enough for us to see the dwarf star they most likely inhabit, but their signals still might be too weak at that distance. Even if we could see their signal, it would take about 700 years to find them at SETI’s current rate. It takes time to observe Stars and there are an awful lot of them at this distance or closer. But, even once we finally find them, it will take 3,760 years to verify with a two-way communication. So we still can’t communicate properly, and the aliens will be long gone by the time they get our reply.
So even with a Galaxy packed full of thousands of advanced alien civilisations, the distances between us is still too great for us to ever communicate.
Is there really 36 alien civilisations in the Galaxy? Does that mean we aren’t alone?
Right now, 36 is by far our best estimate. But this research shows that at the very least there should be some intelligent life in our Galaxy, despite the fact we haven’t found any yet. We have only observed such a small portion of our Galaxy, there is a lot of places these aliens could be hiding. Concluding that we are alone because we haven’t found aliens yet is like proclaiming that there are no sharks in the world because there are non in your bath.
But, this also shows just how mind-bendingly vast our Galaxy is, we will be waiting thousands of years to find and communicate with our alien neighbours even if there are thousands of them. Our cosmic neighbourhood could be pack to the brim, but the enormous distances will always keep us alone and isolated on this little wet rock we call Earth.
It seems we truly live on a cosmic desert island.