|This is probably not the answer. Probably. Image courtesy of Andreas Rocha
We are more or less alone.
That's a bit counter intuitive, given that life clearly can arise (hence, y'know, us) and the universe has plenty of the right ingredients and lots of time for it to happen. Just, maybe.... not enough time yet.
|Above: A probe approaches a long lived red dwarf star.
Let's start at the source (link here): The idea comes from Harvard scientists, who point out that our Sun’s lifespan is actually fairly short compared to the lifespan of the most common kind of star in the Universe, red dwarf stars. Red dwarf stars burn for thousands of times longer than our Sun, and do so much more efficiently. To be habitable a world orbiting one would need to be so close to it that its year might only be a few days long, but there’s no such reason such a world couldn’t exist – and it would have a stable environment for longer than the universe has existed so far.
The longer a planet is habitable, the more likely sentient life arising there is – more time, more evolution, more rolls of the dice etc. So habitable worlds around red dwarfs have much more chance of eventually hosting thinking life, just because they’ll live longer – and so sentience might be much more common in the distant future.
This would make our existence, orbiting a fairly hot and short lived yellow dwarf, a bit of freakish accident – hence why we find ourselves (apparently) alone in the sky.
|Above: Earth - just a bit early. Courtesy of NASA
The Harvard team point out that their reasoning might be a bit too simplistic: Life on a red dwarf’s planet would face a lot of challenges….
- Red dwarfs give out hugely powerful X-ray flares
- A planet orbiting close enough to one to be habitable would end up tidally locked – one side facing it’s sun in eternal searing day, the other frozen in endless night.
- Very ancient planets are expected to seize up geologically, like Mars has - which would reduce the planets chances of habitability.
- They can also 'dry out' with all their water becoming locked up as ice.
That brings me back to the rumour floating about that an ‘Earthlike’ planet has been discovered orbiting Proxima Centauri – the closest star to Earth and also a red dwarf. The rumour is that the planet is roughly Earth sized and the right distance from Proxima for liquid water. It’s just a rumour, and, even if it’s true…. Earth sized and the right distance for water aren’t definitive proof of a habitable world: Venus fits that description, and it’s surface is a pressure cooker where it rains acid.
To add some confusion: A group of astronomers called ‘Pale Red Dot’, who have been searching Proxima for planets, have recently submitted a paper, and had it favourably peer reviewed…. but they deny they’re the source of the rumour. The European Southern Observatory, whom the rumour says did make the discovery, have refused to confirm or deny it… read into that what you will. But apparently there will be some sort of announcement at the end of this month.
So…. Saddle up your scepticism and doubt, but pack some wonder along with it - there could be some big announcements in the near future..