Physics discussion: FTL drives, Speed of Light, Life in the Universe, etc

[Vertigo]

Um... what about stars passing close enough to each to be able to transfer life's building blocks from one system to another? We had a recent example of Scholz's star that passed within 0.82 light years of the Solar System 70,000 years ago. See Scholz's star - Wikipedia

Fascinating I was completely unaware of that! Thanks!

However:

Comets perturbed from the Oort cloud would require roughly 2 million years to get to the inner Solar System.[2] At closest approach the system would have had an apparent magnitude of about 11.4.[4] A star is expected to pass through the Oort Cloud every 100,000 years or so

That would suggest the life would still be subjected 2 million years of exposure to deep space and associated radiation damage before it reached the inner system. Also life would have had to reach that far out in the 'donating' system in the first place in order for the exchange to take place. But still interesting all the same!

 

[Danny McG]

What a quote....

"We had a recent example of Scholz's star that passed within 0.82 light years of the Solar System 70,000 years ago"

Only 70,000 years ago eh? That IS recent

 

[Serendipity]

Fascinating I was completely unaware of that! Thanks!

However:

That would suggest the life would still be subjected 2 million years of exposure to deep space and associated radiation damage before it reached the inner system. Also life would have had to reach that far out in the 'donating' system in the first place in order for the exchange to take place. But still interesting all the same!

Scholz's star came in as far as 52,000 astronomical units from the Sun - which equates to the inner edge of the Oort cloud. Apparently we should by laws of probability expect a star to come INSIDE the Oort cloud once every 9 million years, i.e. much closer than Scholz's star. So the potential for transferral of life would very much increase under these circumstances...

However, these numbers do beg some very interesting questions in themselves - like can there be a hidden very small dark star locked into orbit around our Sun or did life as we know it start in another star system from us?

 

[Venusian Broon]

Fascinating I was completely unaware of that! Thanks!

However:

That would suggest the life would still be subjected 2 million years of exposure to deep space and associated radiation damage before it reached the inner system. Also life would have had to reach that far out in the 'donating' system in the first place in order for the exchange to take place. But still interesting all the same!

I thought this too, but actually being embedded in ice is about the best possible protection from cosmic rays - even better than heavier elements. As it stands cosmic rays can penetrate up to about 3km into the Earths crust (although I don't know if that is because the most energetic rays finally get snuffed out at that level or that's as deep as we can mine at the moment!)

I see calculations that a water shield of one metre is enough to reduce radiation to terrestrial background levels - although I can't vouch that is true.

Hence 'dirty snowballs' or really big chunks of Oort/Kupier belt objects are the ideal transport - also given that extremophile life would also likely have a very slow metabolic rate in frozen conditions. Nice for the long journey times - although if they are not just frozen solid and just packaged, they will need some form of energy, however small to just eek by.

However this does not explain how they got there in the first place - could these ice objects be common 'nurseries' that always have the conditions for very simple life to appear (so that they are absolutely everywhere?)

If this was the case then spreading into inner systems and rocky worlds is then quite easy - not only are all these objects subject to all sorts of gravitational disturbances with bigger objects knocking them about all over the place, but big events such as supernova's could really push huge amounts all over the place.

 

[Vertigo]

Well not quite 'much closer' Scholz's star came to 52,000AU and we can expect as close as that or closer once every 9 million years. The Oort cloud is believed to range from around 50,000AU 100,000-200,000AU. But that is very theoretical we can't detect bodies of that size that far out so it is only what we currently believe the Oort cloud to look like. So Scholz's star was already at the inner edge of the cloud. I think a body massive enough to be a star out there would have been detected; the limit of the Sun's gravitational effect before the galactic gravitation takes precedence is what defines the limit of the Oort cloud. However something like Planet 10 is another matter (which neatly brings us back to the original thread!).

All in all I agree life could have started in another star system but here I must apply Occam's Razor. Which is the more likely; that it evolved here or out there? Sure it is probably just as likely to evolve on another star as on Earth but I think the transfer is far far less likely. Which, of course, is not to say it's either impossible or didn't happen. But you must always keep in mind that life is just as likely to have evolved here as it is to have evolved in any close passing star system. So why is there so often so much resistance to the idea that it did so and this search for a frankly less likely solution?

As you say @Venusian Broon, life has to have managed to get into the other star system's Oort cloud/Kuiper belt first. And I'd venture to suggest that it's probably a lot harder to get out that far than to have come in from that far. Again, though, not impossible just less likely.