Starlight Glimmer wrote:
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This here is also an interesting read. Worlds around F stars would have blue skies, much like ours but more so.
Very interesting indeed!
Starlight Glimmer wrote:
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How long would F7-9 stars last? 5-8 billion years? That sounds like a decent amount of time for life to evolve on a planet around them.
Not so much I think. Even if thermal habitable zones and UV habitable zones overlap for many F-type stars, that doesn't mean that the overlapping region isn't moving while the star evolves. As stated in page 8 of this paper
, the part of the evolution of F-type stars where we should expect stable conditions for our planet is between 2 and 4 billion years at best. Still, plenty of time to have life I suppose but shrink your expectations in that sense.
Also consider that the orbit of the planet should not be placed in some random part of the overlapping region of both habitable zones. Many orbits inside the overlap are going to end outside it in less than a billion years while the regions displace. The best orbit inside the overlap would yield some billions of years of stability as I said, but this orbit is very fine-tuned; for example, for an F-star with 1.5 solar masses the climate stability range is for orbits between 2.535 and 2.566 AU. To have a rocky planet in that very specific region means to hope for fewer possibilities to find habitable F-stars systems.
So, yeah it is possible but we have to keep optimism controlled here.
While writing the last post about O, B, A and F stars habitability prospects I thought something that even if unrelated I would like to share here. Those who know me know that I'm not so convinced life is a common emergence in the universe.
The first argument pointed by everyone (even if it's not he strongest in scientific terms) is an argument from numbers. "In a universe with trillions of galaxies containing hundreds of billions of stars with their planets life has to exist in millions of places at least" Ok, that's fair. We know life can exist (it sounds stupid but it's an important fact that we can take for granted thanks to our own existence) and we know there are around 1025
places in the universe to possibly call home. Wow, a 10.000.000.000.000.000.000.000.000 possible planetary surfaces in the universe. But what usually gets disregarded is the probability of life emerging. It is true that life here on Earth appeared very rapidly and also true that we know for many possible mechanism that would easily form vesicles and self-replicating polymers, meaning that there are possibly few conditions to accomplish to have life, but we still really know very little about the probability of the emergence of life, we still have a habitable planet that formed life just once (as far as we know
) in 5 billion years of history, we still can't recreate the most primitive life-forms in the lab using Earth conditions and despite the possible mechanism hypothesized for early biochemistry we could be experiencing a bias due to the idea that every-day simple chemical reactions were in place (an idea necessary to start the search
) instead of a complex chain of serendipious events that led to a highly improbable situation (which would be for sure more difficult to study and prove). So, we know that there are a lot of possibilities in terms of places for life but we don't really know much about the probability for life in each one of those. What if life is a 1 in 1025
possibility? What if the puny numbers for this probability are as staggering as the planet count in the universe?
Think about lottery. Winning the jackpot in the Mega Millions multi-state lottery in the United States is a 1 in 258.890.850 possibility. If we granted a ticket for every planet in the universe there would be nearly a thousand winners in just our own galaxy. What if we played again? The probability of a planet winning the lottery twice would become 1.5 x 10-17
. Each galaxy would have then a 0.0006% chance to have a planet like this. You would need to search between hundreds of thousands of galaxies to have a reasonable chance of finding a twice-lottery-winning planet. But hey, there would still be 152 million planets like that in the universe. Then, what if we needed a three times winner of the lottery? Well, then the probability for any particular planet would be 6 x 10-26
. Think about that. There would be a 60% chance that there is a single planet in the entire universe with those characteristics. If the probability for life on a planet is at most as winning the lottery three times then we are hopeless, we would probably the only biosphere in the entire cosmos. Now the question is Do you think it is easier to form life than to win lottery three times? Maybe I should realize how difficult in fact it is to win the lottery but for now my intuition (the same at play when one says "look at how large the universe is how can't there be any aliens?") tells me that it shouldn't be as hard as the formation of life, if it was easier why the Earth (that have brought a lot of tickets in comparison to other planets with harsh environments) has only experienced the formation of life once?