@Asbo Zaprudder I'm seing different values than those (like the ones in the linked chart) but I concede i am no expert.
en.wikipedia.org
How many M-Class planets do you think there are?
- Thread starter C Johnson
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Yes, different sources give different estimates. There doesn't appear to be a consensus. There is perhaps 50% uncertainty in the population percentages and the total number of stars in the Milky Way might be as low as 50 billion or as great as 400 billion. It's hard to tell because the solar system is embedded inside it. Being within a factor of two of the actual values would be an achievement. That between 75 and 80% are class M red dwarfs isn't in doubt - even given their lower luminosity.@Asbo Zaprudder I'm seing different values than those (like the ones in the linked chart) but I concede i am no expert.
File:Stellar Classification Chart.png - Wikipedia
Oh I understand. Parsing the sources is also important. After all, you'll get different numbers if you consider all stars vs just main sequence stars.
Neither of us are quoting the latest peer-reviewed scientific literature. I haven't had access to that for decades. Wikipedia is not a primary source. I was using http://www.atlasoftheuniverse.com/startype.html, specifically this graphic:
90% of stars are on the main sequence so the numbers shouldn't be very different. I was surprised how much variation there is in various estimates I did find, given the size of the potential sample size. Your figures are similar to the ones that I remember from years ago.
If the power law of number with respect to mass continued into brown dwarfs and planetary bodies - either bound or unbound to parent stars - we should expect vastly more of those objects than even red dwarfs.
The salient term for stellar mass distribution is initial mass function. The estimates of this vary quite a bit below 0.5 solar masses - dim stars being harder to observe. A different power law might also apply,
Source: By JohannesBuchner - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44779435
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At least Wikipedia does list their sources—and whenever possible, I do try to source those.
As near as I can tell, the data in the chart I linked to comes from The Real Starry Sky (Journal of the Royal Astronomical Society of Canada, Vol. 95, p.32)
Assuming 100 billion stars, 8 percent would be 8 billion.
90 percent of that assumed value gives an 8 percent value of 7.2 billion.
A difference of 800 million stars is not chump change IMO.
Anyway, whatever the percentages, the more main sequence stars you can include as viable, the better the chances for an Earth analog.
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An aside: Thanks for the trip down Memory Lane. I haven't been to that site in years.
You are assuming that the 90% fraction applies equally across all spectral classes. Still, as you say, it makes little difference. The Wikipedia data might well be the most current estimate. It ties in better with the numbers I had in my mind initially, but searching around threw up a few different values and I went with the lowest estimate. In any case, the human race is probably not going to visit any planets around any other star in our lifetimes and perhaps only using Von Neumann or Bracewell type probes within the next millennium, so it really is a bit of an academic exercise.
Need to distinguish between visiting a planet, and colonization. Incompatible biochemistries was a issue that I first came across in the science fiction of Poul Anderson.
I suspect that Earth like planets are rare in general. I suspect that planets with biochemistries that are compatible are extremely rare.
I suspect that Earth like planets are rare in general. I suspect that planets with biochemistries that are compatible are extremely rare.
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Planets or moons capable of supporting life are probably numerous. It wouldn't be surprising to find life elsewhere in our own solar system. Advanced life would most likely have to be planets that have an ecosphere that has been stable for a few billion years at a minimum. It took about 3.5 billion years for earth to develop primitive multicellular life. In the shooting gallery of space I would guess that would be rare. My own opinion is that life is probably everywhere, but advanced multicellular life is very incredibly rare, and advanced technological life even rarer.
What about habitable planets that have an abundance of the things we need but only plants various other flora evolved and no form of animal life whether vertebrate or invertebrate?
What if there is an abundance of that kind of situation?
What if there is an abundance of that kind of situation?
There could be as many as many as 300 million potentially habitable planets in the Milky Way galaxy, according to research published in The Astronomical Journal. This is based on data from the Kepler space telescope and other research, which suggests that a significant percentage of Sun-like stars could host rocky planets within their habitable zones.
300 million is quite the number for our galaxy alone, but that doesn't mean they harbour life.
Additionally, we tend to look for carbon based life (not consider potentially life that could evolve that's NOT carbon based)... but even so, the possibility was proposed that there might be about 36 actively communicating civilisations in the galaxy.
In Star Trek, the Borg encountered 10026 species by the time VOY Dark Frontier happened... so that might be a TAD on the high end...
I think I read in some studies that it has been proposed that the potential number of intelligent civilisations in the Milky Way could be about 10,000.
300 million is quite the number for our galaxy alone, but that doesn't mean they harbour life.
Additionally, we tend to look for carbon based life (not consider potentially life that could evolve that's NOT carbon based)... but even so, the possibility was proposed that there might be about 36 actively communicating civilisations in the galaxy.
In Star Trek, the Borg encountered 10026 species by the time VOY Dark Frontier happened... so that might be a TAD on the high end...
I think I read in some studies that it has been proposed that the potential number of intelligent civilisations in the Milky Way could be about 10,000.
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Weeeeeeeeell that's only the ones that have not managed to off themselves or go extinct by their own hand or tentacles, or other appendages /s
Actually on a more serious note I do wonder how other species adapted that maybe didn't have hands similar to ours but did have to rely on different limbs. How would they interact with their world and such would be so fascinating to figure out. Maybe some computer modeling
There's so many complicated variables with this.
Even assuming that the atmosphere is one that can support human life, what of the gravity, what of predators, what of diseases? I mean sure, we might land on a planet and be able to breathe, but there's so many other factors that would prevent us from surviving. If we're looking at class-M planets as worlds humanity can thrive on, we're probably not talking many at all, at least not without modifications to the biosphere.
Even assuming that the atmosphere is one that can support human life, what of the gravity, what of predators, what of diseases? I mean sure, we might land on a planet and be able to breathe, but there's so many other factors that would prevent us from surviving. If we're looking at class-M planets as worlds humanity can thrive on, we're probably not talking many at all, at least not without modifications to the biosphere.
You know what I'm more surprised at, how many "Rogue Planets" there is estimated to be within our Galaxy.
Talk about a good place to hide stuff for "Story Line" purposes, "Rogue Planets" should be harder to find and if there are as many as listed, it would be hunting for needles in a hay stack since they are naturally harder to observe since they aren't around a Star System.
Let's not forget about Rogue Black Holes & InterStellar Rogue Black Holes.
Also Rogue Stars AKA InterGalactic Stars.
Talk about a good place to hide stuff for "Story Line" purposes, "Rogue Planets" should be harder to find and if there are as many as listed, it would be hunting for needles in a hay stack since they are naturally harder to observe since they aren't around a Star System.
Let's not forget about Rogue Black Holes & InterStellar Rogue Black Holes.
Also Rogue Stars AKA InterGalactic Stars.
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Not to mention all these interstellar comets.
3I/Atlas path through the solar system as depicted not include any asteroids or probes in its path.
It is supposed to get near Mars…second close call with a comet.
Now, one way we can send something to the Moon are little puffs like Beresheet.
Might a Mars orbiter also be able to do that?
We have until October—and Mars gravity is weaker than ours.
I asked the Gemini AI, but it gets a lot wrong.
3I/Atlas path through the solar system as depicted not include any asteroids or probes in its path.
It is supposed to get near Mars…second close call with a comet.
Now, one way we can send something to the Moon are little puffs like Beresheet.
Might a Mars orbiter also be able to do that?
We have until October—and Mars gravity is weaker than ours.
I asked the Gemini AI, but it gets a lot wrong.
To have any type of advanced multicellular life you have to have a planet that's hosted a somewhat stable ecosphere for at least a few billion years. Earth took about 4 billion years to get to that point.
Which does mean if it happened once, it can happen again. I'm just not optimistic about a large number of planets hosting advanced multicellular life.
Which does mean if it happened once, it can happen again. I'm just not optimistic about a large number of planets hosting advanced multicellular life.
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