If this turns out to be aliens rather than a low-probability astronomical event, does it imply that getting out into space is a lot harder than it sounds?
There is no infrared excess—that is the weirdest part of the whole thing. It means that there isn’t a large system-spanning amount of material heated by the star and radiating in the infrared, that we are just seeing a small fraction of as it happens to pass in front of the star from our angle. Instead, there must be only a small amount of material that we are seeing a reasonable fraction of each time it occults the star. An infrared excess does not depend on the type of material, merely its surface area.
This and the irregular deep nature of the occultation is very strange—large deep occultations mean the matter has to be diffuse rather than something like a planet, irregularity means theres probably multiple clumps, but the lack of infrared excess means we have to be seeing a pretty good fraction of it. The brightness of the star also wiggles a little bit on timecales of ~20 days for part of the dataset, in a manner they don’t know how to interpret.
The leading theories are:
1 - Dust clumps generated from a giant impact between two planets, spread around the orbital range of that planet. Should be some infrared excess in that case though, and the odds of happening to see that in a system that isn’t actively forming are ridiculously tiny.
2 - Exocomet storm in which large, icy dusty objects rain down practically on top of the star and poof into dust, then zoom back out into the outer system, possibly with one large ancestral object breaking up into multiple ones that share an orbit and pass next to the star at irregular intervals like our own solar system’s Kreutz sungrazers. In this case large amounts of dust would be irregularly generated in close proximity to the star where we are much more likely to see them pass in front. When they went back and looked at the star with other instruments, they found a passing red dwarf star only about 1,000 AUs out which could definitely disturb the far outer system and an Oort cloud equivalent.
3 - Something new, some kind of semi-stable clumpy low mass dust belt or a new form of chaotic variable star. Or the astrometry that ruled out certain classes of explanation being wrong.
As much as I would like for it to be aliens, I think even a 1% belief that it’s aliens is privileging the hypothesis too much. Previous ‘weird’ cosmological objects have all turned out to have far more plausible natural explanations.
All this said, though, it does seem kind of natural for a civilization to put most of its effort into surviving in its own solar system—where energy is plentiful and communication is rapid—rather than spreading outward into tenuous space where the chances of survival are very low. It’s not obvious to me why a civilization should choose to colonize other solar systems. That said, if a civilization chose to do that and was successful in doing that, it would quickly become very populous, but it requires an initial impetus.
But how often does that have to happen? They only looked at about 150,000 stars. There are hundreds of billions in our galaxy alone, and if alien civilization developed even 1% earlier than ours, they’d have had time to colonize the entire Virgo supercluster, so long as they start near the center.
I’d say that at this point we are largely ignorant of the odds of intelligent life existing in a solar system. While at least some basic forms of life ought to be plentiful in the galaxy, the conditions for evolution from simple life to intelligent life (that is, civilization-building life) just aren’t understood to the level that would be required for ANY probability estimate to be given. Note that I’m not saying intelligent life is rare; I’m just saying that both scarcity and abundance of intelligent life are consistent with our current state of knowledge.
But that’s just the prior probability. I can still say that we have strong evidence that the probability of a given solar system having intelligent life is much, much lower than one in 150,000.
I admit that a Dyson sphere seems like an arbitrary place to stop, but I think my basic argument stands either way. If any intelligent life was that common, some of it would spread.
does it imply that getting out into space is a lot harder than it sounds?
It enforces a statement along the lines of “these aliens got space travel recently or getting out into space is a lot harder than it sounds.” That’s weak evidence, at least, for that claim.
But if those are aliens, then aliens must be common. And if aliens are common, then there should have been tons of them that got to the space travel point long enough ago to have reached us by now.
But if those are aliens, then aliens must be common.
Given that the universe started a finite amount of time ago, and supposing there is easy space travel, then there is an interval during which the first colonists have intrastellar space travel but have not visibly done interstellar space travel, and we can estimate how long that interval is. They’re in that interval, or there isn’t easy space travel.
We cannot argue “because there is one, there must have been a previous one,” you can’t do that sort of induction on the natural numbers, eventually you hit one. We can argue it’s unlikely, sure, and we weigh that unlikelihood against the unlikelihood that interstellar travel is hard in order to determine what our posterior ends up being.
They’re in that interval, or there isn’t easy space travel.
But that’s a lot of information. It’s a very short interval. Since it’s so unlikely to be in that interval, this is large evidence against easy space travel.
We can argue it’s unlikely, sure
It’s a probabilistic argument. But what isn’t? There’s no argument that allows infinite certainty. At least, I’m pretty sure there isn’t.
But that’s a lot of information. It’s a very short interval. Since it’s so unlikely to be in that interval, this is large evidence against easy space travel.
I agree that it’s a lot of information. But it’s also the case that we have a lot of information about physics, such that interstellar space travel being difficult is also unlikely. Which unlikelihood is larger? That’s the question we need to ask and answer, not “the left side of the balance is very heavy.”
The general lack of space-going aliens suggests that getting into space is harder than it sounds.
Sure, but we already knew there was a general lack of space-going aliens. Presuming this is aliens, this moves us from “are we the first? Really?” to “are we only shortly after the first? Really?”
Both of those fall under “are we the first? Really?”, or the related hypothesis that we’re shortly after the first. Or did you mean to respond to NancyLebovitz?
Or there are fewer civilizations than we expect, or something is wiping out civilizations once they go to space, or most species for whatever reason decide not to go to space, or we are living in an ancestor simulation which only does a detailed simulation of our solar system. (I agree that all of these are essentially wanting, your interpretation makes the most sense, these examples are listed more for completeness than anything else.)
I probably should have used more exact language. The Fermi Paradox isn’t mostly about species puttering around in their home solar system—it’s about filling a galaxy.
There might be an alien civilization building stuff in its solar system.
If this turns out to be aliens rather than a low-probability astronomical event, does it imply that getting out into space is a lot harder than it sounds?
I’ve read the original paper. http://arxiv.org/pdf/1509.03622v1.pdf
There is no infrared excess—that is the weirdest part of the whole thing. It means that there isn’t a large system-spanning amount of material heated by the star and radiating in the infrared, that we are just seeing a small fraction of as it happens to pass in front of the star from our angle. Instead, there must be only a small amount of material that we are seeing a reasonable fraction of each time it occults the star. An infrared excess does not depend on the type of material, merely its surface area.
This and the irregular deep nature of the occultation is very strange—large deep occultations mean the matter has to be diffuse rather than something like a planet, irregularity means theres probably multiple clumps, but the lack of infrared excess means we have to be seeing a pretty good fraction of it. The brightness of the star also wiggles a little bit on timecales of ~20 days for part of the dataset, in a manner they don’t know how to interpret.
The leading theories are:
1 - Dust clumps generated from a giant impact between two planets, spread around the orbital range of that planet. Should be some infrared excess in that case though, and the odds of happening to see that in a system that isn’t actively forming are ridiculously tiny.
2 - Exocomet storm in which large, icy dusty objects rain down practically on top of the star and poof into dust, then zoom back out into the outer system, possibly with one large ancestral object breaking up into multiple ones that share an orbit and pass next to the star at irregular intervals like our own solar system’s Kreutz sungrazers. In this case large amounts of dust would be irregularly generated in close proximity to the star where we are much more likely to see them pass in front. When they went back and looked at the star with other instruments, they found a passing red dwarf star only about 1,000 AUs out which could definitely disturb the far outer system and an Oort cloud equivalent.
3 - Something new, some kind of semi-stable clumpy low mass dust belt or a new form of chaotic variable star. Or the astrometry that ruled out certain classes of explanation being wrong.
Anyone want to take bets on whether or not this will turn out in ten years to be natural?
As much as I would like for it to be aliens, I think even a 1% belief that it’s aliens is privileging the hypothesis too much. Previous ‘weird’ cosmological objects have all turned out to have far more plausible natural explanations.
All this said, though, it does seem kind of natural for a civilization to put most of its effort into surviving in its own solar system—where energy is plentiful and communication is rapid—rather than spreading outward into tenuous space where the chances of survival are very low. It’s not obvious to me why a civilization should choose to colonize other solar systems. That said, if a civilization chose to do that and was successful in doing that, it would quickly become very populous, but it requires an initial impetus.
But how often does that have to happen? They only looked at about 150,000 stars. There are hundreds of billions in our galaxy alone, and if alien civilization developed even 1% earlier than ours, they’d have had time to colonize the entire Virgo supercluster, so long as they start near the center.
I’d say that at this point we are largely ignorant of the odds of intelligent life existing in a solar system. While at least some basic forms of life ought to be plentiful in the galaxy, the conditions for evolution from simple life to intelligent life (that is, civilization-building life) just aren’t understood to the level that would be required for ANY probability estimate to be given. Note that I’m not saying intelligent life is rare; I’m just saying that both scarcity and abundance of intelligent life are consistent with our current state of knowledge.
But that’s just the prior probability. I can still say that we have strong evidence that the probability of a given solar system having intelligent life is much, much lower than one in 150,000.
Or at least intelligent life that modifies its home system in a way that is visible from thousands of light years away.
I admit that a Dyson sphere seems like an arbitrary place to stop, but I think my basic argument stands either way. If any intelligent life was that common, some of it would spread.
It enforces a statement along the lines of “these aliens got space travel recently or getting out into space is a lot harder than it sounds.” That’s weak evidence, at least, for that claim.
But if those are aliens, then aliens must be common. And if aliens are common, then there should have been tons of them that got to the space travel point long enough ago to have reached us by now.
Given that the universe started a finite amount of time ago, and supposing there is easy space travel, then there is an interval during which the first colonists have intrastellar space travel but have not visibly done interstellar space travel, and we can estimate how long that interval is. They’re in that interval, or there isn’t easy space travel.
We cannot argue “because there is one, there must have been a previous one,” you can’t do that sort of induction on the natural numbers, eventually you hit one. We can argue it’s unlikely, sure, and we weigh that unlikelihood against the unlikelihood that interstellar travel is hard in order to determine what our posterior ends up being.
But that’s a lot of information. It’s a very short interval. Since it’s so unlikely to be in that interval, this is large evidence against easy space travel.
It’s a probabilistic argument. But what isn’t? There’s no argument that allows infinite certainty. At least, I’m pretty sure there isn’t.
I agree that it’s a lot of information. But it’s also the case that we have a lot of information about physics, such that interstellar space travel being difficult is also unlikely. Which unlikelihood is larger? That’s the question we need to ask and answer, not “the left side of the balance is very heavy.”
And that’s why my conclusion is “that wasn’t made by aliens.”
The general lack of space-going aliens suggests that getting into space is harder than it sounds.
Sure, but we already knew there was a general lack of space-going aliens. Presuming this is aliens, this moves us from “are we the first? Really?” to “are we only shortly after the first? Really?”
That’s one explanation, the other being “intelligent life is harder than it sounds” and another being “any life is harder than it sounds”.
Both of those fall under “are we the first? Really?”, or the related hypothesis that we’re shortly after the first. Or did you mean to respond to NancyLebovitz?
Sorry, that was meant to be a response to Nancy Lebovitz.
Or there are fewer civilizations than we expect, or something is wiping out civilizations once they go to space, or most species for whatever reason decide not to go to space, or we are living in an ancestor simulation which only does a detailed simulation of our solar system. (I agree that all of these are essentially wanting, your interpretation makes the most sense, these examples are listed more for completeness than anything else.)
https://www.nasa.gov/feature/jpl/strange-star-likely-swarmed-by-comets
How can they get a mess of objects whirling around a star without getting into space?
I probably should have used more exact language. The Fermi Paradox isn’t mostly about species puttering around in their home solar system—it’s about filling a galaxy.