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the_fungible_man t1_irv8h4x wrote

The chances are 0.

The nearest star to the Sun, Proxima Centauri, is tiny, with about 12% of the mass of the Sun. The minimum mass for a star to sustain fusion in its core is ~8-9% of a solar mass, so this is a really small, cool, dim red star. And yet, from Earth, this star has a visual magnitude of 11, which is quite bright for a star less than 0.2% as luminous as the Sun.

Proxima Centauri could hardly be any smaller or dimmer and still be a star, and yet it can be easily observed with modest equipment. Any nearer star likewise would have already been detected.

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FluffyTid t1_irve9ba wrote

I was going to say chances are 100 because Alpha Centauri is not the closest star. But your answer is a lot more on point

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[deleted] OP t1_irvujwe wrote

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[deleted] OP t1_irvvk4v wrote

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frenchtoaster t1_irvxkm0 wrote

The question said closest star to Sol, not to Earth. Unless you mean like the person nearest to you is you at distance zero.

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greyl t1_irw30em wrote

No, he's saying the closest star to Sol isn't Alpha Centauri it's Proxima Centauri.

It's pretty confusing though because "Alpha Centauri" is a 3 star system and the individual stars within Alpha Centauri are named Alpha Centauri A, Alpha Centauri B, and Proxima Centauri.

https://en.wikipedia.org/wiki/Alpha_Centauri#Stellar_system

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Aenyn t1_irw4gti wrote

So in a few hundred thousand years it will be Alpha Centauri AB that will be the closest stars to our system?

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skibble t1_irw6r18 wrote

I'm confused. AB are a binary, orbiting their center of mass. Proxima is closest to Sol. How is Proxima gravitationally related to AB? If she were orbiting them, wouldn't she sometimes be closest and sometimes be furthest?

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hilburn t1_irw7atx wrote

Proxima orbits AB with a period of ~550,000 years.

So the "sometimes" is a while, and includes for as long as we've been measuring things

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Oknight t1_irw7odq wrote

The orbital period of Proxima makes it the closest star to Earth for a much longer period than human beings generally care about. Eventually even the Alpha Centauri system including Proxima won't be the closest stars to Earth and the time frame for that isn't all that much larger than a Proxima "year". In less than 3 Proxima years Gliese 710 will pass only 90 Light Days from Sol.

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NavierIsStoked t1_irwg9b5 wrote

>90 light days from Sol

That seems to be well within the Oort Cloud. I would assume that could cause some objects to get directed into to the solar system. Hopefully we will still be around to care.

Reading the wiki about 710, it seems there is an 86% chance of going through the Oort Cloud. I noticed it didn’t say anything about what 710 would be dragging with it. I assume all stars have some kind of Oort Cloud.

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mfb- t1_irvnot8 wrote

Various surveys looked for all objects down to magnitude ~20, that's an equivalent of Proxima Centauri but ~4000 times dimmer, or 250 light years away. Vera Rubin will improve that by more than a factor 100 in brightness.

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echoAwooo t1_irw3nad wrote

The Centauri Solar Cluster has a high visual magnitude because it's a triple system where Proxima is the smallest of the three suns orbiting the barycenter. Proxima contributes very little light to that high visual magnitude, it's all mostly αCenA and αCenB, the other two stars in the system. A and B both together make it the third brightest star in the sky.

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Krail t1_irw90m5 wrote

What are th odds that, say, a brown dwarf could be lurking close, undetected?

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[deleted] OP t1_irvokdr wrote

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qutronix t1_irvq9iu wrote

If there was something with a dyson spehere we would have seen it. They look pretty obvious, a body invisible in visible light, yet shining in infra red.

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[deleted] OP t1_irvvudw wrote

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AndyTheSane t1_irvysht wrote

Where would they put the heat?

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[deleted] OP t1_irw0vli wrote

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mfb- t1_irw4nbr wrote

Computation doesn't destroy the energy. If your system is fed by a Sun-like star you still get a Sun-like excess in radiation. At 6 K or 1/1000 of the Sun's surface temperature you need 1000^4 times the surface area, or a radius of 0.07 light years. The system would show up as an absurdly bright (~20 times the background where we look for 0.001% deviations) and relatively big spot in CMB surveys. You can change the temperature but the result won't change, you can't hide a radiation excess that large close to us. Probably not even 0.001% of it.

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zbbrox t1_irw924b wrote

What if you stored the energy in batteries and physically transported them out of the solar system before the energy was used?

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mfb- t1_irwg4x4 wrote

That would be an exceptionally inefficient approach.

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throwaway1point1 t1_irw3jl0 wrote

I've always wondered about this tho... I have enough knowledge of physics to get really confused, but not enough to understand how exactly it gets there.

There's still always heat, right? Using the energy for computation doesn't mean you're not still retaining the entire energy output of the sun inside a shell. You use the heat... But at the end you still have the heat.

Is it just that theoretically the outer shells are so big that it is simply diffusing the heat of the star across a vastly (vastly) larger area?

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abbersz t1_irw6ljs wrote

>The outermost layers should be at the background temperature and effectively invisible via infrared, unless they occlude something behind them.

This outermost shell would be the least powerful but also the most materially expensive to construct, due to size.

It is incredibly unlikely that a culture would want to absorb 100% of a suns energy using this method, rather than losing a few shells and not having to spend the exponentially increasing cost of new shells. Only way this works is if a species has figured out how to not have to worry about the laws of physics, in which case, why are they bothering with locating it around a specific star in the first place?

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wwarnout t1_irvx0qs wrote

The premise that "The vast majority of ... stars in the Milky Way haven't been directly detected" = "...there are nearer stars that remain undetected" is false. We have not directly detected most stars because most stars are either much, much, much farther away, or are obscured by closer objects/gas clouds/etc.

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Tchockolate t1_irvzvog wrote

Jep. It's like saying because not all tigers are known, one could be in your house. That's not how that works.

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QuiteAffable t1_irw1p6z wrote

Yes, the fact that there is a tiger in your house isn't related to the fact that not all tiger locations are known.

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LevelPegging t1_irveanj wrote

While finding newly undiscovered nearby stars is unlikely, there are wandering stars out there that pass by our solar system and for a brief moment they become the closest star. Scholz's star passed through the Oort cloud around 70,000 years ago, I believe at the time making it the closest star.

About 1.4 million years from now another, larger, star is on a course to pass through the Oort cloud which will cause major disruption and send thousands of comets hurtling into the inner solar system.

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harbourwall t1_irw4u2m wrote

> Scholz's star

Can we tell if it has any satellites, or grabbed any out of the Oort cloud as it passed?

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LevelPegging t1_irw6o3q wrote

I believe its impossible to tell whether it has its own satellites however I imagine it would have picked up something in its gravitational pull. It certainly would have flung a few rocks towards the inner solar system but it would take a million plus years before it reached the inner planets and become detectable.

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Vesurel t1_irv67py wrote

For us to not see it, it would have to be less bright than alpha centauri. It's not like we're searching a 3d space for starts, we're searching the '2d' sky, so it's not like we're going to find out there's a bit of sky we didn't know was there before. So instead we'd find new starts by getting better at detecting fainter and fainter lights in the sky we already know about.

So it's a question of how likely a star within the range of alpha centauri would both meet the requirement for being a star but be fainter in the sky than entire galaxies billions of times further away look to us.

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Small-District8048 t1_irwcypo wrote

I like the way you put that, "... searching the '2d' sky...". But that brings. Question to my mind. If we had another observatory, say Mars or, if needed, one of the outer planets/their moons, is it possible THAT observatory would detect different stars? I mean, the vast majority would be the same, but since the origin of where it was looking from would be different....

Or would said observatory have to be in another system to attain that effect? I realize that even Pluto is a close neighbor when it comes to interstellar distance.

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[deleted] OP t1_irvyaaw wrote

Stars must be above a certain mass to sustain nuclear fusion. If it has less than ~8% the mass of the Sun, it would be a brown dwarf, which only glows faintly from the heat of the initial gravitational collapse. And since we can detect brown dwarfs tens of light-years away, I think we can be 99.9% sure that we've detected all stars closer than that. But there may be brown dwarfs closer than Alpha Centauri that we haven't detected yet.

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[deleted] OP t1_irv8r01 wrote

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[deleted] OP t1_irvfgkf wrote

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[deleted] OP t1_irvknny wrote

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-Proterra- t1_irvw2sb wrote

Depending on your definition of "star".

If it includes only those which sustain hydrogen fusion and have a spectral class of M8 or brighter, I'd say about 10-20% chance that there may be a very dim Red Dwarf hiding somewhere we haven't properly surveyed at 3-4 lightyears or so. Within 2 LY? Not a chance.

If one starts including T- and L-dwarfs, these chances increase, but that's Brown Dwarf territory and muddling the line between planets and stars. There's certainly none within 50 000 AU, but I'd reckon the chances would be slim within 2 LY, especially for L-dwarfs. Finding a T-dwarf at 3 LY? maybe as high as 80%.

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Crizznik t1_irwa559 wrote

As others have noted, the reason there are so many undetected stars in the milky way is because they are dim and very far away, so the light barely reaches us, or they're being occluded by clouds of gas and dust. Close-by stars do not have either of these factors. If they're dim, they're still very visible because they are close (Alpha Centauri and Bernard's Star) and there aren't any big clouds of gas and dust nearby that could be occluding close-by stars.

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Stewart_Games t1_irw8otr wrote

I'd say there is a not insignificant chance, if it is a brown dwarf. Though whether or not you would call a brown dwarf or a "hot Jupiter" a star is up for debate. In fact, two of the nearest brown dwarfs to Earth were only discovered very recently. Luhman 16 , a brown dwarf binary system, was discovered by the WISE mission in 2010. And WISE 0855 , a "sub brown dwarf", was found as recently as 2013.

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TheSavouryRain t1_irw9cbm wrote

Nonzero, but very damn close to 0.

There's a possibility of a very dim red dwarf somewhere near us, but it's incredibly unlikely, except for transient events (wandering stars coming closer than Proxima Centauri).

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[deleted] OP t1_irv8w1e wrote

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