What kind of telescope can see planets in other galaxies?

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I was recently looking at a comic reprinting of Retro Sci Fi Tales # 9, and the synopsis on the site spoke about a story of the "Exposition Universelle", where at a fictitious worlds fair in Paris in 1878, they unveil a "grand inter-galactic telescope so powerful that it can view the surfaces of planets in distant galaxies".

This highly intrigued me as our strongest telescopes, can at best, see blurry images of exostars in only our home galaxy. Now last Sunday, I watched Nova with Neil Degrasse Tyson, and Tyson said that using the sun as a gravitational lens; we could potentially see the surfaces of exoplanets in our home galaxy.

This is amazing but lets take this one step further. Imagine you are an astronomer in say the Star Trek universe Milky Way or the Star Wars galaxy and want to see the surfaces of planets in distant galaxies as intergalactic travel (as opposed to interstellar travel) is still sketchy at best. You would have to see past the intergalactic void which would be quite a long distance even for Star Wars hyperdrives.

What kind of hypothetical method of imaging could possibly be powerful enough to achieve this? Clarketech science is welcome.
 
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  • #2
phinds
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What kind of hypothetical method of imaging could possibly be powerful enough to achieve this?
None. Even with gravitational lensing, there won't be enough light.
 
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  • #3
Vanadium 50
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What kind of telescope can see planets in other galaxies?

Fictional.
 
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Fictional.


Yes I know it’s fictional but this is the sci fi section and I was wondering if someone could help me speculate
 
  • #5
phinds
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Yes I know it’s fictional but this is the sci fi section and I was wondering if someone could help me speculate
Since this can't possibly be hard sci-fic, you get to make up some nifty sounding piece of magic.

"Speculation" is out of the question since that implies that you are speculating about how it could actually be done. It cannot, thus the need for magic.
 
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  • #6
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What kind of hypothetical method of imaging could possibly be powerful enough to ... see the surfaces of planets in distant galaxies
As it was already mentioned the first problem is the amount of light you can capture. If you want to see an object you need to gather enough light (from that object). Just check those monster cameras with wide objectives around any sport event ... Then double the distance and double the diameter of the optics too.

Those spy satellites we are so proud of works from some 100's kilometers with an optics around a few meter.
From the Moon that would mean ~ 4km wide optics, just to get the same amount of light (to have a picture out of that light is a lot more nasty problem).
And the Moon is just right our door.

The closest galaxy is around 70k light years or so. Won't work without magics o0)
 
  • #7
Filip Larsen
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A quick calculation gives me that a diffraction-limited telescope must have a baseline radius of around 200 thousand kilometers in order to resolve visible (green-blue light) from a Jupiter sized planet somewhere in the Andromeda galaxy (at 2.5 Mly). In addition to this you also need some percentage of that baseline covered with actual light collecting sensors in order to build an image. In a sci-fi settings you may, with sufficient hand waving, be able to settle with just two quantum sensors of some kind, but I will leave the calculation of the physical lower limit here as an exercise to someone else.

On top of of the raw sensing capability you also need to address how to suppress noise, how to aim and control aim, and in general how to pull of a ton of technological magic tricks. But if your sci-fi setting is right this may not be a problem for you .
 
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I just finished Isaac Arthur’s Megatelescope episode where he mentions that a highly advanced society could create a “dark matter lens” to warp spacetime to see farther. He did not specifiy if it would allow sight of intergalactic exoplanets, just interstellar. Could it work for intergalactic as well?
 
  • #9
DaveC426913
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The closest galaxy is around 70k light years or so.
🤔

Is that like saying "the closest planet is around 2000 miles or so"? :wink:
 
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DaveC426913
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dark matter lens

Yes, let's use particles that are totally unaffected by the subject we are trying to observe. o0)
 
  • #13
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...double-checked the distances to the Magellanic clouds...
It's like with that confusion with Pluto. Which handful of stars would do as 'galaxy'? As such, the one in Canis Major is even more undecided. So is the 'or so' there :wink:
 
  • #14
Keith_McClary
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20180425_pluto-comparison-bordered.jpg.webp

NASA; picture combined and labeled by S. Hariri
 
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