how limited are telescopes?

[fab]

Hi
As traveling to other solar systems / visiting other planets seems very unlikely, and given the fact that a space telescope like Hubble has already contributed so much to our knowledge of the universe, I was wondering how limited telescopes were. Could it be possible for example to examine with any precision the surface of exoplanets (with or without an atmosphere) and possibly detect signs of life .. at such a great distance?

Are there any plans for an even greater telescope in the near future?
Thanks!

 

[Beanze]

It's possible. But you would need a whole lot of space to build a telescope large enough. In this case, the bigger - the better. If someone randomly gave me 100 billion dollars, I would invest it all in the biggest telescope ever built. And five times as big as the one currently holding the record!

 

[ramparts]

Detecting signs of life is actually perfectly feasible, and possibly even within the next decade or so. For that you don't really need precision so much as you need to be able to separate out the different wavelengths of light coming from a planet's atmosphere. Civilizations should give off pretty noticeble signatures that you won't get from natural processes.

 

[believer_since_1956]

Telescopes will be diffraction limited. At some point the "roughness" of the lens or mirror no matter how large will limit the detail that can be achieved. Roughness of a mirror limits the ability of a mirror to concentrate the light to a single spot which is what you need to resolve the details. There are techniques such as interferometry which may overcome this in the future.

 

[captdude]

With an admittedly limited application, gravitational lensing can be used to significantly augment the capabilities of any current telescope.

 

[SpaceTas]

a telescope system capable of crudely imaging a nearby earth size planet have already been outlined.
look up Terrestrial Planet Imager.

Of course it is using technology and money we don't have.
YET

 

[kk434]

The TPF was possible to build, but when the funding dried up and it got canceled. But after finding a lot of intresting exo planets it will eventually be necessary to build a telescope like the TPF.

 

[MeteorWayne]

The key word being "eventually"

Look at the chart in your avatar...the tail end of it ain't good

As you said, the money dried up, and it's not in any long range plans for many decades.

 

[raptorborealis]

Detecting signs of life is actually perfectly feasible, and possibly even within the next decade or so. For that you don't really need precision so much as you need to be able to separate out the different wavelengths of light coming from a planet's atmosphere. Civilizations should give off pretty noticeble signatures that you won't get from natural processes.

Good point but possible...to an extent. Those exoplanets would need to be relatively close gallactic wise (which means there would be a billion ETs in the Milky Way and we should see signs of them everywhere). the evidence of Ets is non-existent so it is unlikey they are all that common in the galaxy to be within such detection methods.


but...that word 'eventually' is a wild card.

 

[SpaceTas]

ramparts:
the very difficult part is separating the light of the planet from it's parent star. The planet is so much fainter than the star and right next to the star. Worse than spotting a firefly sitting on the edge of a search light while looking directly at the search light. That's were the super high precision optics come in; the interferometer is used to "cancel out" the light of the star without affecting the brightness of the planet. To see the actual planet you need an 8m + space telescope. We have not developed the interferometers and optics to the precision-level required, and the satellite formation flying technology has a very long way to go in order to achieve the precision required.

There is a neat concept which usings a specially shaped occulter satellite that could be used with the James Webb telescope.
It would be able to spot Jupiter and maybe super earth sized planets round nearby stars if the exo-zodiacal light is faint enough.
(the dust in the system would reflect light, reduceing the contrast of the planet v the sky ... in the solar system this shows up as the zodiacal light. The effect can be seen in the "pale blue dot" image by voyager http://www.centauri-dreams.org/?p=453)

 

[Boris_Badenov]

The largest telescope on the planet is the Keck. It is 10 meters in diameter. In order to see the Apollo sites on The Moon you'd need a telescope 100 meters in diameter. In order to to image the surface of the planets in the Gliese 581 Red Star system 20 light years away you'd need a telescope 100 kilometers in diameter.

 

[Technetium]

Yes, Traveling to other planets are very unlikely.
And we can't send signals to other planets to gather data, due to the extremly large distance we would be waiting possibly thousands of years...

So instead, we gather information from the light that reaches us. If we see it, there's a good stream of light coming from it.
Light is extremly good with detail. So the bigger our telescopes, the more detail we can see.

But for the limit on telescopes.
Telescopes use a huge mirrors to catch the light and reflect it into a lense or screen that we can see with our eyes.
Some Telescopes use multiple mirrors to project into 1 huge image.
So the limit is depending on how big we are willing to engineer these huge mirrors.
Which you just can't estimate.

 

[adrenalynn]

So the limit is depending on how big we are willing to engineer these huge mirrors.
Which you just can't estimate.

You were doing fine until there.

No need to estimate. We can _precisely_ calculate _exactly_ how large.

Welcome to optical physics!