How soon will it be until we can see what extra solar planets look like?

Question

How soon will it be until we can see what extra solar planets look like?

Answer 1

Unless our technology of long distant viewing techniques undergo a rapid progress, it won't happen in the lifetime of anyone living today.  We still don't have the optics to resolve most of the stars into "discs" just magnified pinpoints of light.  Even the largest planets are thousands of times smaller than the average star sizes.  The only way we can detect extra solar planet (so far)  is from the way they interact with their star through gravity.

Answer 2

When we send probes, and they send back images,

and the images arrive.

(Absolute Minimum: 2 x distance in light years.)

The wave nature of light prohibits us from ever resolving

enough detail at such distances.

Answer 3

A telescope having a perfectly ground objective mirror, being two kilometers in diameter, would with suitable magnification have a fair chance of resolving the disk of a planet the size of Earth orbiting Alpha Centauri. The planet would be larger than the Dawes limit for that objective mirror. It would have to be built in space, though, since an atmosphere sets its own limits to resolution.

Dawes Limit = 116 arcsec millimeters / (Objective Diameter)

Objective Diameter, in meters, minimum =

(5.624E-7 radians) / Arctan { 2R / d }

where...

R = the planet's radius

d = the planet's distance from Earth

If R = 6378 kilometers and d = 4.3 lightyears, then the objective's minimum diameter is 1793.6 meters.

Answer 4

The major problem is that the light from a star has a "tail" or "halo" and the planet would be in that light tail.  The light of the plant would be less than the light from the star's tail.

The solution is a space based telescope much larger in diameter than the 2.4 meter Hubble telescope.  It might have to be more like 200 meters or more to produce meaningful images of extra solar planets.  There are some new space telescopes in the planning stages.

The Advanced Technology Large-Aperture Space (ATLAS) Telescope is a proposed 8 to 16-meter (320 to 640-inch) optical space telescope that if approved, built, and launched, would be a true replacement and successor for the Hubble Space Telescope (HST); with the ability to observe and photograph astronomical objects in the optical, ultraviolet, and Infrared wavelengths, but with substantially better resolution than the Hubble.

The problem is that very large telescopes >200 meters diameter  would have severe problems with the stable platform for mounting the multi-mirrors such a telescope would need.

One solution might be to build a multi-mirror telescope on an asteroid - using the asteroid as the stable base.  It would be conceivable to make a telescope with a diameter of a mile or more.

Answer 5

in the short term the best prospects are for extrasolar planets that are detected by transit - they pass in front of their star as viewed from earth, and cause the light from the star to dim momentarily. for these planets, astronomers can determine their radius, and given the mass from the standard radial velocity technique, can work out their density. this allows some guesses as to their composition. also the light from the star briefly passes through the planet's atmosphere, allowing spectroscopic determination of the composition of the gases in the atmosphere. this is all a very long way from being able to look at them in as much detail as we can see the planets in this solar system though.