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I know everyday we are discovering new things, but is there any limit to what we can find about what happens in space. I saw on the news that we had found a new planet, approximately how long or how much research does it actually take to get this kind of information, is their any limit to our knowledge about the planets that we come up with?
Question Date: 2004-04-05
Answer 1:

This is one of the most interesting questions I have ever been asked on Scienceline.

The short answer on the discovery of the "new" planet is that technology drives a big part of discovery. One needs to photograph a piece of the sky night after night and remove all the KNOWN objects to help find the new ones.

Because objects in the solar system are much closer than objects further away, they will tend to move a lot relative to the distant "fixed" stars....the main limitation is on the brightness.

The amount of sun light reflected is a function of the SIZE of the object (its diameter, say) and its REFLECTIVITY or albedo... that is what fraction of the sun light impinging on it is actually REFLECTED back to us. So a small object at great distance simply does not show up using the best we have ... say the Hubble telescope. There is a threshold below which even the Hubble cannot "see" a small low albedo object.

The other factor is the patience of the observer. One has to look at LOTS of data to find a dim small distant object and that takes a lot of effort and time. As the technology advances (better detection limits, ability to remove spurious effects, etc), then we can push the detection limit downwards... But we will NEVER be able to see from Earth say a 100 meter sized object at the distance of say Pluto... its just so dim that it can not be seen.

The detection limits ARE being pushed down because there are dedicated teams of astronomers and experts in optics that are interested to work on this issue.

Answer 2:

We can only know what we can observe in the time that we have. Theoretically, our time is infinite, but in practice that probably isn't the case. In any event, we certainly can't know *everything* there is to know about the universe, since to know all that would require having a model of the entire universe, down to every last photon - in short, we would need to be the universe itself.

How long did it take to see this planet? That depends. We can't image planets now with even our most powerful telescopes. However, we can see the stars that they orbit, and we can measure the effects of the planet's gravity on its star, if the planet is big enough. How long does that take? At least an orbital period, and some of these planets have orbital periods of days, others of many years. We have not seen any planets with orbital periods of decades around other stars,but the reason for that is that we probably haven't been watching for long enough.

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