Question About Observing The Cosmos

My question is simple, and probably has a simple answer. I have read that some scientists theorize there is a tenth planet beyond the edge of our Solar system, perhaps out by the OORT Cloud. The question is: Why hasn't anyone seen it? What I mean is, we have telescopes that reach far into space; we behold distant galaxies...so why couldn't they see a close planet, if it existed?

Please, I know the tenth planet is a far-out hypothesis; I'm not asking whether you think it exists or not. It just seems if it did, scientists would have seen it by now, since they're able to peer so far out into space.

I hope you get the meaning of what I am asking, lol.

They have seen it. And a couple others, too. However, as there is still debate as to whether or not Pluto is a planet, these remain for the most part unclassified.

There are several threads in this forum discussing this.

Originally posted by daboga75 My question is . . I have read some scientists theorize there is a tenth planet beyond the edge of our Solar system, perhaps out by the Oort Cloud. The question is: Why hasn't anyone seen it? I'm not asking whether you think it exists or not. It just seems if it did, scientists would have seen it by now, since they're able to peer so far out into space. I hope you get the meaning of what I am asking, lol.

You are right, Daboga, astronomers can see great distances into space which is also a look back in time. The accepted age for the universe, i.e., post Big Bang time, is 13.4 billion years.

ASIDE: Around 1650, Anglican Archbishop James Uusher (sometimes Usher) of Armagh, Ireland, calculated the very moment of creation - and by extrapolation, the age of the universe - was October 23, 4004 BC. This date was widely accepted in Christendom. It was referred to in the famous Scopes Trial held in Dayton, TN, in 1925. (On July 21, the jury deliberated just 9 minutes to find John Scopes guilty). Religion offered certainty.

RESUME. The dating - age - of the universe is based on the red shift (Doppler effect) observed in quasars - quasi-stellar radio sources - which are believed to have formed shortly after the Big Bang. NOTE: “Big Bang” is a derisive misnomer coined by Sir Fred Hoyle who opposed the theory at first, but which has stuck. Astronomers prefer to think in terms of a Great or Rapid Expansion and not an explosion.

In 1909, astronomers Lowell and Pickering predicted the existence of an unseen planet, “Planet X” for unknown and not ten, based on perturbations in Neptune’s orbit. After an intensive search by astronomers around the world, Clyde Tombaugh discovered Pluto on February 18, 1930. 1915 photos taken by Lowell in his search were found to have included Pluto, but it passed unnoticed.

MOD EDIT:Fixing italics.

[edit on 3/6/2006 by cmdrkeenkid]

The problem is that once you get out to that far reaches, you can consider planetoids to be "Dark Matter". We can see far away galaxies because the galaxies, for the most part, give off TONS of light. However, planets like Pluto, the earth, and all planets actually, DON'T give off light, but instead reflect it.

This means that for us to see it, we have to have a close enough light source to it to reflect light off it. The smaller something is, the less light is reflecting off of it, the harder it is to see. Also, as you get further and further away from a light source, fewer and fewer photons per area are hitting it. After it reflects, then it also depends how far away WE are from that object, and how many photons reflect off of our mirrors into pictures.

In the end, you're left with VERY few photons per area for nonluminous objects. So much so that other stars lightyears away will overpower the light that's being reflected - and so we can't spot the planets in the pictures.

Now, we can determine where planets "should be" by means of measuring the energy levels of a star system to the star, by measuring the "wobble" of a star, and by other indirect means. This is why a planet can, for most purposes, be considered Dark Matter - because it's matter that doesn't emit electromagnetic radiation (ie, light).

This is why it's so hard to see planets, even in our own solar system.