why Scientist can said about thing billions of years ago as if they are confirmed fact.?

There are a large number of balls of ice and rock of various sizes scattered around the solar system. Some are small enough that they are irregularly shaped. Some have highly elliptical orbits. Some are very, very small. So part of the difficulty is that there is not an agreed upon definition of what a 'planet' really is. By one definition, Pluto is not a planet, but rather is the first of a class of medium sized balls of ice and rock to be discovered at the edges of our system (the Kuiper belt objects). There are many others, some of which are comparable in size. Furthermore, these objects are far enough away from the sun that they don't reflect much light back to us, so they are very hard to locate.

On the other hand, we can estimate the distances to some fairly bright galaxies and determine that they are billions of light years away. That means that the light from these galaxies has taken a billion years to get to us. That, in turn, means that we are seeing now what happened there billions of years ago. This allows us to say what the universe was like at that time with some confidence.

This is not an absolute thing. Scientists can take educated guesses, and they can use what they do know to fill in the blank spaces. Otherwise, sometimes looking into the stars could be looking into the past: a supernova which could very well have occurred billions of years before can be seen as if it were live because the light and energy from the supernova took a billion years to get to earth. Light and energy from the sun takes three minutes to get to earth, so observing the sun is seeing it as it was three minutes before the current time. Thus, a star which is further away can be observed at a point even further in the distant past.

No (good) scientist says anything as if it is a confirmed fact.

Ilya R is quite right - a good scientist can only say "to the best of our testing ability this is as close as we can get to 'factual' knowledge for the time being"

We can't be certain of anything really. All we have are theories supported by experiments in the present time until a better theory emerges.

I believe the reason Big Bang for instance gets more attention is due to the fact that most who go into astrophysics have little interest about the planets around us... its seen as boring, while really far out there, the stuff noone looked at has much more potential for fame as well as keeping you interested but that's just MY THEORY

the 9 planets in the solar system