Research the history of Vulcan to explain how its existence was tested and finally disproved

Research the history of Vulcan to explain how its existence was tested and finally disproved.

Class, you have had previous situation where you were asked to conduct research.

Let us think about how and where you can find the facts that you need to respond to this question:

What requirements does a source have to meet before you can use it as support of an academic argument?
How do you evaluate sources?