Well I was just wondering that what exactly difference between Cosmology and Astronomy...?
I won't accept a difference. However, I gained the impression that Astronomy is more often used in mapping and observation contexts and Cosmology in calculating and modelling contexts. Nevertheless, it's artificial. (personal opinion)
I have these distinctions in my mind:
Astronomy: A science concerned with discovering and cataloguing celestial bodies. To map the Universe, if you will.
Cosmology: A science concerned with the history of the Universe. How it developed over time and is developing today. How galaxies and other systems came to be and where they are going.
Astrophysics: A science concerned with the "behavior" of celestial bodies, identifying what forces they exert and are subject to, as well as figuring out what happens at the atomic level in stars, pulsars, black holes etc. It gives Cosmology the tools it requires to make its discoveries and explanations.
Astrology: A ridiculous pseudoscience that has no logical grounding whatsoever, and should not be studied by anyone sane of mind.
In this way, Neil Degrasse Tyson and Stephen Hawking would be cosmologists and astrophysicists, but not astronomers. I don't think they care about classifying recently discovered galaxies!
Nature does not care about how we define our sciences or what words we use to describe them. (despite the fact we distinguish them, thanks for your input Nantes).
How can you discuss the nuclear fusion process in a star without chemistry? The only reason I am familiar with the periodic table is because of Astronomy.
Then we develop new sciences like astrobiology and so on.
One of my favorite aspects of exploring astronomy is that is opened my eyes up to the other sciences as well.
Sounds about right to me, but often it's the case that the observations made by astronomy are the raw data from which the theoretical science (cosmology) proceeds.
Conversely cosmological theories can lead to predictions of phenomena that might later be discovered by astronomers.
Gravitational lensing is a good example.
A person need not be working exclusively in one field they may be doing both simultaneously, personally I'd place Tyson in that some-of-both category.
Separate names with a comma.