the dereference between; astrophysics, astronomy, cosmology and space science

wolfspirit

hi
i am looking at uni courses and i a a bit confused between the differences between; astrophysics, astronomy, cosmology and space science in terms of what is covered in each . Can anyone help please.
Ryan

Nabeshin

Cosmology is the study of the universe as a whole, this term is unambiguous.

As for the others, there isn't really any universal definition. Astrophysics and astronomy are almost synonymous, with astrophysics more often being used for work involving numerical computations of things like neutron stars or stellar winds, and astronomy perhaps dealing more with nebulae, dust clouds, interstellar media, and things like this. But again the terms don't really have a clear definition. I hear space sciences used more often do describe things like planetary science, such as studying the geology of Mars or Venus, or perhaps the atmosphere of Jupiter or an exoplanet.

twofish-quant

In some circles, astrophysics is theoretical whereas astronomy is observational.

Planetary science has more similarities with geology than with say stellar astronomy.

The other thing is that the distinctions sometimes appear for curious reasons. For example, in most university departments, there isn't a separate field of "heliophysics" because the sun is just another star. However, when NASA sets up their committees, they have a "heliophysics division" which is separate from the "astrophysics division". The reason is that from the physics point of view the sun is "just another star" but from the "can we build a space ship to visit the place and take ultra close pictures" point of view, it's very different.