Astronomy, Astrophysics, and Space Science

(Juipter, NASA)

Astronomy and astrophysics involves the study and understanding of all large objects. Astronomers observe everything from the planets in our solar system to the galaxies we inhabit, and even the universe itself. 

Astronomy is the study and measurement of the physical properties of extraterrestrial objects. This helps to develop physical laws and theorems that can be applied to large-scale worlds (i.e. planets, stars, galaxies and the entire universe). 

Astrophysics is the application of the laws and theorems of physics to information gathered by observing extraterrestrial objects. This can be used to predict the presence of unseen objects, as well as the future motion and evolution of observed objects. 

The best way to think about space science is as applying physical science to everything in space. In this way, astrophysics is one of the space sciences. Some other space sciences include astrobiology, chemistry, and helioseismology, but the list goes on. Almost every physical science has some form of application in space. 

Astrophysics is the branch of space science that applies the laws of physics and chemistry in the quest to understand the universe and our place in it. This field explores topics such as the birth, life and death of stars, planets, galaxies, nebulae and other objects in the universe. It has two sibling sciences, astronomy and cosmology, although the lines between these branches can blur. 

Astrophysics creates physical theories of small and medium-sized objects and structures in the universe. Astronomy measures the position, luminosity, motion, and other characteristics of celestial bodies. Cosmology covers the largest structures of the universe and the universe as a whole.

All celestial bodies emit or reflect light (or electromagnetic radiation). This radiation is spread over a wide range of wavelengths, including (but not limited to) the visible spectrum (i.e. the colors we see every day). 

To help astronomers properly understand what's going on, they need to look at more than just visible light from these objects. To this end, a large number of different telescopes have been built. 

When we look at a star, the light we see is only a fraction of the radiation from that star. So if astronomers only look at visible light in the universe, they can only see a tiny part of the picture. For this reason, astronomers design and build telescopes (some that don't look like telescopes at all) to observe all different wavelengths of light. 

Despite varying sizes and shapes, all telescopes work on the same principle: collect, focus and record radiation. Different telescopes are categorized by the wavelength range or band they are designed to collect: gamma rays, X-rays, UV (ultraviolet), optical, IR (infrared), microwaves or radio.