According to the 1994 volume of "Astronomy and Astrophysics Abstracts" in the 10 month period between January and October, 1994 there were some 11665 papers published in over 1000 journals by 15,673 astronomers. These articles covered some 2493 topics.
There are 11 main categories of research:
1... Astronomical Instrumentation and Techniques 2... Positional Astronomy and Celestial Mechanics 3... Space Research 4... Theoretical Physics 5... The Sun 6... The Earth 7... The Planetary System 8... Stars 9... Interstellar Matter and Nebulae 10.. Radio sources, X-ray sources, Cosmic Rays 11.. Stellar Systems, Galaxies, Cosmology
Under these main headings are 89 sub topics. For example, under 'Stellar Systems' there is:
1... Kinematics and Dynamics 2... Stellar Associations 3... Open Clusters 4... Globular Clusters 5... Galaxies 6... Magellanic Clouds 7... Normal Galaxies 8... Active Galaxies 9... Quasars 10.. Galaxy Groups and Clusters 11.. Cosmology
Each paper may have more than one 'key word' if it covers more than one aspect of a problem. Keywords are an even finer level of defining the general contents of a paper. At this level of description, in 1994 there were 2496 topics covered by 15,000 scientists. For example, under 'K' we find the key words:
1... K Dwarfs 2... K Giants 3... K Stars 4... Kerr Black Holes 5... Kirkwood Gaps 6... Kuiper Belt