What are the most actively researched areas in astronomy today?

According to the 1994 issue of Astronomy and Astrophysics Abstracts there are 2496 topics under which some 16,000 research papers could be filed. The largest categories are as follows:

Active Galactic Nuclei

Black Holes

Comets

Cosmology

Galactic Structure and Evolution

Gamma-ray Astronomy

Infrared Astronomy

Interstellar Gas and Dust

Magnetic Fields

Molecular Clouds

Planetary Astronomy

Pulsars

Quasars

Radio Sources

Solar Physics

Star Formation

Stellar Evolution

Supernova

X-Ray Astronomy