Categorisations of object types in SIMBAD

Astronomical objectsmay be classified into types in many ways, and the evolution of such categorisations changes with new discoveries and progress in astrophysicalunderstanding. The SIMBADdatabase contains information on astronomical objectsthat have been studied in the published literature, including a field that specifies astronomical objecttypes. As a record that is derived entirely from the literature, a given astronomical objectin SIMBADmay have multiple object types, and the list of object typesmust be maintained and updated. The SIMBAD object typelist currently contains some 200 types, that are organised into a hierarchy based on astrophysicalconcepts. The hierarchical structure also includes relations between object types, and this facilitates searches of SIMBADto obtain lists of all of the astronomical objectsin a given category independently of the publisher or the year of publication. We will explain the organisation of astronomical objecttypes in SIMBADand how they may be used in queries of the SIMBADdatabase, and visualised on all-sky maps.