Compilation of the nature of objects

The physical nature of objects is collected from the literature and from the surveys loaded in HyperLeda.

Although HyperLeda is intended to be a database of extragalactic objects, it is not possible to restrict it to galaxies alone. Often, the physical nature of an object is not known at the time of discovery, and it formally only appears as an extended source, while its extragalactic nature is merely a presumption. Other observations may confirm or change the earlier classification. Because the data are never excluded from the database, HyperLeda contains virtually all kinds of celestial objects. The homogenization process combines the different classifications for each object, automatically chooses the most precise or assigns an undetermined nature in case of inconsistency. These cases are marked for human control to possibly solve the inconsistency.

There are a number of reasons why HyperLeda stores stars.

• This is pretty important to know whether a galaxy is in the close vicinity of a bright star. It can affect the parameters determination, the cross-identifications, there are artifacts in some surveys near bright stars, and so on.
• The nature of objects is not always clear from a single survey, and some classifications may be uncertain (QSO and stars may be confused as both are point-sources). Having the stars in HyperLeda improves the cross-identifications of new data, and helps to ascertain the nature.
• If we are interested in galaxies, it is still important to know that an object is (probably) not a galaxy.