Page:Astronomy for Everybody.djvu/328

What we know of the constellations dates from Ptolemy, who lived in the second century after Christ. His names are still in use. As many of them are those of the gods, goddesses, and heroes of Grecian mythology—Perseus, Andromeda, Cepheus, Hercules, etc.—it seems likely that they were assigned during or after the heroic age.

In modern times quite a number of new constellations have been carved out of or drawn between the older ones. This is especially the case in the southern hemisphere, which was imperfectly known to the ancient Greeks.