Canopus was a star.
Background information Edit
Canopus and Alpha Carinae are depicted as being two separate stars on a star chart first seen in Star Trek VI: The Undiscovered Country and subsequently reused in a number of Star Trek episodes. In reality, these are two different names for the same star.  This contradiction is also noted in the Star Trek Encyclopedia (4th ed., vol. 1, p. 115) and, according to Star Trek: Star Charts (p. 65) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Canopus (Alpha Carinae) is a star in the Beta Quadrant. The primary was a F-class star.
For Star Trek: First Contact, Alex Jaeger created a ship size comparison chart for Industrial Light & Magic. On this chart, one of the names considered for the Norway-class starship was the USS Canopus.