What did Herschel initially suspect the object he found on March 13, 1781, might be?

Answer

A comet

Upon first observation, Herschel thought the object was a comet, but subsequent tracking confirmed its orbital path indicated it was a new planet.

What did Herschel initially suspect the object he found on March 13, 1781, might be?
astronomyUranustelescopeAstronomerdiscoveries