The word "nova" has the same meaning in Spanish and English; it refers to a star that shows a sudden large increase in brightness and then slowly returns to its original state. According to Oxford Dictionaries, the term is derived from the Latin word "novus," which means "new."
The phrase "no va" means "it doesn't go" in Spanish. As About.com explains, this meaning has helped create an urban legend surrounding the sales of Chevy Nova cars in Spanish-speaking countries. According to the legend, Chevy Nova cars sold terribly in Spanish-speaking countries because people had no interest in purchasing a car that "doesn't go." This urban legend is completely untrue. "Nova" and "no va" do not have the same meaning. In reality the Chevy Nova sold reasonably well in Latin America.