Nova comes from the Latin novus, meaning "new." In astronomy, a nova is a star that suddenly increases dramatically in brightness — from a previously dim star to one that may rival the brightest in the sky for weeks before fading.
Nova as a girl's name is a contemporary phenomenon. It entered the U.S. top 1000 in 2011 and has risen explosively. Today it sits in the U.S.
Nova does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Nova reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.