How many planets were there in 1984?

Answer 1

As far as is known to modern Astronomy, no planets have been created or destroyed since 1984, and the total number has been essentially stable since then.

However, at the time, Pluto was still considered to be a planet, so in writings of the time you'll see references to the "nine planets". Astronomers have since decided that it's foolish to include as tiny an object as Pluto in the same category as Jupiter (many of whose moons are significantly larger than Pluto), and current articles only reference eight Solar planets.