John Lennon was born on 9 October 1940.
He formed the Beatles in 1957, in the Aquarius (groups, partnerships) phase of his life. Note his moon is in Aquarius as well.
1958-60 Aquarius continued
He married Cynthia Powell in 1962 in the Aries phase of his life, where he he has his ascendant (being seen and heard) and a supporting trine from Pluto (tremendous force). As a result, by the end of his Aries phase Beatlemania is in full force, 1964. In the unstable Gemini phase, very early on, in 1968, where he gets a supporting trine from his Aquarius moon, his infidelity breaks up his marriage and results in a new marriage to Yoko Ono in 1969.
Divorce from Yoko Ono was in 1973, in his Cancer phase, where he squares his Aries ascendant and Capricorn midheaven.
Early in his Leo phase he is assassinated, in 1980, as he has Pluto (death, violence, tremendous force) in early Leo, at 4 Leo, directly opposing aforementioned natal Aquarius moon at 3 Aquarius. Also, squared by his natal Mercury at 4 Scorpio. He goes out in a blaze of glory in his Leo (glory, accolades) phase.
Note that for the world, 1979-89 is the Gemini phase. 1980 is in early Gemini, which would trine his natal moon in the above configuration and make him a popular (moon – popularity, relationships) martyr or hero.