Three supernovae have been observed in NGC664. American astronomer John Huchra discovered SN1972L (type unknown, mag.15)[5] on 3 September 1972. The other 2 supernovae are: SN2000dj (typeII, mag.17.4)[6] and SN2006ei (typeIc, mag.18.5).[7]
NGC 735 is a member of the NGC669 group (also known as LGG 37). This group contains 34 galaxies, of which 15 are in NGC, 11 are in UGC, and 3 are in IC.[8]
^"SN1972L". Transient Name Server. IAU. Retrieved 23 August 2024.
^"SN2000dj". Transient Name Server. IAU. Retrieved 23 August 2024.
^"SN2006ei". Transient Name Server. IAU. Retrieved 23 August 2024.
^Garcia, A. M. (1993). "General study of group membership. II. Determination of nearby groups". Astronomy and Astrophysics Supplement Series. 100: 47. Bibcode:1993A&AS..100...47G.