NGC 4689 has ring-like feature in its inner regions. Surrounding the inner ring lies a zone of bright, flocculent spiral structure with a ring-like boundary. Outside this zone is a well-defined, diffuse outer ring which is an unusual feature for a late-type galaxy like NGC 4689.[7]
Star formation
The star forming disk in NGC 4689 has been truncated which means that the amount of star formation has been reduced significantly. This truncation may have been caused by an interaction with intracluster medium of the Virgo Cluster causing the galaxy to lose much of its interstellar medium in an effect known as ram-pressure stripping.[7] Due to its reduced amount of star formation, NGC 4689 has been classified as an anemic galaxy.[8]
^Kuno, Nario; Sato, Naoko; Nakanishi, Hiroyuki; Hirota, Akihiko; Tosaki, Tomoka; Shioya, Yasuhiro; Sorai, Kazuo; Nakai, Naomasa; Nishiyama, Kota; Vila-Vilaro ́, Baltsar (2007). "Nobeyama CO Atlas of Nearby Spiral Galaxies: Distribution of Molecular Gas in Barred and Non-barred Spiral Galaxies". Publications of the Astronomical Society of Japan. 59: 117–166. arXiv:0705.2678. Bibcode:2007PASJ...59..117K. doi:10.1093/pasj/59.1.117. S2CID14076941.
^Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Frogel, Jay A.; Eskridge, Paul B.; Pogge, Richard W.; Gallagher, Andrew; Iams, Joel (2 May 2002). "Arm Structure in Anemic Spiral Galaxies". The Astronomical Journal. 124 (2): 777–781. arXiv:astro-ph/0205105. Bibcode:2002AJ....124..777E. doi:10.1086/341613. S2CID7757634.