Messier Index/M90

Messier 90 (also known as M90 and NGC 4569) is a spiral galaxy about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.

Membership of the Virgo Cluster
Messier 90 is a member of the Virgo Cluster. The galaxy is located approximately 1°.5 away from the subgroup centered on Messier 87. As a consequence of the galaxy's interaction with the intracluster medium in the Virgo Cluster, the galaxy has lost much of its interstellar medium. As a result of this process, which is referred to as ram pressure stripping, the galaxy's interstellar medium and star formation regions appear truncated compared to similar galaxies outside the Virgo Cluster.

Star formation activity
As stated above, the star formation in Messier 90 appears truncated. Consequently, the galaxy's spiral arms appear to be smooth and featureless, rather than knotted like galaxies with extended star formation. However, the center of Messier 90 appears to be a site of significant star formation activity. Multiple supernovae in the nucleus have produced 'superwinds' that are blowing the galaxy's interstellar medium outward into the intracluster medium.

Blueshift
The spectrum of Messier 90 is blueshifted, which indicates that it is moving towards the Earth. In contrast, the spectra of most other galaxies are redshifted. The blueshift was originally used to argue that Messier 90 was actually an object in the foreground of the Virgo Cluster. However, since the phenomenon was limited mostly to galaxies in the same part of the sky as the Virgo Cluster, it appeared that this inference based on the blueshift was incorrect. Instead, the blueshift is thought to be evidence for the large range in velocities of objects within the Virgo Cluster itself.

Distance measurements
Low levels of H I gas prevents using the Tully-Fisher relation to estimate the distance to Messier 90.

Companion galaxies
Messier 90 has a satellite galaxy (IC 3583) which is an irregular galaxy.