The Realm of Galaxies

 

The Realm of Galaxies in the Constellation Virgo. Seestar S30 402x10 sec subs in Alt-Az mode. Data captured from Suffolk in spring 2025. Image Credit: Pip Stakkert.

"The above image depicts a deep-sky view of the Realm of Galaxies in the constellation Virgo, a region that is one of the richest nearby concentrations of galaxies observable from Earth. This area is dominated by the Virgo Cluster, the central component of the larger Virgo Supercluster, of which the Local Group (containing the Milky Way and Andromeda) is a small part. The line of galaxies (running vertically centre right) is known as Markarian's Chain.

The Realm of Galaxies

The term "Realm of Galaxies," introduced by Edwin Hubble in the mid-20th century, refers specifically to the Virgo Cluster of galaxies, situated at a distance of about 54–65 million light-years from Earth.

This cluster contains more than 1,300 confirmed galaxies, with estimates of up to 2,000 members. The population includes giant ellipticals, spirals, irregular galaxies, and numerous dwarf ellipticals.

The Virgo Cluster is gravitationally bound and exerts significant dynamical influence on the motions of galaxies in the Local Supercluster.

The image above shows a wide-field survey view of the Virgo Cluster core region. Several important galaxies can be identified :

Elliptical Giants (Center-right, glowing regions)

Bright, extended objects with smooth light profiles correspond to giant elliptical galaxies such as M84 (NGC 4374) and M86 (NGC 4406).

These galaxies dominate the dense cluster core and are rich in globular clusters and hot X-ray gas.

M87 (Virgo A)

This supergiant elliptical galaxy is among the most massive galaxies in the local universe, containing a supermassive black hole of ~6.5 billion solar masses, famously imaged by the Event Horizon Telescope.

Spiral Galaxies

Edge-on streak-like structures visible across the field correspond to spirals, such as NGC 4388 or NGC 4438, which are undergoing gravitational interactions and ram-pressure stripping due to the intracluster medium.

Intracluster Medium & Dwarfs

The faint reddish diffuse glow represents background stars, dust, and possibly intracluster light produced by stripped stars from past galactic interactions.

The field is peppered with dwarf ellipticals and irregular galaxies, which are abundant in the cluster but often difficult to discern individually without deep surveys.

Scientific Importance

The Virgo Cluster serves as a laboratory for galaxy evolution, as interactions and environmental effects (tidal stripping, ram-pressure stripping, and mergers) can be directly studied.

It provides an anchor point for the extragalactic distance scale, with Cepheids and surface brightness fluctuations used to refine measurements of the Hubble constant.

The cluster's gravitational well shapes the Local Velocity Field, influencing the peculiar motions of nearby galaxies, including the Milky Way".- Professor G.P.T Chat visiting astrophycist at the JPO.