Spiral galaxies are the most common type of galaxies and they look like spirals, with long arms winding toward a bright bulge at the centre. Scientists call this centre "Black hole."
Generally, vishnu is depicted as relaxing on the divine serpent Sesha accompanied by Goddess Lakshmi in the Ksheera-sagara.
The colour of the galaxy is milky white, which can be compared to the Ksheera-sagara.
In cosmological terms our Galaxy which is spiral, is called Milkyway Galaxy. Synonymously, in Puranas Lakshmi-Narayana are said to be relaxing on the Sesha in Ksheera-sagara.
So, the depiction of Narayana and Lakshmi relaxing on the coil serpent Sesha-talpa-sai can be described scientifically as Lakshmi and Narayana residing at the centre of galaxy.