The shape of galaxies: reconfiguring Hubble's tuning fork
Using citizen science project Galaxy Zoo, citizen astronomers may have overturned a century-old galaxy classification system.
By Shaoni Bhattacharya
October 8, 2020 at 8:56 am
In 1926 the American astronomer Edwin Hubble developed a classification system to describe the evolution of galaxies and their development from an elliptical to a spiral formation.
Hubble allocated numbers to the elliptical galaxies to characterise each one’s ellipticity, E0 being nearly round and E7 being very elliptical.
Spiral galaxies, according to Hubble’s system, were assigned letters from a to c according to how tightly wound they are, Sa being very tightly wound and Sc being more loosely wound.
The system was dubbed ‘Hubble’s tuning fork’ because of the way in which galactic evolution appears to generally go one of two ways once an elliptical galaxy begins evolving into a spiral (scroll further down for an illustration of this).
More:
https://www.skyatnightmagazine.com/space-science/hubble-tuning-fork-shape-galaxies/
