Hubble looks at a late-type galaxy

This NASA Hubble Area Telescope picture options NGC 2814, an irregular galaxy that lies about 85 million light-years from Earth. On this picture, which was captured utilizing Hubble’s Superior Digital camera for Surveys, the galaxy seems to be fairly remoted: visually, it seems to be a bit like a free stroke of vivid paint throughout a darkish background. Nevertheless, seems to be might be deceiving.

NGC 2814 really has three shut (in astronomical phrases) galactic neighbors, not seen on this picture: a side-on spiral galaxy often known as NGC 2820, an irregular galaxy named IC 2458, and a face-on non-barred spiral galaxy referred to as NGC 2805. Collectively, the 4 galaxies make up a galaxy group often known as Holmberg 124. These galaxies are typically known as a bunch of “late-type galaxies.”

The terminology “late-type” refers to spiral and irregular galaxies, whereas “early sort” refers to elliptical galaxies. This relatively complicated terminology has led to a typical misconception throughout the astronomy neighborhood. It’s nonetheless fairly broadly believed that Edwin Hubble inaccurately thought that elliptical galaxies have been the evolutionary precursors to spiral and irregular galaxies, and that that’s the reason why ellipticals are classed as early sort and spirals and irregulars are classed as late-type.

This false impression is as a result of Hubble tuning fork of galactic classification, which visually exhibits galaxy varieties continuing from elliptical to spiral, in a sequence that would simply be interpreted as a temporal evolution. Nevertheless, Hubble really adopted the phrases early sort and late-type from a lot older astronomical terminology for stellar classifications, and didn’t imply to state that ellipticals have been actually evolutionary precursors to spiral and irregular galaxies. In actual fact, he explicitly stated in a 1927 paper that “the nomenclature … [early and late] … refers to place within the sequence, and temporal connotations are made at one’s peril.”

Regardless of Hubble himself being fairly emphatic on this matter, the misunderstanding persists nearly 100 years later, and maybe offers an instructive instance of why it’s useful to categorise issues with easy-to-interpret terminology from the get-go.