This image includes NGC 2814, an irregular galaxy in the Holmberg 124 group, caught by the Hubble Telescope. Credit: ESA/Hubble & & NASA, C. Kilpatrick
This Hubble Picture of the Week includes NGC 2814, an irregular galaxy that lies roughly 85 million light-years from Earth. In this image, which was captured utilizing Hubbles Advanced Camera for Surveys (ACS), the galaxy appears to be rather isolated: visually, it looks a little like a loose stroke of intense paint throughout a dark background.
Nevertheless, looks can be deceiving. NGC 2814 in fact has three close (in astronomical terms) stellar neighbors: a side-on spiral galaxy known as NGC 2820; an irregular galaxy called IC 2458; and a face-on non-barred spiral galaxy called NGC 2805. Collectively, the four galaxies make up a galaxy group called Holmberg 124. In some literature, these galaxies are referred to as a group of late-type galaxies.
Clarifying Galactic Classifications
The terms late-type describes spiral and irregular galaxies, while early-type describes elliptical galaxies. This rather confusing terms has actually caused a typical mistaken belief within the astronomy community. It is still rather widely thought that Edwin Hubble inaccurately thought that elliptical galaxies were the evolutionary precursors to spiral and irregular galaxies, which that is the reason ellipticals are classed as early-type and spirals and irregulars are classified as late-type.
NGC 2814 in fact has 3 close (in huge terms) stellar next-door neighbors: a side-on spiral galaxy known as NGC 2820; an irregular galaxy named IC 2458; and a face-on non-barred spiral galaxy called NGC 2805. The terms late-type refers to spiral and irregular galaxies, while early-type refers to elliptical galaxies. It is still quite widely thought that Edwin Hubble incorrectly believed that elliptical galaxies were the evolutionary precursors to spiral and irregular galaxies, and that is the factor why ellipticals are classed as early-type and irregulars and spirals are classified as late-type.
This misunderstanding is due to the Hubble tuning fork of stellar category, which visually shows galaxy types following elliptical to spiral, in a series that could quickly be interpreted as a temporal advancement.
Hubble actually embraced the terms early-type and late-type from much older astronomical terminology for outstanding categories, and did not mean to state that ellipticals were actually evolutionary precursors to spiral and irregular galaxies. … refers to place in the series, and temporal undertones are made at ones peri.”.
Despite Hubble himself being quite emphatic on this topic, the misconception continues nearly a hundred years later on, and maybe supplies an instructional example of why it is handy to classify things with easy-to-interpret terms from the beginning!