Dwarf elliptical galaxy PGC 29388. Credit: ESA/Hubble & NASA, T. Armandroff
As beautiful as the surrounding space may be, the sparkling galaxy in the foreground of this image from the NASA/ESA Hubble Space Telescope undeniably steals the show.
This spotlight-hogging galaxy, seen set against a backdrop of more distant galaxies of all shapes and sizes, is known as PGC 29388. Although it dominates in this image, this galaxy is a small player on the cosmic stage, and is known as a dwarf elliptical galaxy. As the “dwarf” moniker suggests, the galaxy is on the smaller side, and boasts a “mere” 100 million to a few billion stars — a very small number indeed when compared to the Milky Way’s population of around 250 to 400 billion stellar residents.
Dwarf elliptical galaxies, or dEs, are elliptical galaxies that are smaller than ordinary elliptical galaxies. They are quite common in galaxy groups and clusters, and are usually companions to other galaxies.
Dwarf galaxies are generally associated with a nearby large galaxy, referred to as its parent. Many dwarf galaxies lie in a very thin plane extending from the poles of their parent (such as the Andromeda galaxy) in direct contradiction to the accepted idea that a halo of Dark Matter surrounds the parent and that dwarfs should be formed all over.
Concepts in String Theory suggest one novel possibility for how dwarfs are formed. https://www.youtube.com/watch?v=uuG4yy-vW84