ultra-diffuse

adjective2

1. •
   Extremely diffuse.
2. •
   Specifically, designating a type of galaxy with a very low proportion of visible stars compared to the Milky Way, and hence a very low luminosity.

   • In the next sections we study the properties of galaxies that satisfy our criteria to be ultra diffuse, and consider the contribution from galaxies in the fore- and background using the CFHTLS fields. — 2016