... galaxies . ... Globular cluster NGC 2808, elliptical galaxy NGC 2986, and the Sextans Dwarf . ... A cold surprise . The discovery of an ultra-cool white dwarf in Virgo raises more questions than it answers. ... Which mechanism could cause ultra-cool white dwarfs to cool so quickly is still unknown, but scientists believe it might be key to understanding how early stars in the galaxy formed and died. ... However, ultra-cool white dwarfs, such as the one Wolf found, are much colder than these stars. ...