ESO 439-26
ESO 439-26 is a white dwarf star. It was considered the least luminous white dwarf known. Located 140 light years away from the Sun, it is roughly 10 billion years old and has a temperature of 4560 Kelvin. Thus, despite being classified as a "white dwarf", it would actually appear yellowish in color.
This finding is however based on a too large parallax. Gaia measurement of the parallax shows a more distant source and therefore an absolute magnitude of MG=15.0 mag. For example the white dwarf WD J2147–4035 has MG=17.7 mag, making this white dwarf less luminous. The updated MV is 15.46, using the Gaia parallax and the apparent V-magnitude from Ruiz et al..