If it exists, it would be composed mostly of dark matter and interstellar gas with few stars.
[4] Observational evidence for this galaxy was presented in 2015,[5] based on the claimed discovery of four Cepheid variable stars by Sukanya Chakrabarti (RIT) and collaborators.
[2] [9] In November 2015, a group led by P. Pietrukowicz published a paper arguing against the existence of Galaxy X.
These authors argued that the four stars were not actually Cepheid variable stars and that their distances might be very different than claimed in the discovery paper of Chakrabarti et al. On this basis, the authors stated that "there is no evidence for a background dwarf galaxy".
[10] However the galaxy is still regarded to exist by others, with the stars being examined to be actual Cepheids.