Andromeda XXXVI (And XXXVI) is an ultra-faint dwarf spheroidal galaxy located at a distance of 776 kiloparsecs, or 2.53 million light-years, from the Sun in the constellation of Andromeda, within the Local Group. It is one of the faintest ultra-faint dwarf galaxies of M31 discovered to date.
Discovery Andromeda XXXVI was first identified by astrophotographer and amateur astronomer Giuseppe Donatiello during a visual inspection of archival public data from the Pan-Andromeda Archaeological Survey (PAndAS), conducted with the Canada-France-Hawaii Telescope, and subsequently confirmed through observations using the Gran Telescopio Canarias. The results were published in the scientific journal Astronomy & Astrophysics on June 25, 2026.
Physical characteristics Andromeda XXXVI is classified as an ultra-faint dwarf spheroidal galaxy with an effective half-light radius of light-years ( parsecs). The galaxy’s ellipticity is extremely low, approximately , which gives its projection on the sky a nearly perfect spherical shape. The position angle of the major axis is θ = . The absolute magnitude of the galaxy in the visible range is estimated at MV = .
Its projected distance from the center of the Andromeda Galaxy is about 388,000 light-years. Given that the virial radius of M31’s gravitational influence is estimated at 850,000 light-years, Andromeda XXXVI lies deep within its halo and is a gravitationally bound satellite.
Color-magnitude diagram modeling indicates that the system's stellar population is approximately 12.5 billion years old, with a metallicity [Fe/H] = -2.5. Such a low abundance of elements heavier than helium suggests that the galaxy formed in the early Universe, underwent only a brief initial burst of star formation, and is completely devoid of the modern interstellar gas required to trigger the formation of new stars.
See also List of Andromeda's satellite galaxies Dwarf spheroidal galaxy (dSph) Andromeda Galaxy
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