ISOHDFS 27

ISOHDFS 27 is a spiral galaxy in the constellation Tucana located approximately from Earth. Discovered in the Hubble Deep Field South survey, it is the most massive spiral galaxy found in the survey, measuring at a total mass of 1.04 trillion times the mass of the Sun within, making it about four times as massive as the Milky Way. In addition, the baryonic mass has been calculated to be half of the dynamical mass, about. Although it was once described as the most massive known spiral galaxy, larger possible mass estimates have been suggested for other spiral galaxies such as UGC 2885, Andromeda Galaxy, and as well as Milky Way.
Although ISOHDFS 27 does not have any known measured isophotal diameter, an angular diameter of about 7 arcseconds has been suggested, corresponding to a diameter of in diameter, nearly as large as the Andromeda Galaxy.