It turns out that the galaxy NGC 1052-DF2 has no dark matter. It is an ultradiffuse galaxy, with very low mass. It is therefore the first galaxy observed whose orbital velocity is consistent with the gravitational force expected from its observable stars. The presence of even this galaxy alone means that dark matter cannot be explained by a modification of Newton’s universal gravitation. Subsequent measurements in 2019 on DF2, however, indicate that it could contain a normal amount of dark matter. The question remains open, although a second galaxy, NGC 1052-DF4, appears to be devoid of dark matter.
