NGC 5907 has an anomalously low metallicity and few detectable giant stars, being apparently composed almost entirely of dwarf stars. It is a member of the NGC 5866 Group.
NGC 5907 has long been considered a prototypical example of a warped spiral in relative isolation. In 1998, a faint ring structure, likely caused by a disrupted dwarf spheroidal galaxy, was first observed around the galaxy.This challenged the assumption of isolation and suggests the gravitational perturbations induced by the stream progenitor may be the cause for the warp. Then, in 2008, an international team of astronomers announced the presence of an extended double loop tidal stream coiling around the galaxy. The existence of part of these tidal streams has been recently challenged by some deeper surveys, which show only a single knee-shaped stream as opposed to the full double loop structure. This shorter stream has a length of 45′ in the sky (or a physical size of 220 kpc) and has a surface brightness ranging from 27.6 mag/arcsec2 at its brightest to 28.8 at its faintest.
An ultraluminous X-ray source, NGC 5907 ULX-1, is located in the galaxy. This source is also called an ultraluminous X-ray pulsar (ULXP) because it exhibits a rapid pulsation effect. This pulsation has a period of 5.7 days and is caused by a rotating neutron star orbiting a high mass companion. The neutron star itself has a spin period of 1.13 seconds and seems to be accelerating; its period ten years prior was 1.43 seconds. It is one of the brightest such source yet discovered with a luminosity over 1041 erg/s (7 orders of magnitude more luminous than the Sun). Notably, its peak luminosity is over 1000 times greater than the Eddington luminosity for a neutron star.
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