Dragonfly 44
Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster. Observations of the velocity dispersion suggest a mass of about one trillion solar masses, about the same as the mass of the Milky Way; the galaxy shows no evidence of rotation. This is also consistent with about 90 globular clusters observed around Dragonfly 44. However, the galaxy emits only 1% of the light emitted by the Milky Way. The galaxy was discovered with the Dragonfly Telephoto Array.
To determine the amount of dark matter in this galaxy, they used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours over a period of six nights so they could determine the galaxy's mass.
The scientists then used the Gemini Multi-Object Spectrograph on the 8-m Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy's core.
In August 2016, astronomers reported that this galaxy might be made almost entirely of dark matter.
