DIFFUSE GALAXIES - Astronomers discovered another new galaxy that contains almost zero dark matter. But diffuse galaxies aren’t new, since Dragonfly 44 was in the news a few years ago. Here’s the difference.
DRAGONFLY 44 - Astronomers reported In August 2016 its composition was made almost entirely of dark matter. A dark ultra-diffuse galaxy with similar mass to our own, but strangely, showed no evidence of rotation. With 1% the light we’re used to, its 99% darker than the Milky Way.
NGC 1052-DF2 - This clear ultra diffuse galaxy contains only 1/200 the number of stars and also has roughly the size as our own galaxy. Here’s where things get weird. It doesn’t look like a spiral or elliptical galaxy but appears malformed. It contains at least 400 times less dark matter than normal and possibly none at all. This large fuzzy diffuse galaxy is so clear, distant galaxies can be seen behind it.
What’s so unusual about this? - Typically galaxies coalesce from dark matter forming dark matter halos, gas blobs turning into stars beginning to build, organized in typical galaxies such as the Milky Way with orderly rotation and shape.
The discovery demonstrates dark matter is separable from galaxies since NGC 1052-DF2 has none. Dark matter is conventionally believed to be integral structurally to all galaxies. NGC 1052-DF2 challenges notions of how galaxies form. Interesting stuff, indeed.