Missing dark matter & shadows from a black hole, Hubble continues to unlock cosmic mysteries

[Elderberry]

NASA Spaceflight by Chris Gebhardt November 30, 2020

It’s a constant of the universe.  Dark matter – a key ingredient for the formation and evolution of galaxies is present in whatever galaxy is observed.

That is until NGC 1052-DF2 was discovered – a galaxy missing most of its dark matter.  A year later, galaxy NGC 1052-DF4 was discovered 45 million light years from Earth… and it too was missing most of its dark matter.

But how is this possible?

Dark matter accounts for approximately 85% of the matter of the universe and 25% of its overall mass-energy density.  As it does not interact in an observable way with electromagnetic fields and does not appear to interact in any way with electromagnetic radiation, it cannot be easily detected.  Thus its name: “dark” matter.

Evidence of its existence, however, comes from observed galaxies and the laws of gravity that show that galaxies would fly apart given their observable masses, not move the way they do, and never have formed at all unless an unseen form of matter (dark matter) was present in significant quantities as well.

Other indirect evidence for dark matter include gravitational lensing and cosmic microwave background observations, the universe’s observed structure, and mass location during galactic collisions.

More: https://www.nasaspaceflight.com/2020/11/dark-matter-shadows-from-black-hole-hubble/