Why do we think there is a lot of dark matter in the clusters of galaxies?

Why do we think there is a lot of dark matter in clusters of galaxies? gravity of visible matter. Gravitational lensing lets us measure mass even when we can’t see it.

What evidence do we have that galaxies have extended halos of dark matter?

Researchers used the Sloan Digital Sky Survey to find evidence that the dark matter halos surrounding galaxies and galaxy clusters have a discernible edge. Research from the University of Pennsylvania could shed light on the distribution of one of the most mysterious substances in the universe.

What is the observational evidence that indicates the Milky Way is within a halo of dark matter?

Observational evidence indicates that there is a super massive black hole located at the center of the Galaxy, one that weighs about 5 million times as much as the Sun. One way we can tell the mass of this humongous black hole is to measure how fast stars are moving around it.

Why does dark matter form halos?

Cosmological evolution of small perturbations. The overdensities start out as very small perturbations on top of the smooth density. They evolve under the influence of gravity and other physical processes and eventually grow so large that they form the bound, virialized objects known as dark matter halos.

What makes dark matter and dark energy so mysterious?

Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. One explanation for dark energy is that it is a property of space. Because this energy is a property of space itself, it would not be diluted as space expands.

What’s the difference between dark matter and gravity?

Dark matter produces an attractive force (gravity), while dark energy produces a repulsive force (antigravity). Together, they make up 96 percent of the universe—and we can’t see either. Astronomers know dark matter exists because visible matter doesn’t have enough gravitational muster to hold galaxies together.