The Virgo cluster is composed of over 2,000 galaxies and is Earth’s nearest large galaxy cluster.
Dwarf galaxies closest to Virgo’s crowded center contained more globular clusters than those farther away. The universe is expanding faster than predicted. Some unknown ingredients are at work in the cosmos.
The Hubble tension is the mismatch between the locally measured expansion rate of the universe and the one inferred from the cosmic microwave background measurements by Planck. Dark energy is the primary force driving the universe’s sped-up expansion of the universe. The Hubble constant doesn’t hold up. The cosmic distance ladder isn’t accurate. The ladder’s best estimate isn’t good enough.
The overall average energy density of the universe is zero, and this does not change as it expands. The thickness of dark energy remains constant as the universe expands, so the amount of energy in an expanding volume increases. The universe is mostly a vacuum with a few trillion galaxies within. The Big Bang kicked off an inflationary vacuum. It had a super-high energy density and repulsive gravity, causing it to expand. The more of it there was, the greater the repulsion and the faster it grew.
Many factors contribute to the density of matter. The most fundamental of them is Planck’s constant. It creates an atomic-scale balance between location and momentum. That is the same balance that also determines the size of atoms.
The density of dark matter is the equivalent of 2.5 protons per cubic meter throughout the universe. We don’t know the size of the particles. The distribution of dark matter is not uniform. Globular clusters form in episodes of intense star formation that shape galaxies. Their compact dimensions and luminosity make them easily observable, and they are good tracers of the properties of their host galaxy. Globular clusters formed from giant molecular clouds or enormous masses of gas that form stars as they collapse. Globular clusters cannot form today because less free gas is available now than at the beginning of the universe.
We know the relation between the size of nuclei and their mass, which shows that as a first approximation, nuclear density is constant. But there are subtle differences because nuclear mass defect varies slightly with the mass number so the nuclear density is also not perfectly constant. When looking at this binding number dependence on the mass, number one finds that iron is probably the densest nucleus from the whole periodic table.
