Cosmological Metrics

Measure Fact
Galaxy sizeMost of the galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) — Wikipedia
SMBH jet sizesJets can exceed millions of parsecs in length. — Wikipedia
SMBH jet durationJets can have a duration of up to ~10 M years nonstop
How far apart are galaxies?Average galaxy spacing is a few megaparsecs. [2]

The average spacing is somewhere in the range of 10 – 100 times the size of the biggest galaxies. [2]

Galaxies are not distributed uniformly, but instead are grouped into clusters, which are themselves grouped into superclusters. [2]

Galaxies vary enormously in size, with dwarf galaxies around a thousand times smaller than the biggest galaxies. [2]

Galaxies are much, muchmuch closer relative to their size than stars are. That’s why galaxy collisions are quite frequent while stellar collisions are rare to the point of non-existence. [2]
How many stars are in a galaxy?Galaxies range in size from dwarfs with just a few hundred million (108) stars to giants with one hundred trillion (1014) stars — Wikipedia
What is in intergalactic space?The space between galaxies is filled with a tenuous gas (the intergalactic medium) having an average density of less than one atom per cubic meter. — Wikipedia

“If you took a cubic meter, there would be less than one atom in it,” says Michael Shull, an astronomer at the University of Colorado Boulder. “But when you add it all up, it’s somewhere between 50 and 80% of all the ordinary matter out there.” — [1]

The IGM under the influence of a galaxy’s gravitational pull slowly accumulates onto the galaxy at a rate of about one solar mass (equal to the mass of the sun) per year, which is about the rate of star formation in the disk of the Milky Way. [1]

“IGM is the gas that feeds star formation in galaxies,” Shull said. “If we didn’t still have gas falling in, being pulled in by gravity, star formation would slowly grind to a halt as the gas [in the galaxy] gets used up.” [1]

“Even outside galaxies, an [you] could find at least one proton, on average, in every cubic meter. Also, one electron and half a billion photons and neutrinos, all left over from the big bang.” [3]

See my blog post Particle Rain to understand how the IGM is part of the recycling universe.

J Mark Morris : San Diego : California