Redshift. What’s the redshift? Found it.
“In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10^−7, implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10^11 solar masses) of cool dense (volume density ≃ 1 cm^−3) gas, which is in conflict with current cosmological simulations.”
> It gets stranger: The four quasars are nestled in a gigantic cloud of cold hydrogen gas that theories say shouldn’t exist either. The gas would normally heat up as it collapses—but the cloud Hennawi and his colleagues found has a temperature of only about 10,000°C. “By cosmological standards,” says Weinberg, “that’s actually pretty cold. You’d expect the temperature to be more like ten million degrees.”
Huh? Surely the cloud could be a lot colder than that.
> Just for the record, the Milky Way’s black hole, weighing in at four million suns, is too much of a lightweight to have ever been a quasar. Nearby Andromeda’s, by contrast, at 100 million suns, probably was at some point
That’s a useful bit of info. If Andromeda’s core was ever a quasar, there may still be a remnant somewhere, such as a weak bipolar radio signal.