Hubble's law
Videos
Hubble's law, officially the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. Thus, the farther a galaxy
Three steps to the Hubble constant
Fit of redshift velocities to Hubble's law. Various estimates for the Hubble constant exist.
A variety of possible recessional velocity vs. redshift functions including the simple linear relation v = cz; a variety of possible shapes from theories related to general relativity; and a curve that does not permit speeds faster than light in accordance with special relativity. All curves are linear at low redshifts.
Bridge diagram showing different measurements of the Hubble constant, 2021
GW170817
Videos
GW170817 was a gravitational wave observed by the LIGO and Virgo detectors on 17 August 2017, originating within the shell elliptical galaxy NGC 4993, about 140 million light years away. The wave was
Artistic concept: two neutron stars merge
Light curves at various wavelengths of kilonova in NGC 4993
Artist's impression of strontium emerging from a neutron star merger.
PIA21423 Surface of TRAPPIST 1f