Galaxy cluster Abell S0740. The giant elliptical galaxy ESO 325-4 at the cluster's center. Hubble Space Telescope.
ESO 325-4 acts as a strong gravitational lens, bending the light of a
background galaxy into arcs. In 2018, a combined analysis of the lensed arcs
and the motions of the galaxy's own stars was used to test general relativity
on galactic scales, measuring the spacetime curvature generated per unit mass
as γ = 0.97 ± 0.09 — consistent with the value of exactly 1 predicted by
Einstein, and at the time the most precise extragalactic
test of general relativity.[3][4]
Notes
↑The given distance in the overview of NED of 133±8.718 megaparsecs (433.8±28.43million light-years) was based on an estimate using the Tully-Fischer relation. The distance estimate in this infobox was based on the galaxy's redshift.
12The quick-look major axis physical diameters given by NED of 110.77 by 86.40 kiloparsecs (361,000 by 282,000 light-years) and 62.67 by 50.14 kiloparsecs (204,000 by 164,000 light-years) were based on a distance estimate of 133±8.718 megaparsecs (433.8±28.43million light-years). The quoted diameters in this infobox was based on NED's provided scale "Virgo + GA + Shapley" of 973 pc/arcsec multiplied with the given angular diameters.
