During the 1960s, theorists like Jeremiah Ostriker used early computers to determine that spiral galaxies would be unstable and "fly apart" without a massive spherical halo of unseen matter. This theoretical need found concrete evidence through the pionee

During the 1960s, theorists like Jeremiah Ostriker used early computers to determine that spiral galaxies would be unstable and "fly apart" without a massive spherical halo of unseen matter. This theoretical need found concrete evidence through the pioneering work of Vera Rubin and Kent Ford. By observing the Andromeda galaxy, they discovered that rotational velocities did not diminish at the outer edges, a phenomenon called "flattening the curve." This proved that a significant amount of invisible mass must exist to provide the necessary gravity. To map this mass, modern astronomers use gravitational lensing, an effect predicted by Einstein where gravity bends light from distant objects. This work continues in Chile at the Vera Rubin Observatory, which is designed to map the distribution of dark matter across space and time. (2/8)
2020 ESA EUCLID