$\mathrm{D}_{n}4000$ gradients
Some have younger stars in the middle and older ones around the edges.
Technical definition
A measure of the change in the 4000 Å break, a spectral feature indicative of age, from the center to the edges of a galaxy.
Some have younger stars in the middle and older ones around the edges.
A measure of the change in the 4000 Å break, a spectral feature indicative of age, from the center to the edges of a galaxy.