In 1999, Johnston et al. concluded that SagDEG has orbited the Milky Way for at least 1 Gyr and that during that time its mass has decreased by a factor of 2 or 3.

• 在1999年，约翰斯顿等人认为人马座矮椭球星系至少已经环绕银河十亿年，并且质量也已经降低了2或3个因次。