Cepheid Variable in NGC 3370

Here we see a "movie" of 12 consecutive epochs of a long period (~50 days) Cepheid variable. The Cepheid is in the center of a crowded region of stars. The resolution of HST is required to pick out the variable star from its neighbors. The star was caught initially fading before suddenly doubling in brightness, then declining again to its faintest point over 4-5 weeks.