Quotes from the news wire:
Normally, you wouldn’t be able to detect the light of an individual star in that pixel, but because these pulsating stars are so bright and the pulsation is so strong, we could see that about a quarter of the pixels of the image changed their brightness. They changed it because the pixels contain these pulsating stars.
It leads to a different way of looking at galaxies, where we always seen them as completely static in the sky, unchanging on human time scales, in fact, they are shimmering. They are shimmering constantly. Every pixel in the image is getting brighter and fainter and they are not constant at all, which is sort of a different way of almost thinking about the light in the universe.