This image was taken by an advanced high-performance NASA Hubble Space Telescope wide-field camera covering the optical and near parts of the spectrum. And although hundreds of distant stars and galaxies are located on this photo, there is one nuance - Hubble then studied a specific object!
No, there is no mistake. The camera uses two detectors: the first deals with the object under investigation, in this case the star cluster NGC 299, and the second adjusts the space “under” it. And this is what we are seeing here.
From a technical point of view, this is like a “backdrop” or “background” for a real object of study. But space is so active that this field of celestial bodies is of interest in itself. At first it seems that these are only stars, but spiral galaxies are also located here (swirling “arms” are moving away from the center). Fuzzy galaxies can be ellipses. And in some of them there are millions of stars, but they are so far away that we see only a general light, resembling the size of a whole single star. Bright blue dots are hot stars with a cross-shaped glow created by the secondary mirror of the telescope. Red dots are colder stars in the red giant stage (when the star dies and expands).