The sources of light that have been found to be collections of billions of stars, and not individual stars, are galaxies.

Here's why:

* Galaxies are vast collections of stars, gas, dust, and dark matter. They are held together by gravity and can contain hundreds of billions of stars, as well as planets, nebulae, and other celestial objects.

* Individual stars are much smaller and less luminous than entire galaxies. While we can see individual stars in our own Milky Way galaxy, most of the light we see from distant galaxies comes from the combined light of billions of stars.

* Galaxies come in different shapes and sizes. Some are spiral, some are elliptical, and some are irregular. They can also vary in their age, composition, and luminosity.

So, when you see a faint, fuzzy patch of light in the night sky, you're likely looking at a galaxy – a collection of billions of stars!