It's hard to pinpoint one specific person who first realized stars were distant suns, as this understanding evolved over centuries. Here's a breakdown:

* Ancient Greeks: Philosophers like Anaxagoras (500-428 BC) and Aristarchus (310-230 BC) theorized that the stars might be similar to the Sun, but lacked the tools to prove it.

* 16th Century: Nicolaus Copernicus (1473-1543) proposed the heliocentric model, placing the Sun at the center of the solar system. This was a crucial step towards understanding the vast distances involved.

* 17th Century: Galileo Galilei (1564-1642) used his telescope to observe the Milky Way and discovered that it was composed of countless stars. This observation strengthened the idea that stars were not just points of light, but distant suns.

* 19th Century: Friedrich Bessel (1784-1846) measured the parallax of a star (61 Cygni) for the first time. This proved that stars are indeed at immense distances from Earth.

So, it wasn't a single "Eureka!" moment, but a gradual progression of observations, theories, and technological advancements that led to the understanding that stars are distant suns.