God said to Abraham “Gaze now toward the heavens, and count the stars if you are able to count them … so shall be your progeny.” (Genesis 15:5) Abraham might not have bothered to count them all, and relied on the Lord’s word instead, but it did not stop the sages of the Talmud from taking a crack at computing the contents of the heavens. As it is written, “Twelve constellations have I created in the firmament, and for each constellation I have created thirty hosts, and for each host I have created thirty legions, and for each legion I have created thirty cohorts, and for each cohort I have created thirty maniples, and for each maniple I have created thirty camps, and to each camp I have attached three hundred and sixty five thousands of myriads of stars ….” (Berachot 32b) The sages were aware that the stars are not just randomly distributed over the firmament; instead they are clustered (for each constellation I have created thirty hosts, and for each host …). Astronomers confirmed this by stating that galaxies “live” in great clusters, and even super clusters like swarms of bees. They also use the number 30 in describing the number of clusters within clusters of stars. The number of stars stated in the Talmud is 1.06434 x 1018. (10 to the 18th power) The number of stars in the universe counted by the best astronomical estimate of somewhere between 1018 and 1020, which is amazingly close to the Talmudic count.
Parry, Aaron. The Complete Idiot’s Guide to the Talmud (Complete Idiot’s Guides (Lifestyle Paperback)) (p. 183). DK Publishing. Kindle Edition.
Worth reading, also for not-Jewish readers