What are the Application of Chandrasekhar Limit?

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Super computers and eight telescopes stationed on five continents were used to develop huge data on black holes. This data was later proved by which theory?