Concrete is the most common artificial composite material of all and typically consists of loose stones (aggregate) held with a matrix of cement. Concrete is a very robust material, much more robust than cement, and will not compress or shatter even under quite a large compressive force.
2) Y-axis contains absolute brightness Why do astronomers use the H-R Diagram? Astronomers use H-R Diagrams to classify stars and to understand how stars change over time.
Regulus, also known as Alpha Leonis, is the brightest star in the constellation Leo and the 21st brightest star in the night sky. It has an apparent magnitude of 1.35 and lies at a distance of 79.3 light years, or 24.3 parsecs, from Earth. Alpha Leonis is not really a single star, but a multiple star system.