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.
Spica or Alpha Virginis (Alp Vir) is the brightest naked eye star in the constellation Virgo. With an apparent magnitude of 0.98v, Spica is the 15th brightest star in the entire sky (see: 50 Brightest Stars).Its absolute magnitude is -3.55 and its distance is 262 light years.The Equinox J2000 equatorial coordinates are RA = 13h 25m 11.6s, Dec = -11Â° 09' 41.pica has a spectral type of B1V, a surface temperature of 22,400Â° Kelvin and a luminosity 12,100 times the Sun. It has a mass of 10.3 solar masses and a diameter 7.4 times the Sun. The image above shows the uncropped view of Spica (North is up) through the Takahashi E-180 Astrograph.