Stellar Evolution: Observational Hertzsprung-Russel

Ejnar Hertzsprung and Henry Norris Russel developed a vital tool used to study stellar evolution, a scatter graph that plots a star’s spectral type respective to their absolute magnitude, which is the observational Hertzsprung-Russel Diagram, or the temperature of stars relative to its luminosity, the theoretical H-R diagram. Stars have specific evolutionary stages based on their initial mass, dictating its internal structure and means of energy production. The phases in stellar evolution correspond to alterations in luminosity and temperature. There are three main regions present on the diagram, the most dominant is the main sequence which is where approximately 90% of all known stars lie and extends from the bottom right-hand corner to the …show more content…
Solar cores of high temperatures, generate energy quicker, therefore higher temperature stars are more luminescent. Stars located on the main sequence, referred to as “dwarfs”, must generate power through hydrogen and helium nuclear fusion in their solar core and be in thermal equilibrium, the balance between luminosity and energy generation, and hydrostatic equilibrium, equality between pressure and gravity. Following the mass-luminosity relationship, hot, bright and high mass stars are located on the upper left, ranging in temperatures from roughly 2 x 104 to 4 x104 Kelvin and a luminosity of approximately 104 solar units. The upper main sequence stars have a mass greater than 1.5 solar masses and generate energy by solely nuclear fusion involving hydrogen and helium. Their internal structure is generally a convective core and a radiative envelope. As hydrogen is fused into helium, the nuclei which remain, travel quicker in order to sustain hydrostatic equilibrium causing fusion to occur more rapidly than previously thus, as stars age the more luminescent they