A Hertzsprung-Russell (H-R) diagram is a plot of a star's absolute magnitude (luminosity) against its temperature. When this is plotted for many stars, it can be seen that most lie in a band across the middle of the graph, known as the Main Sequence. This is where stars spend most of their lifetime, while they are burning hydrogen. Hot stars are found at the upper left hand end of the Main Sequence while cooler stars are found to the lower right. Stars are all classified according to temperature and spectral type, with the hotter stars called ‘O’ type stars and the coolest called ‘M’ type stars. The order of classification is:
O-B-A-F-G-K-M
And can be remembered using the mnemonic “Oh Be A Fine Girl, Kiss Me.
During its lifetime a star will evolve on the H-R diagram depending on its mass.
沒有留言:
張貼留言