The core contracts as the outer layers expand. These stars have depleted their hydrogen supply and are very old.
As stars begin to die, they become giants and supergiants (above the main sequence). These stars are in the most stable part of their existence this stage generally lasts for about 5 billion years. For these stars, the hotter they are, the brighter. 
Most stars, including the sun, are "main sequence stars," fueled by nuclear fusion converting hydrogen into helium. This diagram shows that there are 3 very different types of stars: On it, astronomers plot stars' color, temperature, luminosity, spectral type, and evolutionary stage. its luminosity (intrinsic brightness or absolute magnitude). The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. O and B stars are uncommon but very bright M stars are common but dim.Īn easy mnemonic for remembering these is: "Oh be a fine guy/girl, kiss me." In order of decreasing temperature, O, B, A, F, G, K, and M. Stars are classified by their spectra (the elements that they absorb) and their temperature. The Sun is a as a G2V type star, a yellow dwarf and a main sequence star. Our subscribers' grade-level estimate for this page: Today's featured page: Science Fields Vocabulary Word List Major Stars and Star Systems - Zoom Astronomy Star Classification - Zoom Astronomy Advertisement.Į is a user-supported site.Īs a bonus, site members have access to a banner-ad-free version of the site, with print-friendly pages.
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