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How is the Sun classified as a G2 V star?
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Star
Stars in the open cluster NGC 290, as seen by the Hubble Space Telescope.
The Sun is classified as a G2 V star based on the MK (Yerkes) system, which combines spectral type and luminosity class to categorize stars.1
- G2 (Spectral Type): This designation comes from the Harvard system, which classifies stars primarily by their surface temperature. The G class represents yellow stars with surface temperatures ranging from 5,000 to 6,000 K. The "2" is a decimal subdivision indicating that the Sun is among the hotter stars within the G class, with a surface temperature of approximately 5,800 K.123
- V (Luminosity Class): This indicates that the Sun is a main-sequence star, also known as a dwarf star. These stars are in a state of hydrostatic equilibrium, meaning they are stable because the inward pressure of gravity is balanced by the outward pressure generated by the nuclear fusion of hydrogen into helium in their cores.314