The upper range for temperatures of stars is approximately 50,000 Kelvin (K). This corresponds to the hottest and most luminous stars known as O-type and B-type stars. These stars emit intense ultraviolet radiation and have surface temperatures far hotter than our Sun, which has a surface temperature of approximately 5,778 K. As stars reach this extreme temperature range, they exhibit unique spectral features and characteristics associated with their intense radiation and high internal energy.