Final answer:
The surface temperature of Antares can be estimated using Wien's displacement law, with a calculated temperature of around 3400 K, consistent with its classification as a red supergiant. The red appearance of Antares links to its cooler surface temperature compared to hotter stars.
Step-by-step explanation:
The student asked what the surface temperature of the star Antares is, given that it emits the greatest intensity of radiation at a wavelength of 853 nm. To find the temperature of Antares, we can utilize the Wien's displacement law. This physical law states that the black-body radiation curve for different temperatures will peak at different wavelengths that are inversely related to the temperature.
Wien's displacement law is λ_max = (b/T), where λ_max is the peak wavelength in meters, T is the temperature in Kelvin, and b is a constant of proportionality called Wien's displacement constant (b ≈ 2.8977719 x 10^-3 m K).
To calculate the estimated surface temperature of Antares, we can rearrange Wien's law to solve for T: T = b / λ_max. For Antares, λ_max is 853 nm, which is 853 x 10^-9 meters. Plugging this into the equation, we get:
T = (2.8977719 x 10^-3 m K) / (853 x 10^-9 m) ≈ 3400 K
This temperature is consistent with a red supergiant star, which Antares is classified as. Red supergiant stars, such as Antares, are indeed cooler than hotter blue or white stars but are very luminous due to their large size.
The red appearance of Antares in the sky is a result of this lower surface temperature and the fact that cooler stars emit more intensity at longer (red) wavelengths. The color of a star is related to its surface temperature, with red stars being cooler and blue stars being hotter. Antares, as a red supergiant, does not emit most of its energy in the ultraviolet (which would be the case for very hot stars), but in the infrared and at the red end of the visible spectrum.
Given its red color and lower temperature, we would not expect an H II region around Antares. H II regions are typically found around very hot and young stars that emit copious ultraviolet radiation capable of ionizing hydrogen. Antares, being cooler, is not likely to create such a region.