Betelgeuse vs Rigel: Understanding Surface Area Discrepancy

If the stars Betelgeuse and Rigel each have the same luminosity, but the temperature of Betelgeuse is lower than Rigel, which star has the greater surface area?

A. Betelgeuse B. Rigel C. They are the same size D. There is insufficient information to answer this question.

Answer:

Option A is Correct.

When comparing the stars Betelgeuse and Rigel in terms of surface area, Betelgeuse takes the lead despite both stars having the same luminosity. This outcome is due to the temperature difference between the two stars.

Rigel is known to have a lower temperature compared to Betelgeuse. Despite both stars having equal brightness, the temperature variance impacts their surface areas. In general, red stars like Betelgeuse have lower surface temperatures compared to blue-white stars like Rigel.

At around 3,500 Kelvin, Betelgeuse's surface temperature is relatively warm, whereas Rigel's temperature is even lower. Despite Betelgeuse's intense brightness, which is around 40,000 times that of our Sun, its surface remains cooler at less than 4000 K.

Therefore, in the scenario where Betelgeuse and Rigel have the same luminosity but differing temperatures, Betelgeuse's larger surface area is a result of its lower temperature compared to Rigel.