Star A has temperature of 3000K, starB is 12000K. How do the luminosity ( or thermal radiation) compare? Wh?

Question

Star A has temperature of 3000K, starB is 12000K. How do the luminosity ( or thermal radiation) compare? Wh?

Answer 1

You've also got to know their surface areas.

Answer 2

According to the Stefan-Boltzmann law

L = 4 pi R^2 sigma T^4

the flux per unit surface area can be compared, and the color.

Star B puts out 256 times as much energy every second per unit surface area. But without the size, you cannot say what the luminosity is.

The color is also different. Star A would be red (and actually puts out most energy in the near-infrared!, while star B would be bluish-white.