1. Peak wavelength: The peak wavelength of the thermal radiation spectrum of a star is inversely proportional to its temperature. Therefore, the 8000 K star will have a peak wavelength that is shorter than that of the 4000 K star. In fact, the peak wavelength of the 8000 K star will be in the ultraviolet part of the spectrum, while the peak wavelength of the 4000 K star will be in the visible part of the spectrum.

2. Overall brightness: The total amount of radiation emitted by a star is proportional to the fourth power of its temperature. Therefore, the 8000 K star will be much brighter than the 4000 K star. In fact, the 8000 K star will be about 16 times brighter than the 4000 K star.