GENERAL KNOWLEDGE

Detailed explanation-1: -The fact that stars come in different colours is not a mere curiosity. The colour provides a fundamental piece of data in stellar astrophysics-the surface temperature of the star. The hottest stars are blue and the coldest are red, contrary to the use of colours in art and in our daily experience.

Detailed explanation-2: -The hottest stars tend to appear blue or blue-white, whereas the coolest stars are red. A color index of a star is the difference in the magnitudes measured at any two wavelengths and is one way that astronomers measure and express the temperature of stars.

Detailed explanation-3: -Why are blue stars so hot? Blue stars are blue because they’re very hot. This sounds wrong, because in the everyday world-for example on weather maps-red means hot and blue means cold. But blue light carries more energy than red light, which means it needs a hotter radiation source to produce it.

Detailed explanation-4: -A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They have luminosity class I and spectral class B9 or earlier. Blue supergiants are found towards the top left of the Hertzsprung–Russell diagram, above and to the right of the main sequence.