Answer to Question #89608 in Astronomy | Astrophysics for Sujon Rana

Question

you have discovered a new star in milky way.your new star is red and has 3/5 temperature of our sun.the new star emits a total power that is 1000000 times greater than the power emitted by our sun.
1.Determine the spectral(I.e.spectral classification) of the new star.
2.How many times bigger is the radius of the new star compared to the radius of our sun?

Answer 1

The effective temperature of our Sun is around 5780 K.

The temperature of the new star is 3470K - it is M spectral class.

As its luminosity $10^6$ times greater than luminosity of Sun, looking at Hertzsprung–Russell diagram, we deduce this is red supergiant.

They are typically several hundred to over a thousand times the radius of the Sun.