Question

Compared to the star it evolved from, a red giant is
(A) hotter and brighter
(B) hotter and dimmer
(C) cooler and brighter
(D) cooler and dimmer

Answer 1

Hint: A red giant is also the star but it looks like a giant star of low mass in the phase of stellar evolution. The outer atmosphere looks inflated and makes the radius large and the surface temperature around five thousand kelvin or lower than this temperature.

Complete step by step solution
The appearance of the red giant star is in the form of yellow orange to red, and it includes some spectral colours. The red giant is different in the way by which the red giant will generate energy. The most of the reed giant are stars on the branch of the red giant that are still fusing the hydrogen into the helium in the outer shell of the inert helium core. Many of the bright stars are well known that the stars are red giants, because that the stars are more luminous and moderate.

The red giant is the star that has exhausted the hydrogen supply to its core and begins the nuclear fusion of the hydrogen in the shell surrounding the core. They are having the radius which is more than the radius of the sun. But the outer area of the red giant is lower in temperature and makes the appearance of the reddish orange. When the lower energy density of the envelope, the red giants are having the luminous than the luminous of the sun, it is because of the great size of the red giant. And the red giant is cooler and brighter than the star.

Hence, the option (C) is the correct answer.

Note: The stars which come under the branch of the red giant having the luminous up to nearly three thousand times of the luminous of the sun. And the stars which come under the branch of the red giant have the radius up to nearly two hundred times the radius of the sun.