EVERYDAY SCIENCE

Detailed explanation-1: -When a sun-like star having average mass runs out of fuel-hydrogen, its atmosphere expands and the star becomes a red-giant star. The star would leave the main-sequence stage and enter the red-giant stage in which the pressure of the core is high which pushes the atmosphere outwards and thus the star expands.

Detailed explanation-2: -Once a star has exhausted its supply of hydrogen in its core, leaving nothing but helium, the outward force created by fusion starts to decrease and the star can no longer maintain equilibrium. The force of gravity becomes greater than the force from internal pressure and the star begins to collapse.

Detailed explanation-3: -"This causes the star to expand enormously and increase in luminosity-the star becomes a red giant.” Red giant stars bloat to 62 million to 620 million miles in diameter (100 million to 1 billion kilometers)-100 to 1, 000 times wider than our sun is today.

Detailed explanation-4: -So what happens to the sun when it runs out of its hydrogen fuel? JOSHUA: Right, so the sun is about four and a half billion years old, and in about five billion years, it’s going to start to run out of its fuel. And then it will expand into what’s known as a red giant.

Detailed explanation-5: -When a main sequence star begins to run out of hydrogen fuel, the star becomes a red giant or a red supergiant. After a low-or medium-mass star has become a red giant, the outer parts grow bigger and drift into space, forming a cloud of gas called a planetary nebula.