SOLAR SYSTEM

Detailed explanation-1: -A star converts hydrogen atoms into helium over its course of life at its core. Eventually, the hydrogen fuel runs out, and the internal reaction stops. Without the reactions occurring at the core, a star contracts inward through gravity causing it to expand.

Detailed explanation-2: -A star like our Sun will become a white dwarf when it has exhausted its nuclear fuel. Near the end of its nuclear burning stage, such a star expels most of its outer material (creating a planetary nebula) until only the hot (T > 100, 000 K) core remains, which then settles down to become a young white dwarf.

Detailed explanation-3: -A star at the stage in its life cycle when it stops burning hydrogen, begins burning helium, and expands to a large, low-density star.

Detailed explanation-4: -After puffing off its outer layers, the star collapses to form a very dense white dwarf. One teaspoon of material from a white dwarf would weigh up to 100 tonnes. Over billions of years, the white dwarf cools and becomes invisible. Stars heavier than eight times the mass of the Sun end their lives very suddenly.

Detailed explanation-5: -A red giant forms after a star has run out of hydrogen fuel for nuclear fusion, and has begun the process of dying. A star maintains its stability through a fine balance between its own gravity, which holds it together, and the outwards pressure from ongoing thermonuclear fusion processes taking place at its core.

Detailed explanation-6: -If the star is big enough to fuse hydrogen atoms into helium, it will enter the phase that our Sun is in, called the main sequence phase. A star will enjoy most of its life in the main sequence phase. At this point nuclear fusion is turning hydrogen into helium.

Detailed explanation-7: -The hydrogen burning in the shell heats the surrounding mass of the star and causes it to expand. The radius of the star increases and the surface temperature drops. The luminosity of the star increases dramatically, and it becomes a red giant.