Main-Sequence Stars and Stellar Evolution

The video explores the life cycle of a low-mass star, starting from a nebula, progressing through stages like protostar, main sequence, and red giant, and ending as a white dwarf. It also discusses the theoretical black dwarf stage. The video emphasizes the vastness of the universe, with billions of stars and galaxies, and encourages viewers to engage with more content.

How many stars are estimated to be in the Milky Way galaxy?

• 30 billion

• 3 trillion

• 300 billion

• 300 million

What is the initial stage of a star called before hydrogen starts burning?

• Protostar

• White dwarf

• Main-sequence star

• Red giant

What percentage of known stars are main-sequence stars?

• 100%

• 90%

• 70%

• 50%

What happens to a main-sequence star when it runs out of hydrogen?

• It turns into a red giant

• It becomes a protostar

• It forms a black hole

• It becomes a white dwarf

What is the temperature of a red giant's outer layer?

• 40000 Kelvin

• 20000 Kelvin

• 10000 Kelvin

• 5000 Kelvin

What celestial bodies will the Sun absorb as it becomes a red giant?

• Venus and Earth

• Mercury and Venus

• Earth and Mars

• Mars and Jupiter

What is formed when the outer shells of a red giant separate from its core?

• A black hole

• A neutron star

• A supernova

• A planetary nebula

What remains at the center after a planetary nebula dissipates?

• A black hole

• A neutron star

• A white dwarf

• A protostar

What is the theoretical final stage of a white dwarf?

• A supernova

• A neutron star

• A black dwarf

• A red giant

Why have scientists not discovered a black dwarf yet?

• They are hidden by other stars

• They emit no light or energy

• They are too small

• They emit too much light