Star Formation and Stellar Evolution

Stars form in dense clouds of dust and gas, eventually becoming protostars. As they grow, nuclear reactions begin, leading to fully formed stars. Stars vary in size and lifespan, with massive stars burning hotter and living shorter lives. Many stars exist in binary systems, while some, like our sun, are solitary. Brown dwarfs are failed stars that never ignite nuclear reactions. Stars eventually exhaust their hydrogen, becoming red giants and then white dwarfs, with their outer layers forming planetary nebulae.

What triggers the collapse of a cloud of dust and gas to form a protostar?

• Magnetic fields

• External pressure

• Radiation

• Gravity

At what temperature do nuclear reactions start in a protostar?

• 1 million Kelvin

• 5 million Kelvin

• 10 million Kelvin

• 15 million Kelvin

How long does it take for a star like the Sun to form?

• 500 million years

• 100 million years

• 50 million years

• 10 million years

Which of the following stars is more massive than the Sun?

• Vega

• Wolf 359

• Proxima Centauri

• Barnard's Star

What color does a very massive star burn?

• Green

• White-blue

• Yellow

• Red

What percentage of stars are in binary systems?

• 10-20%

• 30-40%

• 70-80%

• 50-60%

What is a brown dwarf?

• A type of planet

• A black hole

• A failed star

• A type of galaxy

What happens to a star when it exhausts its hydrogen?

• It turns into a neutron star

• It explodes as a supernova

• It becomes a red giant

• It becomes a black hole

What is the final stage of a star like the Sun?

• Neutron star

• Black hole

• White dwarf

• Red supergiant

What are planetary nebulae?

• Illuminated outer parts of a red giant

• Clusters of young stars

• Remnants of supernova explosions

• Regions where planets form