2/22 Warm-Up

What is the primary factor that allows a star to enter the main sequence phase?

• The star's ability to reflect light

• The fusion of helium into heavier elements

• The fusion of hydrogen into helium

• The star's rotation speed

During the main sequence phase, how does a star maintain its stability?

• By cooling down and contracting

• Through the balance between gravitational forces and the pressure from nuclear fusion

• By expanding and releasing energy

• Through the absorption of interstellar material

What triggers a star's transition from the main sequence phase to the red giant stage?

• Loss of all hydrogen fuel

• Increase in magnetic activity

• Hydrogen fuel exhaustion in the core, leading to helium fusion

• Collision with another star

What characteristic change occurs in a star as it enters the red giant phase?

• It becomes smaller and hotter

• It becomes larger and cooler on the surface

• It starts to spin faster

• It becomes completely solid

What is the ultimate fate of a low to medium mass star after the red giant phase?

• It becomes a black hole

• It turns into a neutron star

• It explodes as a supernova

• It sheds its outer layers and leaves behind a white dwarf

During a supernova explosion, what is primarily responsible for the incredible increase in brightness?

• The sudden release of gravitational energy

• The ignition of all remaining fuel at once

• The collapse of the core and the subsequent shock wave

• The fusion of all elements into iron

What is a necessary condition for a star to end its life as a black hole?

• It must be a binary star system

• It must have a mass several times that of the Sun

• It must have exhausted all nuclear fuel

• It must be part of a star cluster

What happens to the core of a massive star just before a supernova explosion?

• It expands rapidly

• It cools down and solidifies

• It undergoes a sudden collapse

• It splits into two parts

Why do stars much more massive than the Sun not form into white dwarfs after their nuclear fuel is exhausted?

• Their cores are too hot for a white dwarf to form

• They lose too much mass in the red giant phase

• Their gravitational pull is too strong, leading to further collapse

• They turn directly into black holes without collapsing

After the main sequence phase, what will a HIGH mass star become?

• planetary nebula

• red giant

• red supergiant

• white dwarf