stars

What is the life cycle path of a low-mass star similar to our Sun?

Nebula -> Protostar -> Main Sequence Star -> Red Giant -> Planetary Nebula -> White Dwarf.

What is the life cycle path of a high-mass star?

Nebula -> Protostar -> Main Sequence Star -> Red Supergiant -> Supernova -> Neutron Star or Black Hole.

What process powers main sequence stars, and what elements are primarily involved?

Nuclear fusion, primarily converting hydrogen into helium in their cores.

What two stellar properties are plotted on the axes of an HR Diagram?

The Y-axis plots Luminosity (or Absolute Magnitude) and the X-axis plots Surface Temperature (or Spectral Type/Color).

Where do most stars, including our Sun, spend the majority of their lives on the HR Diagram?

On the Main Sequence, a diagonal band from the upper-left to the lower-right.

Where are Red Giants and Supergiants located on the HR Diagram?

In the upper-right section, indicating they are very large stars with cool surface temperatures and very high luminosity.

Where are White Dwarfs located on the HR Diagram?

In the lower-left section, indicating they are very small and dense stars with hot surface temperatures and very low luminosity.

How can the HR Diagram help us understand stellar evolution?

Stars move on the HR Diagram as they age, transitioning from the Main Sequence to the Red Giant region and then to the White Dwarf region.

What is stellar nucleosynthesis?

The process by which stars create new, heavier elements from lighter ones through nuclear fusion reactions.

What elements are primarily formed during the main sequence phase of a star's life?

Primarily helium from the fusion of hydrogen.

As a star ages past the main sequence, what heavier elements can it begin to fuse?

It can fuse helium into carbon and oxygen.

In very massive stars, fusion can continue to form elements up to what atomic number?

Up to iron (Fe), as fusion into iron is the last energy-producing stage.

Why can't stars produce energy by fusing elements heavier than iron?

Fusing elements heavier than iron requires energy rather than releasing it.

How are elements heavier than iron formed?

They are primarily formed during supernova explosions or neutron star mergers through rapid neutron capture processes.

What is a nebula in the context of star formation?

A large cloud of gas and dust in space, where stars are born.

What is a protostar?

A contracting mass of gas and dust that represents an early stage in the formation of a star, before nuclear fusion begins.

What is a planetary nebula?

An expanding shell of ionized gas ejected from a dying low-mass star at the end of its asymptotic giant branch phase.

What is a supernova?

A powerful and luminous stellar explosion, occurring either when a massive star runs out of fuel and collapses or when a white dwarf in a binary system accretes too much matter.

What force is responsible for the initial collapse of a nebula to form a protostar?

Gravity.

What is the primary factor that determines a star's evolutionary path and lifespan?

Its initial mass.

What principle supports a main sequence star against gravitational collapse?

Hydrostatic equilibrium, where the outward pressure from nuclear fusion balances the inward pull of gravity.

What is the remnant of a high-mass star after a Type II supernova if its core is too massive to form a neutron star?

A black hole.

What type of pressure supports a white dwarf against gravitational collapse?

Electron degeneracy pressure.

What defines the 'event horizon' of a black hole?

The boundary beyond which nothing, not even light, can escape the black hole's gravitational pull.