05 How Stars Work Free Online FlashCards

What is hydrostatic equilibrium in a star?

Hydrostatic equilibrium is the balance between gravity pulling inward and pressure from the hot interior pushing outward.

What is plasma, and what is the Sun’s interior made of?

Plasma is gas so hot that atoms separate into charged particles. The Sun’s interior is plasma, not solid material.

How does energy move through the Sun’s radiative zone?

In the radiative zone, energy moves outward mainly through photons that are repeatedly absorbed, re-emitted, or scattered by matter.

How does nuclear fusion differ from chemical burning?

Fusion changes atomic nuclei and releases energy; unlike chemical burning, it is not an ordinary chemical reaction.

What kind of star is the Sun, and what powers it?

The Sun is a G2 V main-sequence star, a long-lived phase in which hydrogen fusion in its core supplies its energy.

How can a star respond when its interior pressure falls?

When pressure falls, gravity compresses the star. Compression heats the core, which can increase fusion and help restore balance.

What does energy balance mean for a star?

A star’s energy balance means energy produced inside eventually flows outward and radiates into space.

What happens in the Sun’s core?

The core is the Sun’s hottest, densest region, where most of its energy is produced by fusion. Its temperature is roughly 15 million °C.

How does the convective zone transport energy?

In the convective zone, hot plasma rises and cooler material sinks, carrying energy in large circulating currents.

What is the Sun’s photosphere?

The photosphere is the visible layer from which most sunlight escapes. It is often called the Sun’s surface, but it is not solid.

Why is fusion between hydrogen nuclei in the Sun rare?

In the Sun, positively charged protons repel one another, making fusion rare. Quantum effects allow some to get close enough for the strong nuclear force to bind them.

What is the simplified net result of the Sun’s proton–proton chain?

In simplified net form, four hydrogen nuclei become one helium-4 nucleus, with energy, two neutrinos, and positrons produced along the way.