2 Stars and Stellar Evolution Free Online FlashCards

Where do stars form?

Stars form in cold, dense molecular clouds made of gas and dust.

What is hydrostatic equilibrium in a star?

Hydrostatic equilibrium is the balance between inward gravity and outward pressure from hot gas and energy flowing through the star.

How does greater stellar mass affect a star’s lifetime?

More massive stars need greater core energy to resist gravity, so they consume fuel faster and generally have shorter lives.

What can a star’s spectrum reveal?

A star’s spectrum can reveal its temperature and the elements in its outer layers.

How does a star change after its core hydrogen is depleted?

When core hydrogen is depleted, fusion slows and the core contracts. The star’s outer layers respond by expanding into a giant or, if it is massive, a supergiant.

What heavier elements can a Sun-like star make by fusing helium?

A star like the Sun can fuse helium into heavier nuclei, including carbon and oxygen, but cannot sustain the full sequence of fusion reactions found in the most massive stars.

What supports a white dwarf against further collapse?

A white dwarf is a compact stellar core supported against further collapse by electron degeneracy pressure.

Why can iron fusion lead to core collapse in a massive star?

In the most massive stars, fusion can build elements up to iron. Fusing iron does not provide the energy needed to support the core.

How do stars contribute material to later generations of stars and planets?

Fusion and stellar winds or explosive deaths return elements to space. This enriched material can later become part of new stars, planets, and other objects.

How does a collapsing cloud clump become a protostar?

Gravity pulls a clump of cloud material inward. As it contracts and gathers matter, it heats up and becomes a protostar.

What marks the start of a star?

A protostar becomes a star when its core gets hot and dense enough for hydrogen nuclei to fuse into helium.

What happens during a star’s main-sequence stage?

The main sequence is the stage when a star fuses hydrogen into helium in its core. Stars spend most of their lives in this stage.