Zero-age main sequence

Definition

Zero-age main sequence (ZAMS) is the stage in a star's life when it first begins to fuse hydrogen into helium in its core. At this point, the star is fully formed and has settled into a stable phase of nuclear fusion.

5 Must Know Facts For Your Next Test

1. Stars on the zero-age main sequence are at their most stable and have just begun hydrogen fusion.
2. The position of a star on the ZAMS is determined by its mass.
3. Stars remain on the ZAMS for a significant portion of their lifetimes, depending on their mass.
4. The temperature and luminosity of a ZAMS star are directly related to its mass.
5. A star moves off the ZAMS once it exhausts the hydrogen in its core and starts fusing heavier elements.

Review Questions

• What process marks the beginning of a star's life on the zero-age main sequence?
• How does a star's mass affect its position on the zero-age main sequence?
• What happens to a star after it leaves the zero-age main sequence?

Related terms

Main Sequence Star:

A star that is currently fusing hydrogen into helium in its core, positioned along the Main Sequence on an H-R diagram.

Red Giant:

A later evolutionary phase of a star where it expands and cools after exhausting hydrogen in its core.

Hertzsprung-Russell Diagram: A graphical representation of stars showing the relationship between their luminosities and temperatures.