AstronomyLesson 2 of 3 in the course Stars from Adolescence to Old Age

Star Clusters: Stellar Evolution, Types, and Galactic Distribution

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Star clusters allow astronomers to investigate stellar evolution even though individual stars change too slowly for us to watch a complete life cycle directly. Because cluster members formed under similar conditions, their differences help reveal how stellar mass affects the pace of evolution.

A star can take millions or billions of years to pass through important stages of its life. No human observer can watch one star complete its main-sequence lifetime and evolve into a red giant. Astronomers can instead compare many stars in a cluster.

All flashcards

What is a star cluster?
A group of stars close together in space and held together by gravity.
What does an H–R diagram compare?
Stars’ luminosities and surface temperatures.
What are typical features of globular clusters?
They are ancient, nearly spherical, densely populated systems found mainly in the Galactic halo and central bulge.
Why do open clusters often disperse?
Stars can escape through their motions or close encounters; giant molecular clouds can also disrupt the cluster.
What can O-type stars indicate about a stellar association?
Their short lifetimes suggest that star formation in the region happened recently.

Quiz questions

  1. Why do more massive stars generally reach later evolutionary stages sooner than lower-mass stars?Answer: They use their fuel more rapidly.
  2. Which description best distinguishes a stellar association from an open cluster?Answer: It is much more extended and typically very young.
  3. Why does finding O-type stars in a stellar association suggest recent star formation?Answer: O-type stars have lifetimes of only about a million years.
  4. Which event can gravitationally disturb and tear apart an open cluster?Answer: A close encounter with a giant molecular cloud.
  5. Where are globular clusters found mainly in the Milky Way?Answer: In the Galactic halo and central bulge.

Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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