CHAPTER 26 Study Guide

26.1 The Sun

Key Concepts

• The sun's energy is produced in its core by fusion.

• The sun remains stable because the inward pull of gravity balances the outward pressure from fusion.

• The sun's interior consists of the core, radiation zone, and convection zone. Layers of the sun's atmosphere are the photosphere, chromosphere, and corona.

• Features of the sun's atmosphere include sunspots, prominences, and solar flares.

Vocabulary

core, p. 830; radiation zone, p. 830; convection zone, p. 831; photosphere, p. 831; chromosphere, p. 831; corona, p. 831; solar wind, p. 831; sunspots, p. 832; prominences, p. 833; solar flare, p. 833

26.2 Stars

Key Concepts

• Astronomers measure the parallax of nearby stars to determine their distance from Earth.

• Astronomers use several properties to classify stars.

• Most stars have a composition similar to the sun.

• H-R diagrams are used to estimate the sizes and distances of stars and to infer how stars change.

Vocabulary

star, p. 834; light-year, p. 834; parallax, p. 835; apparent brightness, p. 836; absolute brightness, p. 837; absorption lines, p. 837; H-R diagram, p. 838; main sequence, p. 839; supergiants, p. 839; giants, p. 839; white dwarf, p. 839

26.3 Life Cycles of Stars

Key Concepts

• A star is formed when nuclear fusion begins.

• A star's mass determines the star's place on the main sequence and how long it will stay there.

• A star ends up as a white dwarf, neutron star, or black hole once it exhausts its fuel supply.

Vocabulary

nebula, p. 840; protostar, p. 841; planetary nebula, p. 842; supernova, p. 843; neutron star, p. 844; pulsar, p. 844; black hole, p. 844

26.4 Groups of Stars

Key Concepts

• • Astronomers have determined that more than half of all stars are members of star systems.

• • There are three basic kinds of star clusters: open clusters, associations, and globular clusters.

• • Astronomers classify galaxies into four main types: spiral, barred-spiral, elliptical, and irregular.

Vocabulary

constellation, p. 846; star system, p. 847; binary star, p. 847; globular cluster, p. 847; galaxy, p. 848; spiral galaxies, p. 848; barred-spiral galaxies, p. 848; elliptical galaxies, p. 848; irregular galaxies, p. 848; quasars, p. 849

26.5 The Expanding Universe

Key Concepts

• The observed red shift in the spectra of galaxies shows that the universe is expanding.

• Astronomers theorize that the universe came into being in an event called the big bang.

• Dark matter can only be detected by observing its gravitational effects on visible matter.

Vocabulary

red shift, p. 852; Hubble's Law, p. 853; big bang theory, p. 854; dark matter, p. 855

Thinking Visually

Comparing and Contrasting Use information from the chapter to complete the table below.

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