What you’ll learn7 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—E.5.1—Stellar equilibrium• Stars are stable when outward radiation pressure balances inward gravity.Syllabus objective—E.5.2—Fusion in stars• Fusion is a source of energy in stars.Syllabus objective—E.5.3—Fusion conditions• Fusion in stars requires high density and temperature.Syllabus objective—E.5.4—Stellar mass and evolution• Stellar mass determines star evolution pathway.Syllabus objective—E.5.5—HR diagram regions• Use HR diagram regions to describe star properties.• Include main sequence, red giants/supergiants, white dwarfs and lines of constant radius.Syllabus objective—E.5.6—Stellar parallax• Stellar parallax distance: d(pc)=1/p(arcsec).Syllabus objective—E.5.7—Stellar radii• Determine stellar radius from luminosity and surface temperature.Syllabus objective