What you’ll learn2 learning objectivesChoose one objective for a focused lesson, or study the complete topic.6.2.1.1Sun is a star of medium size• Know: the Sun is a star of medium size, consisting mostly of hydrogen and helium, and that it radiates most of its energy in the infrared, visible light and ultraviolet regions of the electromagnetic spectrumSyllabus objective6.2.1.2Stars are powered by nuclear reactions• Know: stars are powered by nuclear reactions that release energy and that in stable stars the nuclear reactions involve the fusion of hydrogen into heliumSyllabus objective