The Sun and the life cycle of a star
Watch the whole lecture free
Make a free account to watch every lecture to the end: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
That was the teaching part. The rest of this lecture is free with an account: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
No password needed now: we email you a link to set one. Already have an account? Sign in, then come back to this page.
The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- We are made of stardust
- The Sun
- What powers the Sun
Read the transcript of the teaching part
Last time
Before we start: last time, in Galaxies, light-years and redshift, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
We are made of stardust
The iron in your blood, the calcium in your bones, the oxygen in your lungs. Every atom heavier than hydrogen and helium was made inside a star, and flung into space when the star died. To see how, we need the story of the Sun, and then the life of a star from birth to death.
The Sun
The Sun is a star: a huge ball of very hot gas, mostly hydrogen and helium. It is about 110 times wider than the Earth. Its core is about 15 million degrees Celsius. Its surface is about 5500 degrees. It radiates most of its energy as infrared, visible light and ultraviolet.
What powers the Sun
In the core, the temperature and pressure are so great that hydrogen nuclei fuse together to make helium. This nuclear fusion releases enormous energy. The Sun turns about 4 million tonnes of mass into energy every second. Light takes about 500 seconds to reach the Earth.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: The life cycle of stars · The Sun as a star · The life cycle of a star · The Sun as a star.
The whole chapter: Stars and the Universe, Stars and the Universe.
6.1–6.2 Earth, stars and the Universe
- Gravitational fields, orbits and planetary data 6 min
- Galaxies, light-years and redshift 5 min
- The Sun and the life cycle of a star 5 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.