Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgements
- 1 Watchers of the skies
- 2 Our Sun
- 3 Aspects of our Solar System
- 4 The rocky planets
- 5 The hunt for Planet X
- 6 Voyages to the outer planets
- 7 Harbingers of doom
- 8 Impact!
- 9 Four hundred years of the telescope
- 10 The family of stars
- 11 Aging stars
- 12 The search for other worlds
- 13 Are we alone? The search for life beyond the Earth
- 14 Our island Universe
- 15 Wonders of the southern sky
- 16 Proving Einstein right
- 17 Black holes: no need to be afraid
- 18 It’s about time
- 19 Hubble’s heritage: the astronomer and the telescope that honours his name
- 20 The violent Universe
- 21 The invisible Universe: dark matter and dark energy
- 22 The afterglow of creation
- 23 To infinity and beyond: a view of the cosmos
- Index
- Plate section
- References
11 - Aging stars
Published online by Cambridge University Press: 05 October 2014
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgements
- 1 Watchers of the skies
- 2 Our Sun
- 3 Aspects of our Solar System
- 4 The rocky planets
- 5 The hunt for Planet X
- 6 Voyages to the outer planets
- 7 Harbingers of doom
- 8 Impact!
- 9 Four hundred years of the telescope
- 10 The family of stars
- 11 Aging stars
- 12 The search for other worlds
- 13 Are we alone? The search for life beyond the Earth
- 14 Our island Universe
- 15 Wonders of the southern sky
- 16 Proving Einstein right
- 17 Black holes: no need to be afraid
- 18 It’s about time
- 19 Hubble’s heritage: the astronomer and the telescope that honours his name
- 20 The violent Universe
- 21 The invisible Universe: dark matter and dark energy
- 22 The afterglow of creation
- 23 To infinity and beyond: a view of the cosmos
- Index
- Plate section
- References
Summary
This chapter will look at how stars evolve during the later stages of their lives, and describe the remnants left when they die: white dwarfs, neutron stars and black holes.
For a collapsing mass of gas to become a star, nuclear fusion has to initiate in its core. This requires a temperature of ~10 million K and this can only be reached when the contracting mass is greater than about 1029 kg, about 1/20 the mass of the Sun, or 20 times that of Jupiter.
In low-mass stars, less than ~0.5 solar masses, the conversion of hydrogen to helium by nuclear fusion is the same as in our Sun. However, whereas in stars of greater mass nuclear fusion only converts ~10% of the mass of the star (that residing in its core), in the lowest mass stars it is thought that convection currents mix the star’s interior and so will allow much of the star’s mass to undergo nuclear fusion, so increasing the time during which they can carry out the fusion of hydrogen to helium – a period that is significantly longer than the present age of the Universe. We thus have no direct observational evidence of what happens when fusion ceases in such stars and can only use computer modelling to investigate what might happen.
- Type
- Chapter
- Information
- A Journey through the UniverseGresham Lectures on Astronomy, pp. 145 - 163Publisher: Cambridge University PressPrint publication year: 2014