Abstract
We have so far covered topics that describe how a star forms, how the mass of stars can be determined by observing binary-star systems, and how long it takes to become a star. Now we shall discuss how long a star will remain on the main sequence and then look at what happens due to changes in its internal structure.
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Notes
- 1.
Remember that all elements other that hydrogen and helium are called metals by astronomers.
- 2.
We shall discuss this remarkable fact in later sections.
- 3.
See the next section for a discussion on red giant stars.
- 4.
Asymptotic Giant Branch.
- 5.
Recall that for hydrogen burning to start, the temperature has to reach about 10 million K, whereas for helium burning, the temperature has to achieve a staggering 100 million K.
- 6.
If you are a particle physicist!
- 7.
The time for a star to complete one cycle in its brightness variation is called its period. Thus, for δ Cephei, its period is 5.5 days.
- 8.
Population I stars are bright supergiant main sequence stars with high luminosity, such as O- and B-type stars, and members of young open star clusters. Molecular clouds are often found in the same location as Population I stars. They are usually in the disk of a galaxy and concentrated in the spiral arms, following nearly, but not always, circular orbits. Population I stars include stars with a range of ages, maybe 10 billion years old, or 1 year old. Population II stars, on the other hand, are usually old stars. Examples include RR Lyrae stars and the central stars of planetary nebulae. This type of star has no correlation with the location of the spiral arms. They are also found in globular clusters, which are almost entirely in the halo and central bulge of the galaxy. Therefore, they represent the oldest stars, which formed very early in the history of the galaxy.
- 9.
A list of organizations is in the appendices in this book.
- 10.
There is some doubt about this, again due to its high galactic latitude.
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Inglis, M. (2015). Life on the Main Sequence. In: Astrophysics Is Easy!. The Patrick Moore Practical Astronomy Series. Springer, Cham. https://doi.org/10.1007/978-3-319-11644-0_10
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