Download Lives of stars

Chapter 19
By reading this chapter, you will learn
19-1 How a main-sequence
star changes as it converts
hydrogen to helium
19-2 What happens to a star
when it runs out of hydrogen
fuel
19-3 How aging stars can
initiate a second stage of
thermonuclear fusion
19-4 How H-R diagrams for
star clusters reveal the later
stages in the evolution of
stars
19-5 The two kinds of stellar
populations and their
significance
19-6 Why some aging stars
pulsate and vary in luminosity
19-7 How stars in a binary
system can evolve very
differently from single,
isolated stars
Red Giants
The lives of the sun
1. Explain what will happen to the sun in the
future. (a- the sun will be stable for another few
billion years, b- sun will gradually get larger and
will become a red giant, c- sun have started its
He fusion already, d- sun will start the new set
of fusion after it expand.
2. T/F: Larger star will have more mass to burn, so
it will last for a long time.
3. During the first red giant stage: a- shell
hydrogen fusion is common, b- shell helium
fusion is common, c- Fe fusion at core is
common, d- Helium fission is common
1. a,b,&d, 2. F, 3. a
Click on “enter” to review your answers:
Post main sequence stars
cluster’s age
Variable stars
Cepheid variable
Its change in apparent magnitude match the expansion and contract of the star surface.
A
B
To review the lives of the stars, work on the
Stellar Evolution worksheet (part of your
homework this week!)
Lum
E
(Lsun)
The letters A-F represent stars
1. This diagram is a plot of temperature vs. luminosity. What do we call this
C
D
diagram?
2. Which two stars have same temperature?
Temperature
3. Do these pair(s) of stars have same stellar classification? explain
4. Which two stars have same luminosity?
5. Do these pair(s) have same stellar classifications? explain
6. Which letter is most similar to the current sun’s location n the diagram?
7. When the sun starts to die, the sun will start to expand. The sun will be
larger, hence brighter, but it till be lower temperature. Which letter represents
this state of the sun? What do call this type of star?
8. After the dieing process the sun starts, sun will be variable star for short
period of time. The sun will change its luminosity as series of shell fusion
takes place. Which letter represents this state of the sun? What do call this
type of star?
9. When the sun completely die, the sun will have exposed core, hence the
temperature will be higher, but it sill be very small (about size of the earth) so
it will not emit as much light. Which letter represents this state of the sun?
What do call this type of star?
10.Which letters are in its hydrostatic equilibrium or main sequence?
11.Which of the main sequence stars have longer life expectancy? Why?
Mid life crisis of the stars!
1. As the star starts to die, it starts to pulsate. This
happens when the star is in: a- main sequence,
b- instability strip, c- white dwarf stage, d- this
could happen at any place on HR diagram
2. To determine the age of relatively old star cluster,
you would look for: a- by counting the number of
stars., b- Largest main sequence star, c- by
finding variable stars, d- smallest star in the main
sequence.
3. Which type of variable star is brighter for its
mass? a- Lyra variable, b- metal poor Cepheid
variable, c- metal rich Cepheid variable, d- the
stars still in main sequence
Close binary star systems
Semidetached
binary
Detached
binary
Contact binary
Over contact binary
Mass transfer in a close binary system occurs when
one star in a close binary overflows its Roche lobe
The other type of varying
brightness: binary system
1. How close the binary stars needs to be for any
type of mass transfer to take place? Adetached, b-semi-detached, c- contact, dover contact.
2. In Which type of binary the atmospheric
composition will be identical. A- detached, bsemi-detached, c- contact, d- over contact.
3. T / F: the initial mass of the star is the only
condition that determines how long the star
will live.