Download Redshift - Old Age and Red Giants

RedShift: “Old Age and Red Giants”
Astronomy
Name:
This Redshift begins on page 235.
Period:
23.1
a. Summary of information on pages 8-19
Gravity squeezes matter inside the sun so much that temperatures are great enough (10,000,000)
to fuse hydrogen into helium, while release neutrinos and gamma rays. A star’s luminosity directly
depends on its core temperature
b. Summary of information on pages 22-29
Stars like the Sun are in hydrostatic equilibrium, balancing the inward pull of gravity with the
outward push of nuclear reactions (fusion). The rate of fusion is related to the diameter of a star.
If a star gets larger, the rate of reactions lessens, and gravity pulls inward to decrease its size.
23.2, 23.3, 23.4
DO NOT PLOT ON GRAPH, BUT FILL IN TABLE
Star Name Spectral
Type
Sun
G2 V
Sirius A
A1 V
Canopus
F0 I
Arcturus
K2 III
Rigel
G2 V
Kentaurus
Vega
A0 V
Capella
G8 III
Rigel
B8 I
Procyon
F5 IV
Achernar B3 V
Luminosity
Sun = 1
1
2 x 101
1 x 103
1 x 102
1.5
5 x 101
2 x 102
8 x 104
9
5 x 102
Brightest Stars in the Sky
Type of Star Name Spectral
Star
Type
Main S.
Betelgeuse M2 I
Main S.
Agena
B1 III
Yellow G. Altair
A7 IV
Orange
Aldebaran K5 III
Main S.
Spica
B1 V
Main S.
Yel. G
Blue S.G.
Main S.
Main S.
Antares
Fomalhaut
Pollux
Deneb
M1 I
A3 V
K0 III
A2 I
Luminosity
Sun = 1
1 x 105
9 x 103
1 x 101
2 x 102
6 x 103
Type of
Star
Red S.G.
Blue G.
Main S.
Orange G.
Main S.
1 x 104
5 x 101
6 x 101
8 x 104
Red S.G.
Main S.
Orange G.
White S.G.
23.5
Q1. (only answer question portion)
Canopus, Rigel, Betelgeuse, Antares are type I supergiants.
Q2. (only answer question portion)
Rigel, Betelgeuse, Antares, Deneb are type II bright giants.
Q3. (only answer question portion)
Arcturus, Capella, Agena, Aldebaran, Pollux are type III giants
Q4.
Canopus, Arcturus, Capella, Rigel, Betelgeuse, Agena, Aldebaran, Antares, Pollux, Deneb are all
significantly off the main sequence.
23.6
Summary of information on pages 16-20
Red giants (and supergiants) have cooler outer “shells”, as energy from the core is spread into a
larger volume, but have a hot helium center. They are “two stars in one”.
23.7
Q5.
Giants and Supergiants: Rigel, Deneb, Canopus
Q6.
Betelgeuse and Antares are both large red stars with short remaining lifetimes.
Q7.
Large red stars are cooling and near the end of their lifetimes.
Q8.
Antares is an M1 I star and will likely turn into an M2 I star like Betelgeuse.
Q9.
Deneb (A2 I) and Canopus (F0 I) will likely turn into an M I star like Antares.
Q10.
The surface area of the red giants is greater, so the energy is distributed more and the star is
cooler. But the core is highly compressed where helium is made.
Q11.
Aldebaran (K5 III) and Pollux (K0 III) are orange giants that will cool into red giants like the sun.
23.8 (OMIT THIS SECTION)
Q12.
Q13.
Q14.
Q15.
Q16.
Conclusion
Describe what you learned about the path a star takes after it moves off the main sequence.
The path is complex and depends on the star’s mass. Different stars that are more or less massive than the sub take
very different paths and end their stellar lives in different ways.
Describe how you can tell if a star is still burning hydrogen in its core or if its core has begun to fuse other elements.
If a star has begun fusing other elements it will grow in size, change density, fluctuate in temperature, etc. If it is still
buring hydrogen, it is still living on the main sequence.
Describe how you can look at a non-main-sequence star and guess what kind of star it was before it left the main sequence.
The luminosity of a post-main-sequence star stays nearly constant. That is, the star moves mostly across the HR
diagram, from left to right, getting cooler but maintaining intrinsic brightness (luminosity).
Tell how you can predict what kind of a star a main-sequence star will be come when it runs out of hydrogen.
The mass of a star determines its post-main-sequence path through the HR diagram.
Tell why a star does not change much in brightness as it runs out of fuel.
As a star leaves the main sequence it expands in size and cools in temperature. Overall, it stays
about the same brightness, like a light bulb changing from blue to red while also getting larger,
the bulb will maintain about the same brightness.