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Transcript
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.