extra credit! get out your clickers. the following questions are worth 2 points each
TRANSCRIPT
![Page 1: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/1.jpg)
Extra credit!
Get out your clickers.
The following questions are worth 2 points each.
![Page 2: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/2.jpg)
What direction does the Sun rise in Sydney?
A. In the East
B. In the West
C. In the North
D. In the South
E. Cannot conclude
![Page 3: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/3.jpg)
Looking south in Sydney, what type of stars would you see?
A. Seasonal
B. Circumpolar
C. Neither
![Page 4: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/4.jpg)
Looking North in Sydney, what type of stars would you see?
A. Seasonal
B. Circumpolar
C. neither
![Page 5: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/5.jpg)
Sydney’s circumpolar stars rotate
A. Counterclockwise
B. Clockwise
C. Rise in east, set in west
D. Rise in west, set in east
![Page 6: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/6.jpg)
Agenda
Reading: Finish Unit 5, if you haven’t already.
Star clusters Stellar life cycles (stellar evolution)
![Page 7: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/7.jpg)
Star clusters
Easier to observe overall evolution than of one star
Stars in a cluster Formed at the same time Have similar composition They will differ only in mass
![Page 8: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/8.jpg)
Globular clusterM 15
NASA
Thousands to millionsof stars
![Page 9: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/9.jpg)
Globular cluster Tucanae 47
NASA
![Page 10: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/10.jpg)
Open cluster: Pleiades
Hundreds of stars
Case Western
![Page 11: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/11.jpg)
Open Cluster: Jewel box
Jordell Observatory
![Page 12: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/12.jpg)
HR diagram of a cluster
Color (B – V) on horizontal axis Equivalent to
OBAFGKM Apparent magnitude
(V) on vertical axis All stars at the same
distance Easy to convert to
absolute magnitude
![Page 13: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/13.jpg)
Evolution and the HR diagram
High mass (higher luminosity) stars progress through life more quickly
Lower mass stars take longer to be born, consume their fuel more slowly.
![Page 14: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/14.jpg)
Which HR diagram shows the older cluster?
A. B.
C. Cannot conclude
![Page 15: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/15.jpg)
Young cluster ~80 million yrs
U. of Sheffield
![Page 16: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/16.jpg)
Older cluster
U. of Oregon
![Page 17: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/17.jpg)
Compare the HR diagrams
Many older red giantsMany young, hot (blue) stars
![Page 18: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/18.jpg)
Star clusters — summary
Stars in one cluster are of different types but the same age.
Observing many clusters tells us about star life cycles HR diagram Old stars leave the main sequence Cluster age <=> turnoff point
![Page 19: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/19.jpg)
Stellar “evolution” (first part)
What we found in star clusters: Small stars live longer Very massive stars live hard and die
young Old stars leave the main sequence to
become red giants.
![Page 20: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/20.jpg)
Raw materials for star birth
Interstellar clouds.
This is a star cluster in the making!
![Page 21: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/21.jpg)
Raw materials for star birth
![Page 22: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/22.jpg)
In a Stellar nursery
Raw materials collapse Protostar begins to spin Eventually, fusion of H into He begins
![Page 23: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/23.jpg)
Life as a star
Zero-age main sequence when a star first starts fusing H into He
Stars do this for 90% of their lives
![Page 24: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/24.jpg)
Big stars don’t live long!
Massive stars burn very fast.
They soon run out of fuel!
Wikipedia
![Page 25: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/25.jpg)
Time on main sequence versus initial stellar mass
0.4 0.8 1.1 1.7 3.3 16 40
Large stars live and die very quickly!200 billion years!
Initial stellar mass (MSun)
~12 billion years (Sun)
50 million years
1 million years!
![Page 26: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/26.jpg)
He core contracting
H fusing
Exterior expanding
H runs out: star becomes a red giant
This is how starsleave the main sequence!
![Page 27: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/27.jpg)
Wikipedia
Our star is tiny comparedto a red giant!
![Page 28: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/28.jpg)
Further evolution
Helium all used up, gravity takes over again
Much mass is spewed into space
![Page 29: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/29.jpg)
Mass now determines death
Low mass: White dwarf Medium mass: Neutron star or pulsar High mass: Black hole
![Page 30: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/30.jpg)
Summary
Stars are born from Hydrogen Stars spend 90% of their lifetime
fusing Hydrogen into Helium Stars leave the main sequence and
become red giants
![Page 31: Extra credit! Get out your clickers. The following questions are worth 2 points each](https://reader030.vdocuments.us/reader030/viewer/2022032722/56649ce35503460f949af13e/html5/thumbnails/31.jpg)
Next time
Death of stars:
Black holes, neutron stars, Relativity