stellar properties - college of arts and sciences
TRANSCRIPT
![Page 1: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/1.jpg)
Stellar Propertiesl positions and velocities – astrometryl luminosities
- inverse-square lawl 𝑓 = #
$%&'
- filters – photometryl 𝑓( = ∫𝑓 𝜆 𝑡( 𝜆 𝑑𝜆
- the magnitude scalel 𝑚. −𝑚0 = −2.5 log.7
898'
= 2.5 log.78'89
l 𝑚 −𝑀 = 5 log.7 𝐷(pc) − 5
- colors
l 𝑈 − 𝑉 ≡ 𝑚C −𝑚D = 2.5 log.78E8F
, etc.
![Page 2: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/2.jpg)
Some MagnitudesSun: 𝑚D = −26.7, 𝐷 = 1 𝐴𝑈 ⟹ 𝑀D = 4.8 → 𝐿⨀
⍺ Centauri AB: 𝑚D = −0.27, 𝐷 = 1.37 pc ⟹ 𝑀D = 4.1 1.9 𝐿⨀⍺ Centauri A: 𝑚D = 0.01, 𝐷 = 1.37 pc ⟹ 𝑀D = 4.4 1.4 𝐿⨀⍺ Centauri B: 𝑚D = 1.33, 𝐷 = 1.37 pc ⟹ 𝑀D = 5.7 0.4 𝐿⨀
Sirius A: 𝑚D = −1.47, 𝐷 = 2.6 pc ⟹ 𝑀D = 1.4 23 𝐿⨀Sirius B: 𝑚D = 8.44, 𝐷 = 2.6 pc ⟹ 𝑀D = 11.4 2.3×10WX 𝐿⨀⍺ Orionis: 𝑚D = 0.5, 𝐷 = 222 pc ⟹ 𝑀D = −6.2 2.5×10$ 𝐿⨀
M87: 𝑚D = 9.6, 𝐷 = 16 Mpc ⟹ 𝑀D = −21.4 3.0×10.7 𝐿⨀3C273: 𝑚D = 12.9, 𝐷 = 750 Mpc ⟹ 𝑀D = −26.5 3.3×10.0 𝐿⨀
![Page 3: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/3.jpg)
Stellar Propertiesl positions and velocities – astrometryl luminositiesl temperatures
- “effective” blackbody temperature- colors - spectra
l compositionl radiil masses
Z'Z9= ['
[9𝑒W]^9'/`a (Boltzmann))
![Page 4: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/4.jpg)
![Page 5: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/5.jpg)
41,000 K
9,100 K
5,800 K
5,200 K
3,300 K
![Page 6: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/6.jpg)
![Page 7: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/7.jpg)
Spectral Type Surface Temperature Distinguishing Features
O > 25,000K H; HeI; HeII
B 10,000-25,000K H; HeI; HeII absent
A 7,500-10,000K H; CaII; HeI and HeII absent
F 6,000-7,500K H; metals (CaII, Fe, etc)
G 5,000-6,000K H; metals; some molecular species
K 3,500-5,000K metals; some molecular species
M < 3,500K metals; molecular species (TiO!)
C < 3,500K metals; molecular species (C2!)
![Page 8: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/8.jpg)
![Page 9: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/9.jpg)
Stellar Propertiesl positions and velocities – astrometryl luminositiesl temperaturesl composition
![Page 10: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/10.jpg)
![Page 11: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/11.jpg)
Stellar Propertiesl positions and velocities – astrometryl luminositiesl temperaturesl compositionl radii
- direct measurement: 𝑅 = 𝐷 Δ𝜃- radiation laws: 𝐿 = 4𝜋𝑅0 𝜎𝑇$
- red giants and white dwarfs
![Page 12: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/12.jpg)
Stellar RadiiSun at 10 pc: 𝑅⨀ = 10 pc Δ𝜃 ⟹ Δ𝜃 = 4.6 × 10W$ arcsec𝛼 Ori at 200 pc: 4 AU = 200 pc Δ𝜃 ⟹ Δ𝜃 = 0.02 arcsec
𝐿 = 4𝜋𝑅0 𝜎𝑇$ , 𝐿⨀ = 4𝜋𝑅⨀0 𝜎𝑇⨀$
⟹ ##⨀= i
i⨀
0 aa⨀
$⟹ i
i⨀= #
#⨀
9' a
a⨀
W0
𝐿 = 10X𝐿⨀, 𝑇 = 3000 𝐾 ⟹ 𝑅 = 126 𝑅⨀ = 0.6 AU RED GIANT𝐿 = 10WX𝐿⨀, 𝑇 = 10$ 𝐾 ⟹ 𝑅 = 0.011 𝑅⨀ = 1.2 𝑅⨁ WHITE DWARF
![Page 13: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/13.jpg)
Stellar Propertiesl positions and velocities – astrometryl luminositiesl temperaturesl compositionl radiil masses
- need dynamics- binary stars
![Page 14: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/14.jpg)
Early-Release Image of Omega Centauri, taken by WFC3/UVIS on board the Hubble Space Telescope
(HST)
http://hubblesite.org/gallery/wallpaper/pr2009025q/
![Page 15: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/15.jpg)
A close-up of the central region. This image was made by combining separate red, green, and
blue images
![Page 16: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/16.jpg)
The red image is from filter F814W, which sees only very red light.
![Page 17: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/17.jpg)
The green image is from filter F336W, which sees only blue light.
![Page 18: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/18.jpg)
The blue image is from filter F225W, which sees only ultraviolet light.
![Page 19: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/19.jpg)
Let’s sort the stars by color, putting the bluestars on the left and the red stars on the right.
![Page 20: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/20.jpg)
Note that most stars are nearly white.
![Page 21: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/21.jpg)
Astronomers also characterize stars in terms of brightness.
![Page 22: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/22.jpg)
Let’s sort the stars, putting the brightstars on top and the faint stars on the
bottom.
![Page 23: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/23.jpg)
This is called a Hertzsprung-Russel(H-R) Diagram.
![Page 24: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/24.jpg)
The unmistakable order in diagrams like this led astronomers to develop theories
to explain stellar evolution.
temperature
luminosity
![Page 25: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/25.jpg)
MS
SGB
RGBHB
WD
Stars lie along a few well-defined sequences.
![Page 26: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/26.jpg)
The vast majority of stars lie along the Main Sequence (MS)
MS
![Page 27: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/27.jpg)
![Page 28: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/28.jpg)
![Page 29: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/29.jpg)
![Page 30: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/30.jpg)
![Page 31: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/31.jpg)
![Page 32: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/32.jpg)
Stellar Properties
l positions and velocitiesl luminosities 10W$ − 10$ 𝐿⨀l temperatures 3000 − 30000 Kl composition 0.001 − 10 solarl radii 0.1 − 20 𝑅⨀ at birth
WD: 10$ km; RG: >1 AUl masses 0.1 − 100 𝑀⨀ at birth
![Page 33: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/33.jpg)
𝑅 ~𝑀7.n
stellar lifetime ~ 𝑀/𝐿 ~ 𝑀WX
L ~𝑀$
![Page 34: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/34.jpg)
Key Nuclear reactions – Main Sequence
lProton-proton chain
l11H + 11H ® 2
2He ® 21H + e+ + ne
l21H + 11H ® 3
2He
l32He + 32He ® 4
2He + 2 (11H)
l4 (11H) ® 4
2He +2 e+ + 2ne+ 24 MeV
![Page 35: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/35.jpg)
Key Nuclear reactions – Main Sequence
lCNO cycle
l12
6C + 11H ® 137N + g
l13
7N ® 136C + e+ + ne
l13
6C + 11H ® 147N + g
l14
7N + 11H ® 158O + g
l15
8O ® 157N + e+ + ne
l15
7N + 11H ® 126C + 42He
l4 (11H) ® 4
2He +2 e+ + 2ne+ 24 MeV
![Page 36: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/36.jpg)
Key Nuclear reactions – Post-Main-Sequence
lTriple-alpha process
l42He + 42He ® 8
4Be – 94 keV
l84Be + 42He ® 12
6Be + 7.4 MeV
lAlpha capture
126C + 42He ® 16
8O + 7.2 MeV
168O + 42He ® 20
10Ne + 4.7 MeV
2010Ne + 42He ® 24
12Mg + 9.3 MeV
etc.
![Page 37: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/37.jpg)
Z = M(>He) / M(total)
𝑡op ~𝑀𝐿
~ 𝑀WX
~ 10.7 yr𝑀𝑀⨀
WX
![Page 38: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/38.jpg)
![Page 39: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/39.jpg)
![Page 40: Stellar Properties - College of Arts and Sciences](https://reader030.vdocuments.us/reader030/viewer/2022012701/61a3b2b3bd2178620b00212a/html5/thumbnails/40.jpg)
Endpoints of Stellar Evolution
l < 0.08 M¤ brown dwarf (degenerate H)
l 0.08−0.25 M¤ He white dwarf
l 0.25−8 M¤ CO white dwarf t ~ 1010 yr (M/M¤)-3
l 8−12 M¤ NeO white dwarf
l 12−20 M¤ supernova/neutron star t ~ 3-20 × 106 yr
l >20 M¤ supernova/black hole