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郭苗
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1 老老年 (interstellar medium) ~10 19 molecules/cm 3 ~1/cm 3 (dark molecular clouds) 度 cc 數度 ~10 K 零 260 度來 --- (interstellar reddening) As light from a distant object travels through interstellar space Distant object short-wavelength blue light is scattered or absorbed by dust grains Dust grains while red light passes through more readily Observer Dust causes interstellar reddening. 1

2 B33 (NOAO) 2 (emission nebula) Balmer alpha (reflection nebula) 藍 (dark nebula) Star Shadows Remote Observatory (dense core) 理

3 參 Dense cores 度力度力 Jeans instability (protostar) 見獵 by Spitzer Space Telescope 行見度 L1014 見 3

4 (M16) H I H II OB star H I H II 離離 OB 離離 H II region H II regions outline a spiral galaxy (spiral arms) (giant molecular clouds, GMCs) 量 OB 年量 OB OB association (OB 烈烈輻不 A tour in the Orion molecular cloud 4

5 (brown dwarfs) Stars form by accreting surrounding material. 累量 stellar winds, outflows, jets) 量流 (mass loss) 獵 Credit: G. Schneider (UofA), K. L. Luhman (CfA), et al., NICMOS IDT, NASA WFPC2 data: C. O'Dell and S. Wong (Rice) Mass loss from massive stars Circumstellar accretion disk Protostar hidden by dark, dusty nebula jet jet 易力螺狀兩流 (jets) 1000 AU 5

度行量輻流輻量力 Protostar hidden by dark, dusty nebula 力量 X 例 4

Reaction 1 H + 1 H 2 H + e + + e e + + e 2 + 1.

49 MeV 3 He + 3 He 4 He + 1 H + 1 H + 12.

takes about 10 5 years to reach the main sequence.

6 度行量輻流輻量力 Protostar hidden by dark, dusty nebula 力量 X 例 4 1 Jets shocks Herbig-Haro objects 量力 Proton-Proton Reaction 1 H + 1 H 2 H + e + + e e + + e MeV 輻 2 H + 1 H 3 He MeV 3 He + 3 He 4 He + 1 H + 1 H MeV 2 X 流 3 H He 度 A 15 M protostar takes about 10 5 years to reach the main sequence... Luminosity (L ( ) 15 M 9 M 5 M Main-sequence 3 M hydrogen fusion 2 M...while a 1 M protostar takes much longer, more than 10 7 years. 1 M 0.5 M temperature (K) Surface 4 yr 10 5 yr 10 6 yr 7 yr 量量量 0.4 ~ 4 M 輻流輻 > 4 M 量流輻 < 0.4 M 輻輻 6

5 L [ergs/s] = emitting power (consumption rate) M

7 藍裂量亮度藍量度了 50 年 50 年年量度 (mass-luminosity relation; ) Roughly L ~ M 3.5 Main-Sequence Lifetime Massive stars are very luminous, L ~ M 3.5 L [ergs/s] = emitting power (consumption rate) M available energy M/L = lifetime of energy generation ~ M 2.5 量 2.5 量例量 10 (10 M ) 100 年 0.3% 數年 Q 藍年什藍年 7

8 量量 0.08 M 度不量 150 M 不烈力輻力不量 0.08~150 M 量 (0.08~0.4 M 輻度度 0.08~0.4 量 (red dwarfs) 度力流 (convection) 狀率年年冷量力度 10 8 K 4 He + 4 He + 4 He 12 C + (triple alpha process) 度狀度降 12 C + 4 He 16 O + 冷 (red giant) 不例 (Cepheid variables) 50 年 100 度 2000 行年 10 8 度行行 8

9 量流 (mass loss) 流量 ~10 14 M 流度 ~10 7 M 什流度 10 km/s 利勒量 2~4 量行 2~4 量度 (degenerate) 狀力度力度不不理列力 (electron degeneracy pressure) 力 1 度不了行 (helium flash) Helium flash 度 3.5 x 10 8 K 度冷度降度力零 (zero age main sequence) 41 度度度 (40%) 6% 度 (5500 K to 5800 K) MS 年不量來來不了冷行狀 (planetary nebulae) 露狀行狀狀行 9

10 (open cluster) 量羅狀 (globular cluster) 量輪量量陸離年離 (turnoff point) 量更年 This star cluster is so young that most of its cool, low-mass stars have not yet arrived at the main sequence. This star cluster is old enough that all of its cool, low-mass stars have arrived at the main sequence: Hydrogen fusion has begun in their cores. Luminosity (L ( ) Main sequence Luminosity (L ( ) Main sequence Surface temperature (K) An H-R diagram of the stars in NGC 2264 Surface temperature (K) An H-R diagram of the stars in the Pleiades (stellar Population) 量 (metal rich) 來 Population I stars 狀金量 (metal poor) Population II stars Hipparcos 料不羅 10

Horizontal Branch Stars core helium fusion and shell hydrogen

Globular cluster M10, d=16,000 ly, size~70 ly across, with ~ 1

Period-luminosty relation Cephei W Virginis Cepheids 度度 (hosting

http://en.wikipedia.org/wiki/image:rochepotential.

11 Horizontal Branch Stars core helium fusion and shell hydrogen fusion (Variable Stars) 不不量 Cepheid variables Cepheids P > 1 d Globular cluster M10, d=16,000 ly, size~70 ly across, with ~ 1 million stars 不量 RR Lyrae variablesrr < 1 d 度 Cepheids Period-luminosty relation Cephei W Virginis Cepheids 度度 (hosting galaxy) 離量離 Q 利 Cepheid variables 量離 A 度離兩了亮度力力 Roche 洛 Restricted 3-body problem. i.e., m << M 1, M 2 In a co-rotating frame, Lagrangian points cf Trojan asteroids For a mathematical derivation, see 11

12 (close binary) (mass transfer) In addition to the WMAP, other L2 point missions include Herschel, Gaia, JWST, etc. Algol (Beta Persei) [ 陵 ] 亮 2.87 亮 B G G B 亮度亮度 B G 年量流度類 Algol Beta Lyrae 離離 (accretion disk) 了離 W Ursae Majoris 度離兩 (mass exchange) 12

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untitled The Nature of the Stars Orion from +7.0 to 2.0 mag sky 量離量亮度度兩亮度度度量 http://www.darksky.org/infoshts/is120.html 亮度 (brightness) 來亮度度離 (apparent magnitude) 來亮度亮數例 1 2 亮 19 30 亮 1 6 亮 100-26.8