Fundamental Astronomy

More documents

Recommendations

Info

$P 0.1 Stabilişti natura şsi suma seriilor: a) Σ 1 n\ ; b) Σ arctan 1 n# + n ...$

een made at these wavelengths with the Chandra X-ray satellite and with the Spitzer Space Telescope. The indications from these searches are that at least 3/4 of all supermassive black holes are heavily obscured. Gravitational Lenses. An interesting phenomenon first discovered in connection with quasars are gravitational lenses. Since light rays are bent by gravitational fields, a mass (e. g. a galaxy) placed between a distant quasar and the observer will distort the image of the quasar. The first example of this effect was discovered in 1979, when it was found that two quasars, 5.7 ′′ apart in the sky, had essentially identical spectra. It was concluded that the “pair” was really a double image of a single quasar. Since then several other gravitationally lensed quasars have been discovered (Fig. 18.17). Gravitational lenses have also been discovered in clusters of galaxies. Here the gravitational field of the cluster distorts the images of distant galaxies into arcs around the cluster centre. In addition in 1993 microlensing was observed in the Milky Way, where the brightness of a star is momentarily increased by the lensing effect from a mass passing in front of the star. Thus the study of gravitational lens effects offers a new promising method of obtaining information on the distribution of mass in the Universe. 18.8 The Origin and Evolution of Galaxies Because the speed of light is finite we see distant galaxies at earlier stages in their life. In the next chapter we show how the age of a galaxy with given redshift can be calculated based on the rate of expansion of the Universe. However, this relationship will depend on the cosmological model, which therefore always has to be specified when studying the evolution of galaxies. The beginning of galaxy evolution was marked by the formation of the first stars at a redshift around 10–20. The ultraviolet radiation of the earliest objets reionised the intergalactic gas, which made the Universe transparent to radiation, and thus made the distant galaxies and quasars visible in principle. The largest observed redshifts known at present are about 6.5. According to the currently widely accepted cosmological models most of the matter in the Universe is 18.8 The Origin and Evolution of Galaxies in a form that emits no radiation, and is only observable from its gravitational effects. In this Cold Dark Matter (CDM) theory (see Sect. 19.7) the first systems to collapse and start forming stars were small, with masses like those of dwarf galaxies. Larger galaxies were formed later as these smaller fragments collected into larger clumps. This model, where most stars are formed in small galaxies is usually described as the hierarchical model. Before the introduction of the CDM model, the dominant model was one where the most massive systems are the first to start forming stars, which is often called the monolithic model. We have already seen in Sect. 17.5 that the formation of the Milky Way shows aspects of both types of models. A large part of our theoretical ideas on galaxy evolution is based on numerical simulations of the collapse of gas clouds and star formation in them. Using some prescription for star formation one can try to compute the evolution of the spectral energy distribution and the chemical abundances in the resulting galaxies. The results of the models can be compared with the observational data presented in the previous sections of this chapter. The density distribution of dark matter is expected to be very irregular, containing numerous small-scale clumps. The collapse will therefore be highly inhomogeneous, both in the hierarchical and in the monolithic picture, and subsequent mergers between smaller systems should be common. There are additional complicating factors. Gas may be expelled from the galaxy, or there may be an influx of fresh gas. Interactions with the surroundings may radically alter the course of evolution – in dense systems they may lead to the complete merging of the individual galaxies into one giant elliptical. Much remains to be learned about how the formation of stars is affected by the general dynamical state of the galaxy and of how an active nucleus may influence the formation process. Our observational knowledge of galaxy evolution is advancing very rapidly. Essentially all the relationships described earlier in this chapter have been studied as functions of time. Still, a complete generally accepted description of the way the Universe reached its present state has not yet been established. Here we can only mention a few of the most central aspects of the processes leading to the galaxies we observe to-day. 389
390 18. Galaxies Fig. 18.18. Galaxy counts in the U, B, I, and K wavelength bands. The counts are compared to those in a cosmological model without evolution. The cosmological parameters correspond to the currently preferred “concordance” model (see Sect. 19.5). (H.C. Ferguson et al. 2000, ARAA 38, 667, Fig. 4) Density and Luminosity Evolution The the most basic way of studying the formation and evolution of galaxies is by counting their numbers, either the number brighter than some given magnitude limit (as was already done by Hubble in the 1930’s, see Sect. 19.1) or else the number density as a function of redshift. The counts can be compared with the numbers expected if there is no evolution, which depend on the cosmological model. They can therefore be used either as a cosmological test, or as a test of evolutionary models. However, the present situation is that more reliable cosmological tests are available, and the number counts are mainly used to study the evolution of galaxies. There are two ways in which the number counts are affected by galaxy evolution. In density evolution the actual number of galaxies is changing, whereas in luminosity evolution only the luminosity of individual galaxies is evolving. The simplest form of luminosity evolution is called passive luminosity evolution, and is due to the changing luminosity of stars during normal stellar evolution. Pure luminosity evolution is expected to be predominant in the monolithic picture. In the hierarchical picture density evolution will be more prominent, since in this picture smaller galaxies are to a greater extent being destroyed to produce larger more luminous ones. Figure 18.18 gives an example of the results of number counts. A model without evolution cannot explain these observed counts, and various models incorporating evolutionary effects have to be introduced. However, a unique model cannot be determined using just the number counts. Distant Galaxies. A more direct approach to galaxy formation is the direct search for the most distant objects visible. In Fig. 18.19 we show the Hubble Deep Field (HDF), an area of the sky observed at several wavelengths with the Hubble Space Telescope using a very long exposure. These images show large numbers of galaxies with redshifts about 2.5–3.5, when the Universe was about 2 Ga old. The galaxies visible in the HDF appear to be bluer and more irregular than the Fig. 18.19. The Hubble Deep Field South in the direction of the Tucana constellation (NASA; a colour version of the same picture is seen as Plate 33 in the colout supplement)
Page 2:
Fundamental Astronomy
Page 5 and 6:
Dr. Hannu Karttunen University of T
Page 7 and 8:
VI Preface to the First Edition The
Page 9 and 10:
VIII Contents 5.6 Continuous Spectr
Page 11 and 12:
X Contents 16. Star Clusters and As
Page 14 and 15:
1. Introduction 1.1 TheRoleofAstron
Page 16 and 17:
1.2 Astronomical Objects of Researc
Page 18 and 19:
theory of relativity must be used t
Page 20 and 21:
of the gas may be 10 −21 kg m −
Page 22 and 23:
12 2. Spherical Astronomy angles co
Page 24 and 25:
14 or 2. Spherical Astronomy sin B
Page 26 and 27:
16 2. Spherical Astronomy defined t
Page 28 and 29:
18 2. Spherical Astronomy the verna
Page 30 and 31:
20 2. Spherical Astronomy pole. The
Page 32 and 33:
22 2. Spherical Astronomy Fig. 2.16
Page 34 and 35:
Page 36 and 37:
26 2. Spherical Astronomy
Page 38 and 39:
Page 40 and 41:
30 2. Spherical Astronomy numbers,
Page 42 and 43:
32 2. Spherical Astronomy In the 19
Page 44 and 45:
34 2. Spherical Astronomy mid-Septe
Page 46 and 47:
36 2. Spherical Astronomy correspon
Page 48 and 49:
38 2. Spherical Astronomy second of
Page 50 and 51:
2. Spherical Astronomy 40 Since ∆
Page 52 and 53:
42 2. Spherical Astronomy For the s
Page 54 and 55:
44 2. Spherical Astronomy red. What
Page 56 and 57:
3. Observations and Instruments Up
Page 58 and 59:
the long, oblique path through the
Page 60 and 61:
Fig. 3.6a-e. Diffraction and resolv
Page 62 and 63:
3.2 Optical Telescopes Fig. 3.10. T
Page 64 and 65:
3.2 Optical Telescopes Fig. 3.13. T
Page 66 and 67:
so thin that it absorbs very little
Page 68 and 69:
3.2 Optical Telescopes 59
Page 70 and 71:
3.2 Optical Telescopes 61
Page 72 and 73:
3.2 Optical Telescopes ◭ Fig. 3.1
Page 74 and 75:
and CCD-cameras have largely replac
Page 76 and 77:
Fig. 3.22a-e. The principle of read
Page 78 and 79:
than a prism. The dispersion can be
Page 80 and 81:
3.4 Radio Telescopes Fig. 3.25. The
Page 82 and 83:
Fig. 3.27. The Atacama Large Millim
Page 84 and 85:
Fig. 3.30. The VLA at Socorro, New
Page 86 and 87:
Fig. 3.31. (a) X-rays are not refle
Page 88 and 89:
Fig. 3.33. Refractors are not suita
Page 90 and 91:
tored by laser interferometers. If
Page 92 and 93:
4. Photometric Concepts and Magnitu
Page 94 and 95:
If we are outside the source, where
Page 96 and 97:
magnitudes can be equal, the flux d
Page 98 and 99:
flux L will now decrease with incre
Page 100 and 101:
this line is extrapolated to X = 0,
Page 102 and 103:
since due to extinction, radiation
Page 104 and 105:
96 5. Radiation Mechanisms Fig. 5.1
Page 106 and 107:
98 5. Radiation Mechanisms From (5.
Page 108 and 109:
100 5. Radiation Mechanisms Fig. 5.
Page 110 and 111:
Page 112 and 113:
104 5. Radiation Mechanisms We now
Page 114 and 115:
5. Radiation Mechanisms 106 Again F
Page 116 and 117:
Page 118 and 119:
110 5. Radiation Mechanisms We can
Page 120 and 121:
112 5. Radiation Mechanisms differe
Page 122 and 123:
114 6. Celestial Mechanics The solu
Page 124 and 125:
116 6. Celestial Mechanics prove (6
Page 126 and 127:
118 6. Celestial Mechanics in the d
Page 128 and 129:
120 6. Celestial Mechanics But cons
Page 130 and 131:
122 6. Celestial Mechanics by the e
Page 132 and 133:
124 6. Celestial Mechanics Substitu
Page 134 and 135:
126 6. Celestial Mechanics a cloud
Page 136 and 137:
128 6. Celestial Mechanics Since th
Page 138 and 139:
130 6. Celestial Mechanics Exercise
Page 140 and 141:
132 7. The Solar System Fig. 7.1. (
Page 142 and 143:
134 7. The Solar System for each ob
Page 144 and 145:
136 7. The Solar System Fig. 7.5. L
Page 146 and 147:
138 7. The Solar System Inserting t
Page 148 and 149:
140 7. The Solar System Therefore o
Page 150 and 151:
142 7. The Solar System Fig. 7.10.
Page 152 and 153:
144 7. The Solar System behaves mor
Page 154 and 155:
146 7. The Solar System Table 7.1.
Page 156 and 157:
Page 158 and 159:
150 7. The Solar System of the plan
Page 160 and 161:
152 7. The Solar System If we denot
Page 162 and 163:
154 7. The Solar System where F⊥
Page 164 and 165:
Page 166 and 167:
158 7. The Solar System larized fea
Page 168 and 169:
Page 170 and 171:
162 7. The Solar System The outer c
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
168 7. The Solar System weak and co
Page 178 and 179:
170 7. The Solar System amount of w
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
176 7. The Solar System ter the rin
Page 186 and 187:
178 7. The Solar System face, most
Page 188 and 189:
180 7. The Solar System The F ring,
Page 190 and 191:
182 7. The Solar System Herschel hi
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
188 7. The Solar System liding, sin
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
196 7. The Solar System of this mat
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
202 7. The Solar System Near the po
Page 212 and 213:
204 7. The Solar System be solved f
Page 214 and 215:
8. Stellar Spectra All our informat
Page 216 and 217:
which appears as irregular fluctuat
Page 218 and 219:
8.2 The Harvard Spectral Classifica
Page 220 and 221:
ate of ionization is essentially de
Page 222 and 223:
lines of titanium, scandium and van
Page 224 and 225:
efore τ = 1, i. e. the radiation i
Page 226 and 227:
yielding Iν(0,θ)= Sν(τ ∗ ) +
Page 228 and 229:
222 9. Binary Stars and Stellar Mas
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
10. Stellar Structure The stars are
Page 236 and 237:
where a = 4σ/c = 7.564 × 10−16
Page 238 and 239:
where me is the electron mass and N
Page 240 and 241:
is produced by the proton-proton (p
Page 242 and 243:
oxygen, which in turn reacts to for
Page 244 and 245:
According to (4.7), (4.4) and (5.16
Page 246 and 247:
Example 10.6 The Radiation Pressure
Page 248 and 249:
11. Stellar Evolution In the preced
Page 250 and 251:
increases. The stellar surface temp
Page 252 and 253:
Since stars are most likely to be f
Page 254 and 255:
Fig. 11.4a-c. Energy transport in t
Page 256 and 257:
Fig. 11.5. The structure of a massi
Page 258 and 259:
tract to planetlike brown dwarfs. S
Page 260 and 261:
Fig. 11.10a-f. Evolution of a low-m
Page 262 and 263:
Fig. 11.12. The Wolf-Rayet star WR
Page 264 and 265:
In a neutron capture, a nucleus wit
Page 266 and 267:
This is several orders of magnitude
Page 268 and 269:
264 12.TheSun Fig. 12.2. (a) The ro
Page 270 and 271:
266 12.TheSun according to the heli
Page 272 and 273:
268 12.TheSun shines into view for
Page 274 and 275:
270 12.TheSun was established that
Page 276 and 277:
272 12.TheSun Fig. 12.11. In pairs
Page 278 and 279:
274 12.TheSun Fig. 12.15. (a) Quies
Page 280 and 281:
276 12.TheSun Fig. 12.17. An X-ray
Page 282 and 283:
13. Variable Stars Stars with chang
Page 284 and 285:
Fig. 13.3. The variation of brightn
Page 286 and 287:
Fig. 13.5. The lightcurve of a long
Page 288 and 289:
duced when the carbon condenses int
Page 290 and 291:
13.3 Eruptive Variables Fig. 13.12.
Page 292 and 293:
Fig. 13.15. Supernova 1987A in the
Page 294 and 295:
14. Compact Stars In astrophysics t
Page 296 and 297:
about 1.4 M⊙, which is thus the u
Page 298 and 299:
1968. In the following year it was
Page 300 and 301:
ditions required for hypernova expl
Page 302 and 303:
This is greater than the speed of l
Page 304 and 305:
Fig. 14.12. Scale drawings of 16 bl
Page 306 and 307:
are (or, in the radio case, have on
Page 308 and 309:
14.6 Exercises Exercise 14.1 The ma
Page 310 and 311:
308 15. The Interstellar Medium Fig
Page 312 and 313:
310 15. The Interstellar Medium R d
Page 314 and 315:
312 15. The Interstellar Medium pol
Page 316 and 317:
Page 318 and 319:
Page 320 and 321:
318 15. The Interstellar Medium Tab
Page 322 and 323:
Page 324 and 325:
322 15. The Interstellar Medium met
Page 326 and 327:
324 15. The Interstellar Medium
Page 328 and 329:
326 15. The Interstellar Medium He
Page 330 and 331:
Page 332 and 333:
330 15. The Interstellar Medium up
Page 334 and 335:
332 15. The Interstellar Medium hav
Page 336 and 337:
334 15. The Interstellar Medium len
Page 338 and 339:
336 15. The Interstellar Medium dro
Page 340 and 341: 338 15. The Interstellar Medium the
Page 342 and 343: 340 16. Star Clusters and Associati
Page 348 and 349: 17. The Milky Way On clear, moonles
Page 350 and 351: Fig. 17.3. The directions to the ga
Page 352 and 353: classes of stars are main sequence
Page 354 and 355: Fig. 17.9. The size of the volume e
Page 356 and 357: lar material similarly moves in the
Page 358 and 359: Fig. 17.14. In order to derive Oort
Page 360 and 361: Fig. 17.17. The radial velocity as
Page 362 and 363: a suitable mass distribution, such
Page 364 and 365: esting because it may be a small-sc
Page 366 and 367: material constituting the galaxy. I
Page 368 and 369: 18. Galaxies The galaxies are the f
Page 370 and 371: Fig. 18.3. The classification of no
Page 372 and 373: 18.1 The Classification of Galaxies
Page 374 and 375: Fig. 18.7. Compound luminosity func
Page 376 and 377: In order to measure the mass at eve
Page 378 and 379: length r0 = 1-5 kpc. In Sc galaxies
Page 380 and 381: 18.4 Dynamics of Galaxies We have s
Page 382 and 383: gas. Some normal spirals may have b
Page 384 and 385: the Large and Small Magellanic Clou
Page 386 and 387: stars are forming and evolving into
Page 388 and 389: panion galaxy. The tail is interpre
Page 392 and 393: galaxies in our present neighbourho
Page 394 and 395: 394 19. Cosmology tographs form an
Page 396 and 397: 396 19. Cosmology Fig. 19.3. Hubble
Page 398 and 399: 398 19. Cosmology element after hyd
Page 400 and 401: 400 19. Cosmology 19.3 Homogeneous
Page 402 and 403: 402 19. Cosmology The potential ene
Page 404 and 405: 404 19. Cosmology In an expanding c
Page 406 and 407: 406 19. Cosmology about 40,000 degr
Page 408 and 409: 408 19. Cosmology rather slowly. In
Page 410 and 411: 410 19. Cosmology Fig. 19.15. Corre
Page 412 and 413: 412 19. Cosmology where Ω0 = ρ0/
Page 414 and 415: 414 19. Cosmology Example 19.2 Find
Page 416 and 417: 416 20. Astrobiology According to t
Page 418 and 419: 418 20. Astrobiology of spiral gala
Page 420 and 421: 420 20. Astrobiology Fig. 20.2. Bla
Page 422 and 423: 422 20. Astrobiology reached 10% of
Page 424 and 425: 424 20. Astrobiology Now panspermia
Page 426 and 427: 426 20. Astrobiology 20.9 Detecting
Page 428 and 429: 428 20. Astrobiology cles that we s
Page 430 and 431: Appendices 431
Page 432 and 433: Ellipse. Equation in rectangular co
Page 434 and 435: A and B can be determined graphical
Page 436 and 437: When using matrix formalism it is c
Page 438 and 439: Similarly, a volume integral I = f
Page 440 and 441:
B. Theory of Relativity Albert Eins
Page 442 and 443:
time interval between the events is
Page 444 and 445:
C. Tables Table C.1. SI basic units
Page 446 and 447:
Table C.6. The Sun Property Symbol
Page 448 and 449:
Table C.11. Osculating elements of
Page 450 and 451:
Discoverer Year of a Psid e i r M
Page 452 and 453:
Table C.16. Periodic comets with se
Page 454 and 455:
Table C.17 (continued) C. Tables Na
Page 456 and 457:
C. Tables Table C.19. Some double s
Page 458 and 459:
Table C.22. Optically brightest gal
Page 460 and 461:
Table C.23 (continued) Abbreviation
Page 462 and 463:
C. Tables Table C.26. Millimetre an
Page 464 and 465:
Table C.27 (continued) Satellite La
Page 466 and 467:
468 Answers to Exercises 6.2 a = 1.
Page 468 and 469:
470 Answers to Exercises Chapter 17
Page 470 and 471:
472 Further Reading Morrison (ed.):
Page 472 and 473:
474 Further Reading Maps and Catalo
Page 474 and 475:
Name and Subject Index A aberration
Page 476 and 477:
coherent radiation 95 Cold Dark Mat
Page 478 and 479:
forbidden transition 101, 332 four-
Page 480 and 481:
Kellman, Edith 212 Kepler’s equat
Page 482 and 483:
nautical mile 15 nautical triangle
Page 484 and 485:
Reber, Grote 69 recombination 95, 9
Page 486 and 487:
synchronous rotation 135 synchrotro
Page 488 and 489:
Colour Supplement 491
Page 490 and 491:
Plate 14. The first view from the s
Page 492 and 493:
Plate 1 Plate 2 Colour Supplement 4
Page 494 and 495:
Plate 6 Plate 5 Colour Supplement 4
Page 496 and 497:
Plate 9 Colour Supplement Plate 10
Page 498 and 499:
Page 500 and 501:
Page 502 and 503:
Plate 23 Plate 24 Colour Supplement
Page 504 and 505:
Colour Supplement Plate 29 507
Page 506 and 507:
show all

Fundamental Astronomy

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?