peter laursen
DESCRIPTION
Kosmologi. Peter Laursen. www.dark-cosmology.dk /~pela Dark Cosmology Centre | Niels Bohr Institutet | Københavns Universitet. Astronomi. Kosmologi - hvad?. Kosmologi - hvorfor?. Aristoteles (384 - 322 f.Kr.). Første gennemtænkte model for Universet Den nedre sfære: - PowerPoint PPT PresentationTRANSCRIPT
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www.dark-cosmology.dk/~pela Dark Cosmology Centre | Niels Bohr Institutet | Københavns Universitet
Peter Laursen
Kosmologi
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Astronomi
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Kosmologi - hvad?
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Kosmologi - hvorfor?
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Aristoteles (384 - 322 f.Kr.)
Første gennemtænkte model for Universet
Den nedre sfære:Jord, luft, ild og vand
Den øvre, stjernernes sfære:Æteren
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Aristoteles (384 - 322 f.Kr.)
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Situationen i starten af 1600-tallet:
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Kepler
€
F =Gm1m2
r2,
Newton
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Endeligt eller uendeligt Univers
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Det næste virkeligt store gennembrud:Einsteins
relativitetsteori
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QuickTime™ and a decompressor
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Einsteins relativitetsteori
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QuickTime™ and a decompressor
are needed to see this picture.
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Edwin Hubble (1889 - 1953)
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Nu
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Før
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Endnu før
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Vores Univers må altså have haft en begyndelse.
Kommer det så også til en afslutning engang i fremtiden?
Dette afhænger stoftætheden i Universet:
€
Ω=ρ
ρkritisk
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Et tomt univers udvider sig lineært med tiden: R ∝ t
Masse vil pga. tyngdekraften bremse udvidelsen
Hvis ΩM > 1, kollapser Universet i et "Big Crunch”
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Det totale bidrag til Ω fra almindeligt stof:Stjerner: Ω ~ 0.005
€
Ωnormalstof = 0.046 ± 0.0015
Interstellart gas:Ω ~ 0.005
Gas i galaksehobe:Ω ~ 0.03
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Den umiddelbare konklusion ser ud til at være, at Universet udvider sig for evigt, omend langsommere og langsommere.
Er det nu også rigtigt?
Hvad nu, hvis der er stof, vi ikke kan se?
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Stjernens bane
En galakses masse kan findes ud fra stjernernes baner:
Tyngdekraft
Hastighed
Centrifugalkraft
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En typisk galakse indeholder omkring 5-6 gange så meget masse som det synlige. Denne ekstra masse kaldes "mørkt stof".
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Faktisk blev det mørke stof første gang observeret i 1933 af Fritz Zwicky i Comahoben, der har en masse, der er mindst ti gange så stor som massen af gassen og stjernerne i den.
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Evidens for mørkt stof kommer også fra gravitationel linsning
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Bullet Cluster: Optisk lys
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Bullet Cluster: Optisk + grav. linsn.
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Bullet Cluster: Optisk + X-ray
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Bullet Cluster: Optisk + grav.linsn. + X-ray
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Fra galaktiske rotationskurver og mørkt stof i galaksehobe fås, at
Ω = 0.28 ± 0.01
85% af massen er mørk, men stadig et åbent, ekspanderende Univers.
Hvad med den kosmologiske konstant?
€
Ω=ΩM + ΩΛ
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Den kosmologiske konstant virker som en anti-tyngdekraft, som får Universets udvidelse til at accelerere.
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QuickTime™ and a decompressor
are needed to see this picture.
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Det tidlige Univers: Meget varmt og tæt.Ikke gennemsigtigt for lys.
Det nuværende Univers:Meget koldt og tomt.Gennemsigtigt for lys.
Universets alder: ca. 380.000 år
Den kosmiske mikrobølgebaggrundstråling
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Første gang målt i 1965 af Penzias and Wilson (Nobelpris 1978)Næsten isotrop stråling med <T> = 2.728 K
Den kosmiske mikrobølgebaggrundstråling
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1992: Første måling af ujævnheder - eller anisotropi - i strålingen af den amerikanske satellit COBE
€
δTT
≈ 2 ×10−5 (δT ≈18μK)
Den kosmiske mikrobølgebaggrundstråling
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De små ujævnheder i baggrundsstrålingen er siden vokset og blevet til galakser, stjerner, og i sidste ende os...
Ved at måle ujævnhederne kan man bestemme Universets geometri.
Den kosmiske mikrobølgebaggrundstråling
2001 - nu: WMAP-satellitten måler anisptropien til ekstrem nøjagtighed
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Åbent univers: Ω<1
Fladt univers: Ω < 1
Lukket univers: Ω > 1
Den kosmiske mikrobølgebaggrundstråling
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Bedste bud:
Ωb = 0.05ΩDM = 0.23Ω = 0.72
Universet er fladt,vil udvide sig for evigt,og er domineret af mørkt stof og mørk energi.
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Lyman
ELy = 10.2 eV
0 = 1216 Å
0 = 2.466 X1015 s-1
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ELy = 0.0000000000000000000004 kcal
0 = 0.00001216 cm
0 = 2.466 million GHz
Lyman
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Kvasarer
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DLA linie
Lyman skoven
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Hvordan dannes LyKølestråling (~10%)
Stjernekilder (~90%)
Metagalaktisk felt (~1%)
Unge galakser burde være synlige (Partridge & Peebles, 1967)
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Kosmologisk simulering- The Movie
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Film fjernet
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Diffusion i rum og frekvens
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Monte Carlo kode
L, T, nHI,vbulk
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Udsend foton
^Bestem n
Bestem uatom
Bestem
Slip fri!
Numeriske modeller
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“It would seem that large digital
computers could be applied
very
profitably to this problem”
Osterbrock (1962)
Numeriske modeller
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Surface brightness maps
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Spektrer
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Støv
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Støv = liv
QuickTime™ and a decompressor
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Grunden til at jeg planlægger at vie et arbejdsliv til det her:
+ man kan leve af det...