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10 wonderful-universe


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lezing NIOZ

lezing NIOZ

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  • 1. Galaxies , stars and their origin More universes than ours ? Earth-like planets ? C. de Jager
  • 2.  The constellation Andromeda contains the ‘nebula’ M 31
  • 3.  It took 2.5 million years for these photons to reach our eyes When the Neanderthalers still lived here these photons had already finished 95% of their trip
  • 4.  That ‘nebula’ is our neighbouring sister-galaxy: Messier 31
  • 5.  Distance 2.5 million light years With our galaxy it is one of the two largest of the ‘local group of galaxies’ (which contains some 20 extragalactic systems) Diameter about 150 000 light years About 1012 stars Total mass ~1.3 times that of our galaxy Our sister-galaxy
  • 6.  Many more spiral-galaxies in the sky - the whirlpool galaxy, distance 25 Mlj
  • 7.  M83: a barred spiral – like our galaxy; at 15 Mlj
  • 8.  The sombrero galaxy – gas and dust in the equatorial plane at 30 Mlj
  • 9.  Groups of galaxies: the Virgo cluster at 53 Mlj
  • 10.  Part of the Coma cluster; hundreds of galaxies at 320 Mlj
  • 11.  Deep space up to some 12 Glj (Giga light years) - – more galaxies than stars on this picture
  • 12.  Farthest known galaxy– at 13.1 Glj
  • 13.  That was a rapid view of our Universe There were remarkable developments in the early 20th century
  • 14.   An essential question for Einstein (1915): Why does the universe not collapse – the Earth existsed for hundreds of millions of years if not longer; the galaxies most probably too  Did the universe exist that long without collapsing?  To overcome this Einstein introduced an additional term in his formulae – characterized by the Greek capital Lambda. Keeping the universe in shape Einstein’s dilemma
  • 15.   Ten years after Einstein Hubble found that the Universe is expanding  Around 1920 - 30 that was already predicted by De Sitter, Friedman and Lemaître  Their suggestion: Universe is either expanding or collapsing or (most improbable) just in balance  Hubble could measure distances and found: it is expanding  Einstein: “Introducing Lambda was my biggest error” Einstein’s ‘biggest error’
  • 16.  Hubble’s first diagram – 1929 (note: one parsec = 3.26 light years)
  • 17.   A special type of supernovae (Supernovae type Ia) is the most reliable standard candle  A supernova Ia is due to the explosion of a white dwarf star that, by collecting mass from a companion star, exceeds its limiting mass of 1.4 solar masses  Then it produces a radiation flux of 1010 times solar radiation flux. Therefore visible till far in the depths of the Universe  All SN Ia are equally bright – that makes them a good standard candle Later improvements based on a reliable standard candle
  • 18.
  • 19.   From Hubble diagram we derive: Universe originated 13,8 Gigayears ago; must have been very small at that time – how small?  Lemaître (Leuven) introduced L’atome primitif: the universe started extremely small ; elaborated by Gamov  The hypothesis of an explosion with extremely small origin met with much sceptisism  Hoyle, cynically: “These fantasists with their big bang”  Gradually – after more data and many investigations – the conclusion became inevitable “The day without yesterday”(Lemaître)
  • 20.  It was not an explosion ! Not an explosion of matter – space originated and grew Before, there was no space; nor did time exist. Before? That notion too had no sense
  • 21.   Universe, space and time, originated from an instability of the absolute vacuum – the Big Bang, but how?  Perhaps the Casimir-Polder hypothesis (1948)?  Basis: even the absolute vacuum does contain energy in volumes as small as the Planck length – emergence and decay of very enegetic virtual particles with positive and negative energy explosions, and even with positive and negative time excursions.  Could an accumulation of energy in the sub-Planck domain lead to an explosion followed by expansion and decreasing temperature? Still very open question Big Bang
  • 22.   In times shorter that Planck time (1.35 x !0-43sec) and space smaller than Planck length (4.05 x 10-35 meter) notions time and space lose their meaning. Virtual particle can originate and decay.  Formation involves positive and negative energy of order of Planck energy (2x 109 Joule) and associated pressures  Corresponding temperature is 3.55x 032 K  Could such an explosion have given rise to the Universe?  And: why then only one universe ? A multiverse? The Planck era and the Multiverse
  • 23.   After its formation the universe expanded and cooled  Basic constituents of chemcal elememts originated:  Quark–gluon liquid after ~ 10-6 s; T = 1013 K  Thereafter protons and neutrons formed and then the simplest atomic nuclei (H, He, Li)  After 300 seconds: T has decreased to ~ 109 K, universe consisted of positive ions of Hydrogen, Deuterium, Helium-3, Helium-4, Lithium and many electrons  After 370 000 years: T smaller than 4000 K; recombination of protons and electrons: universe became transparent After Planck era: formation of first chemical elements
  • 24.  This was the standard picture It was accepted till end of last century. Recent new developments
  • 25.   (a) Study of motions in (groups of) galaxies shows there must exist more matter than what is visible  Initial estimates: there is about five to ten times more invisible than visible matter. What is it?  Dark matter – nice name but explains nothing  (b) But additionally it was found that expansion of universe is accelerating (Einstein’s Lambda returns!)  Enormous energy needed for this acceleration  Dark energy – nice name but explains nothing Dark matter and dark energy
  • 26.   The relation between velocity of expansion and distance is not linear – the expansion accelerates!  Acceleration by some form of energy. How much?  We tranform energy into mass with E = m.c2  Best agremeent is found for 30% mass (visible and invisible) and 70% mass corresponding with dark energy  See next graph More about the acceleration
  • 27.
  • 28.  A closer look at the developing universe After the first few minutes, the Universe, while continuing to cool down, still consisted only of atoms of Hydrogen and Helium.
  • 29.   By recombination of electrons and protons the first hydrogen atoms formed. The universe became practically transparent (apart from absorption by He atoms)  This happened after some 370 000 years . At that time T had decreased till below 4000 K – but by exansion of universe we see T = 2.7 K  Do stars and galaxies originate at that time? Can we see that ?  WMAP and Planck satellites, observing at mm wavelengths gave image of the universe at that time  Result was disappointing: practically smooth universe After 370 000 years
  • 30.  Planck satellite observing at many mm wavelengths
  • 31.  The universe, 370 000 years old; very smooth; most fluctuations ~ 0.2 mK
  • 32.  Power spectrum
  • 33.   Total relative mass of visible matter (baryons and electrons) is 0.0486 ± 0.0007  Total relative mass of dark matter is 0.273 ± 0.006  Total relative mass correspoding with dark energy is 0.68 ± 0.02  Expansion velocity increases wit 67.3 ± 1.2 km/sec/megaparsec (Hubble constant); age of univere 13.8 Giga-years  Hence: visible matter: 5%; dark matter: one-fourth; dark energy: two-thirds Results of analysis
  • 34.  Birth of galaxies, stars and planets At that time: only Hydrogen-Helium bodies Heavier atoms did not exist Hence: no rocky planets possible Life was neither possible
  • 35.   With the given densities and radiation flux only fairly small individual clouds of gas can form  Mass of order 10 000 solar masses.  This happened after 300 to 500 million years  Gradually H2 molecules form, a fraction of 0.001 to 0.000 1 produces sufficient cooling allowing for more mass accretion; thus these clouds grew  After about 600 million year the mass has increased to 1 – 10 million solar masses; not yet a galaxy.  We call these objecs: proto-galaxies Proto-galaxies
  • 36.   Small density fluctuations in the proto-galaxies can lead to fragmentation followed by further contraction – thus the first stars form  Size is limited by the absorption in the atmospheres – if this is large enough, atmophere expands and escapes. This limits the size of the star  Present most massive stars contain enough absorbing matter to keep their mass below 60 – 80 solar; their radiation flux is one million times the solar value.  In contrary: the earliest stars of the universe could reach masses up to a thousand solar masses The first stars - gigantic objects
  • 37.   The early H-He stars had high central pressure and temperature. Intense nuclear radiation and hence intense radiation flux ( ~108 to 109 times solar value)  Hence shortlived star  Compare: sun is expected to live for 10 Gigayears; star of 100 solar masses lives only 1 – 3 million years  Star of 1000 solar masses is expected to live not longer than 30.000 years; ; they radiate few 100 million times more intense than the sun  Explosion at end of life – hypernova  Remaining core becomes black hole of ~ 100 solar masses Short living objects; hypernovae
  • 38.   At the end of the life of a star heavier than ~ 10 solar masses it explodes  Core remains and becomes neutron star or black hole  This proces is called a supernova. Atomic nuclei up to Fe, Ni … etc. .. are formed during explosion  The explosion of the initial very large stars of many hundres of solar masses are called hypernovae  During their explosions large numbers of high-mass atomic nuclei are formed and spread over space Compare super- and hypernovae
  • 39.  An ordinary supernova and its galaxy SN1994D
  • 40.  Remnants of a supernova expand with 5000 – 10.000 km/sec
  • 41.  GammaRay Burst 030329; may 2003 (compare brightness of burst with that of neighbour galaxy!) Star was 40 solar; new elements up to Ni formed
  • 42.  Gamma ray burst associated with hypernova 16-09-2008
  • 43.  Source distance : 12.2 Gigalightyears
  • 44.   Universe exists for 13.8 Gigayears  0.37 million years: universe becomes transparent  400 million years: first matter accumulated  600 million years: protogalaxies; first hypergiant stars, hundreds to thousand times larger than sun  800 million years: first present-days galaxies; smaller stars  After 1 to 2 Gigayears: first sunlike stars Summarizing (all data are aproximative)
  • 45.  We exist You and me: We exist thanks to the supergiant stars and to the super- and hypernovae
  • 46.   Sun-like stars can only exist if they contain enough absorbing matter, which is atoms heavier than He  In cores of massive stars (20 – 80 times sun) elements such as O, Ne, Mg, Si are formed  In ‘ordinary’ supernovae (mass above 10 solar, and up to ~ 80 solar) chemical elements up to atomic numbers around Fe and Ni are formed during their explosion  In hypernovae (more massive stars) formation of still much massive chemical elements  Thanks to such stars rocky planets and life can exist We exist thanks to massive stars
  • 47.  Back to earth Earth-like planets could therefore exist in the universe But how about life?
  • 48.  First extrasolar planets discovered in 1992 and 1995. Presently some 1800 known and 3000 candidates; various discovery methods
  • 49.  Limited habitable area
  • 50.  Planets in habitable area star: Gliese 667C
  • 51.   Only big planets can yet be discovered  Only those that revolve close to the parent star  Thus ‘hot Jupiters’ are frequently found  The Earth reflecting only fraction 10 -10 of the sun’s light, occulting some 10-4 part of the sun and revolving around the sun in a time as long as one year, would be very difficult to discover  But Jupiter too would be a difficult object in spite of its big mass, because of its long revolution time Limitations to discoveries
  • 52.  A new approach: starlight being eliminated by interferometry; three planets found
  • 53.   Set of four spacecrafts, pointing same direction  Mutual relative distances and distance to fifth spacecraft to be controlled with extreme precission  Light sent from the four to the central spacecraft  By interferometry light of star is eliminated; light of planet(s) remains  Residual light inspected spectroscopically –search for molecules that relate to life  This is a proposal to ESA – not yet accepted A fascinating proposal: the Darwin mission
  • 54.  Darwin spacecraft cluster
  • 55.  IR spectra of Earth, Venus, Mars: note O2 , H2O , CO2
  • 56. Containing at least one small rocky planet, surrounded by a thin layer of water and much thinner layer of gas. A good Universe to live in
  • 57. Go to page: presentations ; there to Universe See also: oerknal Eerste melkwegstelsels Eerste sterren Hete reuzenplaneten