揭開宇宙的面紗 -宇宙中的物質和非物質

『從原子到宇宙』課程第十五週

胡維平

國立中正大學化學暨生物化學系

01/02/2014

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hydrogen 10,000,000 sulfur 95

helium 1,400,000 iron 80

oxygen 6,800 argon 42

carbon 3,000 aluminum 19

neon 2,800 sodium 17

nitrogen 910 calcium 17

magnesium 290all other elements

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silicon 250 . .

Number of atoms per 10,000,000 of hydrogen

目前宇宙中各種原子之含量

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What particles are really elementary (indivisible)?

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Proton (+) Neutron (0)

Inner Structure of Nucleons

Particles of Matter and Messenger

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Particle and Forces in Standard Model

String Theory in 11-D?

Antimatter

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Predicted by DiracRelativity + Quantum Mechanics

pair production

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Charge-Parity (CP) Symmetry

Parity violation proposed by Tsung-Dao Lee and Chen Ning Yang in 1956, and experimentally observed by Chien-Shiung Wu. Her cobalt 60 experiment proved that Lee and Yang hypothesis on parity violation by weak interaction was right. Pauli had to admit that "God is a little left-handed".

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decays into two charged pions (with CP=+1); the other is Klong with longer half-life, a CP state of -1 and decay into three neutral pions (with CP=-1). The 1964 experiment by Cronin and Fitch looked for the decay products of Klong. They observed a few decays of the Klong turning into pairs of oppositely charged pions: about 1 out of a total of 500 decays. This kind of decay arrives at a final CP state that is different from the initial CP state and proves that CP symmetry was not preserved exactly by the weak interaction.

CP ViolationThe neutral K meson Ko (a particle that contains a strange quark and a strange quark) manifests itself in two modes with respect to the weak interaction. One mode is labelled Kshort with shorter half-life, a CP state of +1 and

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Discovery of Dark Matter

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Dark-Matter Halo of Our Galaxy

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The observed positions of 135 gravitationally lensed images of 42 background galaxies was used to calculate the location and amount of dark matter in the massive galaxy cluster Abell 1689, which contains around 1,000 galaxies around 2.2 billion light-years away.

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Composition of Our Universe

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The data from Planck imply that the age of the Universe is 13.82 billion years. (2013/3)

Recent Results from the Planck Spacescraft

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WMAP data reveals that its contents include 4.6% atoms, the building blocks of stars and planets. Dark matter comprises 23% of the universe. This matter, different from atoms, does not emit or absorb light. It has only been detected indirectly by its gravity. 72% of the universe, is composed of "dark energy", that acts as a sort of an anti-gravity. This energy, distinct from dark matter, is responsible for the present-day acceleration of the universal expansion. WMAP data is accurate to two digits, so the total of these numbers is not 100%. This reflects the current limits of WMAP's ability to define Dark Matter and Dark Energy. 20

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Proposed explanations for dark matter

1.Brown dwarf stars and similarly massive but relatively non-luminous objects. Astronomers have in fact invented a new name for a class of objects that include brown dwarf stars and other massive objects: Massive Compact Halo Objects, or MACHOs.2.Supermassive black holes. Astronomers are now attempting to detect these objects by their relativistic effects on light, in which they act as lenses.3.New, previously unknown forms of matter. Many cosmologists have formed hypotheses that suggest entirely new particles of matter. They call these Weakly Interacting Massive Particles, or WIMPs. Other cosmologists have suggested other types of particles, named axions. The recently sought Higgs boson is another proposed dark-matter elementary particle.4.A new theory of gravity. In 1983, Mordecai Milgrom first suggested that Newtonian dynamics was insufficient to explain the gravitational interactions of massive objects like galaxies and galactic clusters. He therefore suggested a Modified Newtonian Dynamic, or MOND, in which gravitational attraction varied inversely to the first power of the orbital radius, not its square as Newton originally assumed.5.Neutrinos, which are detected and fall under the category of "warm dark matter" based on their momentum. However, they only account for a small fraction of the dark matter required to explain the structure of galaxies.

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Massive astrophysical compact halo object, or MACHO, is a general name for any kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a body composed of normal baryonic matter, which emits little or no radiation and drifts through interstellar space unassociated with any solar system. Since MACHOs would not emit any light of their own, they would be very hard to detect. MACHOs may sometimes be black holes or neutron stars as well as brown dwarfs or unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs. Theoretical work simultaneously also showed that ancient MACHOs are not likely to account for the large amounts of dark matter now thought to be present in the universe. The Big Bang as it is currently understood couldn‘t produce enough baryons without causing major problems in the observed elemental abundances.

MACHOS

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Weakly interacting massive particles or WIMPs, are hypothetical particles serving as one possible solution to the dark matter problem. These particles interact through the weak force and gravity, and possibly through other interactions no stronger than the weak force. Because they do not interact with electromagnetism they cannot be seen directly, and because they do not interact with the strong nuclear force they do not react strongly with atomic nuclei.

WIMPS

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The pink region in the image is hot gas, glowing in X-rays detected by the NASA satellite, Chandra. The blue region represents our best estimate of where the matter in the cluster is, as traced by its effect on the light from the background galaxies. Essentially, the 'normal' matter, represented by the x-ray radiation, is at the centre of the object, while the total mass is much more spread out. This is exactly what we would expect if the majority of the mass in the cluster was in the form of Cold Dark Matter.

MONDpositive and negative evidences

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The Solar Neutrino Problems

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The Nobel Prize in Physics 2011

awarded "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae" with one half to Saul Perlmutter and the other half jointly to Brian P. Schmidt and Adam G. Riess.

Saul Perlmutter Brian P. Schmidt Adam G. Riess

Lawrence Berkeley National Laboratory

Australian National University Johns Hopkins University and Space Telescope Science Institute

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Models of Cosmology

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Measuring the Distance and the Standard Candles

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Parallelax

Cepheid Variables

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Type Ia Supernova

Chandrasekhar limit = 1.4 M ⊙(solar mass)

almost always the same brightness

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A new supernova, SN 2011fe, has been reported on Aug 24, 2011, in M101 the famous "Pinwheel" galaxy in Ursa Major. This supernova was caught when it was still rising, giving to the astronomers a chance to track it since the beginning of the explosion. It resulted in a type- Ia SN. M101 was discovered by P. Méchain in 1781 and its distance is estimated in about 20 millions of light years

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The Palomar Transient Factory caught SN 2011fe in the Pinwheel Galaxy in the vicinity of the Big Dipper on August 24, 2011. Found just hours after it exploded and only 21 million light-years away, the discovery triggered the closest-ever look at a young type Ia supernova.

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Our Accelerating Expanding Universe Dark Energy