Dark Matter

Published on May 27, 2016

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Don’t get puzzled with antiparticles, dark fluid, dark energy or dark flow. Dark matter is the matter which is hypothetically connected to matter which is not visible through a telescope, but, takes into consideration the majority of the matter existing within the universe. The continued existence and composition of the Dark matter is deduced from the gravitational effects that it weighs upon visible matter, radiation, , and on the whole of the universal configuration. There is no direct discovery of the Dark matter, rendering it as one among the unquantifiable elements of contemporary astrophysics.

Mass Energy

Dark matter does not absorb or release light or any sort of electromagnetic radiation, whatever its level. As per the Plank Mission, and on the basis of the standard mode of cosmology, the sum of the mass-energy contained in the Universe, consists of baryonic matter 4.9%, Dark matter 26.8% and the remaining 68.3% consists of dark energy. Consequently, the estimate of dark matter comprises about 84.5% of the sum of the matter contained in the universe, whereas the composition of dark matter and dark energy is 95.1% of the whole mass-energy contained in the universe.

Mass of Dark Matter

According to the hypothesis put forward by Astrophysicists, the survival of the Dark matter is the result of the inconsistency that exists amid the mass of the huge astronomical objects established from the effects of their gravitational force, and of the mass of the visible matter (gas, stars and dust) which they observe. According to the survey conducted, the special effects of gravitation, propose that mass of the astronomical matter is comparatively very much more  huge than the visible matter.

Conjecture of Origin of Dark Matter

  • In the year 1932, Jan Oort, hypothesized Dark matter, although on the basis of inadequate proof, as accountable for the orbital velocities of the stars in the Milky Way. In the year 1933, Fritz Zwicky was the premier person who employed the virial theorem to deduce the existence of unobserved matter; this he assigned to as dunkle Materie which means ‘Dark matter’
  • In 1939, Horace W. Babcock, put forward enough clear proof obtained from the curves of the galaxy rotation, however, it was not related to dark matter.
  • In the 1960s – 1970s, Kent Ford and Vera Rubin were the first persons whose hypothesis postulated “Dark matter’ on the basis of sufficient proof, with the use of galaxy rotation curves.
  • Consequently, several different systematic watching’s pointed out that Dark matter exists in the universe. This included observing through gravitational lenses the surrounding objects through galaxy clusters, like the temperature distribution of the hot gases present in the galaxy, Bullet Cluster, and clusters of galaxies and much more of the recent observations, like the pattern of the anisotropies, observed in the cosmic microwave surrounding. The cosmologists concluded that, the composition of dark matter mainly consists of subatomic particles that are awaiting description. The present study of particle physics focuses on the search of particles, adopting several techniques.

Inferences

Theories on Dark Matter

The extensively recognized clarification related to these phenomena is that there exists Dark matter, which by all means is a composition of the weakly interacting massive particles (WIMPs), whose interaction takes place exclusively by the weak forces and gravity?

There are many other elucidations on this matter; however enough valid proof is not available to prove its correctness. Several experiments to find out dark matter particles via means other than gravitation are in progress

A different theory proposed that a “Hidden Valley” does exist, composed of dark matter of little resemblance to the matter known to us, and they can, through gravity alone interact with the universe.

The Role of Dark Matter in the Universe

Dark matter is the pivot around which rotates the state-of the-art modeling of the cosmic configuration, the development and quantifiable effects on the anisotropies found in the cosmic microwave background (CMB) and formation of the galaxy,. Taking into consideration the above evidences, it is advocated that, considering the clusters of galaxies, galaxies and the universe as a single unit, there is a greater amount of matter than which is observed easily with electromagnetic radiation.

Dark Matter-Baryonic and No baryonic

The Three Theories

Three distinct lines of evidence exist which propose that most of the dark matter is not composed of baryons (normal matter inclusive of neutrons and protons)

Baryonic Matters

  • The Big Bang theory of nuclear synthesis, forecast that 4 to 5 % of the significant density of the universe is composed of baryonic matter, though facts obtained from major configuration and several findings point out that 30 % of the critical density is composed of the whole density of the matter.
  • Gravitational microlensing searches in astronomy indicate that dark compact objects in the Milky Way can be hiding only a small portion of the dark matter in it.
  • A third hypothesis states that 31.7% of the mass-energy available in the universe consists of matter, of which 84.5% is Dark matter.

Thus we arrive at the conclusion that the enormous mass of dark matter present in the universe are not of baryons, hence atoms are not formed by them. Besides, they are incapable of interacting particularly with ordinary matter through electromagnetic forces; there is no electric charge present in dark matter.

Non-Baryonic Matter

Dark matter, which is not baryonic matter, belongs to the imaginary particles, like Axions, if not like the super-symmetrical particles. It is possible for the Neutrinos only to form a tiny portion of the dark matter; this is because of the limitations of the high-red shift galaxies and the large-scale configuration.

Quite different from the baryonic dark matter, non-baryonic dark matter are not components of the elements of the beginning of the universe. Thus its formation is exposed only through its gravitational forces.

The classification of non-baryonic matter falls under the collection of the particle(s) supposed to responsible for its formation, and/or the particular velocity with which it is scattered. (This is because the particles that are heavier have slow motion)

The three familiar hypotheses based on non-baryonic matter are:

Cold Dark Matter (CDM)

With regard to the hypothesis on the cold Dark matter, the matching particles are normally believed as weakly interacting massive particles (WIMP). Cold dark matter accounts for the “bottom-up” configuration of the universe.

Warm Dark Matter (WDM)

Warm dark matter (WDM) is an imaginary outward appearance of dark matter, its characteristics lies between that of the cold dark and the hot dark matter. The well known WDM contestants are Gravitinos and sterile Neutrinos. The WIMPs (weakly interacting massive particles), that are formed in the absence of heat are possibly aspirants for the warm Dark matter

Hot Dark Matter (HDM)

There are possibilities for the hot dark matter as a component of the (massive) neutrinos, however, findings entail that just a small portion of Dark matter is hot matter. Hot dark matter comprises the formation of the “top-down” region of the universe. It is likely that they combine to a certain extent.

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