Dark matter, definition and study. A-Z index of Cognitio.

In Cosmology with dark matter, it is defined as a hypothetical component of matter that is not directly observable, since, unlike the known material, does not emit electromagnetic radiation and is manifested solely through gravitational effects.

 Based on various experimental observations it is assumed that dark matter constitutes the vast majority, almost 90%, of the mass present in the universe. In 1933, astronomer Fritz Zwicky was studying the motion of masses of galaxies far and wide, in particular, the cluster of Chioma and that of the Virgin.

Zwicky estimated the mass of each storage galaxy based on its luminosity and added all the galactic masses to get the total mass of the stock. He then obtained a second independent estimation of the total mass, based on the measurement of the dispersion of individual galaxy velocities in the stock; This second dynamic mass estimate was 400 times larger than galaxy-based estimation. Although experimental evidence was already in Zwicky’s time, it was only in the seventies that scientists began to explore this discrepancy systematically and that the existence of dark matter began to be considered. Considering the stars at the periphery of a spiral galaxy with orbital velocities normally observed at 200 kilometers per second, if the galaxy was composed only of the visible matter these stars would abandon it in a short time, as their orbital velocities are four times more big of the escape speed from the galaxy. Given that no galaxies are being dispersed in this way, there must be mass within them that is not taken into account when summing up the mass of all visible parts. Another possible proof of the existence of dark matter is given by the gravitational lenses. The visible mass is insufficient to create a gravitational lens, whereby massive amounts of dark matter are precipitated, resulting in a total mass capable of diverting the path of light. 

In 2008, thanks to the study of several researchers, including French and Canadian coordinated by the Institute of Astrophysics in Paris, there was another important indication of the presence of dark matter. Using the Canadian-France-Hawaii Telescope (Cfht) telescope, located on Mauna Kea Mountain in Hawaii, the scholars observed thousands of images to verify the deviation that light traveled in its cosmic journey, noting that it was diverted to places where it did not masses were visible. Observations of these gravitational effects are one of the greatest evidence of the existence of dark matter. On April 3, 2013, NASA scientists reported that a trace of dark matter could have been detected by the Alpha Magnetic Spectrometer on the International Space Station.

The first results of the “Space-borne Alpha Magnetic Spectrometer” show an excess of high energy positron in cosmic rays, for which one of the possible explanations is the presence of dark matter.

Dark matter, definition and study. A-Z index of Cognitio.



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Dark matter, definition and study. A-Z index of Cognitio.

Dark matter