VIRGOHI21 is a dark halation of Matière located in the Virgo Cluster. This object with the size of a Galaxy, but does not contain any visible star. It was detected with the Radiotéléscope in the band of frequencies known as H-I of the neutral Hydrogène (21 cm wavelength). This discovery would be one of the first confirmations of the theory of the dark matter, which postulates inter alia this matter is acumulerait in galaxies, and even in galaxy cluster, like the matter ordinary, known as “luminous”.

This halation has a mass of about 100 million solar masses, and is located at 50 million light-years of us. The hydrogen detected in VIRGOHI21 does not account for more than one thousandths of the total mass of the halation, which was deduced by its number of revolutions.

Other not very lunimeuses galaxies comprise hydrogen, with probably little dark matter and little or not of stars. Consequently, they are very “light” and are, neither more nor less, that large diffuse hydrogen clouds. The dark matter halations, like VIRGOHI21, have masses much larger, while comprising very little ordinary matter (the “ordinary” matter is made up of Baryon S). It is what explains why this halation does not contain apparently any star.

Other candidates of matter halations sinks were detected before, but VIRGOHI21 is the first which does not contain any star. It is also that which contains, and by far, the most percentage of dark matter.

The debate remains open as for the dark quantity of matter which the universe would contain. Some estimated claim that there could be more galaxies of matter sinks than of ordinary galaxies.

The Matière sinks composes the majority of the mass of the universe, and is present too in the “normal” galaxies. It is the number of revolutions of the visible galaxies, much higher than envisaged, which led to the development of the theory of the dark matter.

The majority of the cosmologists think now that the galaxies were initially made of dark matter after the big bang. The mass of the dark galaxies thereafter attracted hydrogen to form the visible galaxies.

The dark matter halations as VIRGOHI21 are different from the Milky Way, our galaxy, because they did not succeed in attracting hydrogen enough so that are born in their center from stars.