Is dark matter a gas

 

From theoretical considerations, a value for the total mass of galaxy clusters is obtained which, at around 1.2 quadrillion solar masses, is significantly higher than the value that one would expect from counting and weighting the galaxies according to luminosity.
Fritz Zwicky discovered this discrepancy as early as 1933 and concluded from it that invisible mass must be present in the galaxy cluster (dark matter). He arrived at the unimaginable size of a factor of 30 to 40 more mass.

Another indication of this dark matter can be found in the rotation of a galaxy. The faster rotation in the outer areas can also be explained by the influence of dark matter.

 
 

One can only speculate about the structure of dark matter. The considerations range from
- not built from known elementary particles -
up to
- consists of non-luminous matter -
Such as:
Cold gas
Since hot gas always emits radiation, there is only one possibility left for dark matter cold gas left. Against this hypothesis speaks the fact that cold gas can (under certain circumstances) warm up and even huge amounts of gas could not generate the required mass. There are also no absorption lines that the gas would have to emit from objects behind.
Cold clouds of dust
A similar solution poses the possible existence cold clouds of dust that do not radiate due to their low temperature and would therefore be invisible. However, they would re-emit the light from stars and thus be visible in the infrared range. In addition, such large amounts of dust would be required that they would have had a significant impact on the formation of the stars.
MACHOs
(Massive astrophysical compact halo objects) These are celestial bodies in which the pressure is so low that nuclear fusion cannot take place, so that they are not visible. These can be, for example, brown dwarfs (too small stars without nuclear fusion) or old, extinguished and cooled stars.
However, if a MACHO is right in front of a star, it acts as a gravitational lens and amplifies its radiation. Indeed, this has been seen sporadically between Earth and the Large Magellanic Cloud. However, it is now believed that MACHOs make up only a small part of dark matter.