Gas cloud in the weighing pan
This result fits the data of earlier studies, the researchers conclude. There was also evidence of the presence of gas at temperatures in excess of one million degrees Celsius. "So we know the gas is around the galaxy, and we know how hot it is, " commented Gupta. "The big question is: how big is the cloud and how much mass does it possess?"
Again, Chandra, along with the X-ray Observatory XMM-Newton and the Japanese X-ray telescope Suzaku, provided a first answer? And the scientists are astounded: although the gas cloud is very thin, it contains a total mass of more than 10 billion suns, possibly even 60 billion suns. Thus, the mass of the gas cloud is of the same order of magnitude as the mass of all stars of the Milky Way taken together. display
How much matter is actually gathered there, astronomers can not yet say? for many reasons. For example, it is unclear what the ratio of oxygen to hydrogen is in the thin cloud, the latter appearing to be the dominant gas in the cloud. Also unclear is the actual size of the halo. The only certainty is that it is very extensive: "It could extend around the Milky Way for a few 100, 000 light-years or even further into the local group of galaxies in the neighborhood, " says co-author Smita Mathur, also of the Ohio State University.
Baryons desperately wanted
The new data may help explain the mystery of the missing baryonic mass? one of the great unsolved mysteries of the cosmos. Baryons are the particles that make up "normal", visible matter. The core particles protons and neutrons are included.
The Problem: If we sum up the baryonic mass of all stars, the interstellar gas and the dust in the galaxies of the cosmos, we come to a value that is not even half as high as the theoretical extrapolations. The team around Gupta now suspects that this missing baryonic mass hides in hot gas clouds like the one Chandra has now discovered in the Milky Way. Presumably, these clouds have been overlooked so far, since they have such a low density, so the conclusion of the researchers.