Hubble revealed unusual blue ‘bubbles’ of younger stars

O astrophysicists working on the riddle of dark matter are looking dwarf galaxies containing dark matter, but which are likely too weak to have escaped previous detection. The standard cosmological model predicts the existence of a large number of these galaxies dwarfs around large galaxies like the Milky Way.

It is possible to hunt these dwarf galaxies, and more generally faint galaxies close to our galaxy using radio telescopes like those on the network very large matrix in New Mexico (USA). Technically speaking, it is about studying radiation radio of clouds of gasfor example through the famous line 21 cm of hydrogen. Several promising gas clouds that could be associated with faint dwarf galaxies were discovered by the group ofastronomers led by Elizabeth Adams of the Dutch Institute of Radio Astronomy.

These gas clouds were thought to be associated with the Milky Way and most of them probably are. But when teams — with researchers like David Sand, an associate professor of astronomy at UArizona, or Michael Jones, a postdoctoral researcher atArizona Steward Observatory and lead author of an article on these clouds and deposited in free access at arXiv — wanted to search stars associated with them and dwarf galaxies, they had surprises.

Thus, an unprecedented association of young blue stars forming a group called SECCO1 and observed with telescope Hubble was really ingalaxy cluster of the Virgin. Located at an estimated distance of between 48 to 72 millionlight-yearswas discovered by the famous French astronomer Carlos Messier (1730-1817) known for creating the famous catalog of deep sky objects named after him.

Two hypotheses for the origin of the mysterious “blue bubbles”

Other observations made with Hubble and the instruments of tram of Eso in Chile revealed the existence of ” bubbles similar plants with never-before-seen features. Thus, most stars in each system are very blue and very young, rich in heavy elements that astrophysicists call metals which are, in fact, simply different nuclei from those of thehydrogenI’helium and yours isotopesall bathed in clouds that contain very little atomic hydrogen forming at the very end of dwarf galaxy-sized structures.

the article about arXiv reports five blue “bubbles” that are distant from the Milky Way and distant galaxies in the cluster of Virginwith which they are potentially associated, at a distance of up to 300,000 light-years.

The presence almost exclusively of blue stars, therefore young, without yellow dwarf Where red dwarf actually detectable, indicates that star formation is recent. However, the presence of many metals indicates that the gas from which these stars were formed must have been in a large, ancient galaxy that had time to chemically evolve with several generations of stars performing. nucleosynthesis stellar and ending their lives in supernovae, thus ejecting the products of this nucleosynthesis into the galaxies. We must therefore see, as in the Milky Way, red dwarfs and yellow in abundance.

To resolve this paradox, two theories can be invoked, all involving pastas gas ejected from a large galaxy. The first takes the effect of tidal forces exerted by one large galaxy on another, forces that would therefore have stripped the gas. The other theory involves a galaxy rapidly colliding with a mass of hot plasma in the galaxy cluster. It can be shown that the shock produces a pressure capable of quickly ripping a mass of gas from the galaxy. We are talking about an effect called dynamic pressure stripping (ram pressure stripping in English).

The researchers lean more towards the second hypothesis because, in order to obtain bubbles despite everything being very isolated from the surrounding galaxies, they must move quickly, which is not compatible with the tidal mechanism hypothesis.

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