Astronomers have found a star cluster, our Galaxy is broken
Scientists have discovered a stellar stream consisting of the remnants of the ancient globular clusters are broken by the gravity of the milky Way two billion years ago. The study is published in the journal Nature.
A globular cluster is a sphere, consisting of hundreds of thousands and even millions of stars, bound by gravity and orbiting around the galactic nucleus. Our Galaxy has about 150 globular clusters. But the "field of stars", which was recently discovered by astronomers of the international consortium of S5 is very different from the usual and well-studied globular clusters in the milky Way.
Working for the Anglo-Australian telescope (AAT) located in the state of New South Wales in Australia and measuring the flow velocity of stars in the constellation of the Phoenix, they have revealed the remains of globular clusters, where the stars have much less heavy elements than in other similar formations.
"Once we figured out which stars belong to the stream, we measured the amount of elements heavier than hydrogen and helium — what astronomers call metallicity — presented in a press release, Lowell Observatory the words of the first author of the study Zhen Vanya (Zhen Wan) of the University of Sydney. — We were very surprised to find that the flow of the Phoenix has a very low metallicity. It is markedly distinguished from all other globular clusters in the Galaxy."
After the Big Bang in the Universe there was only hydrogen and helium. These elements formed the first generation of stars. In these and subsequent generations of stars were formed more heavy elements.
The composition of the stars reflects the galactic gas cloud from which it was born. More than previous generations of stars filled the material elements heavier than hydrogen and helium, the more "metricname" become stars of subsequent populations. Thus a very ancient, primitive star almost does not contain heavy elements.
Modern theories of star formation suggest that there is a minimum value of metallicheski required for the formation of globular clusters. But in the stream of the Phoenix that was below.
"We can trace the origin of stars, measuring different types of chemical elements that we find in them the same way we can trace the relationship of man with his ancestors through their DNA — explains the other study participant, Dr. Skyler Kujan from Lowell Observatory, one of the founders of the collaboration S5. — The most interesting remains of this cluster is that its stars have a much smaller number of these elements than any other we've seen. It's almost like to find someone with DNA that does not correspond to the person, whether living or dead. This raises questions about the history of cluster formation".
"It's like star archaeology, revealing the remnants of something old, accidentally discovered," explains Alexander G. (Alexander Ji), another author of the study from the Observatory of the Carnegie in Pasadena, USA.
The authors believe that the globular cluster, the remnants of which make up the flow of the Phoenix was destroyed a few billion years ago, but its stars in its chemical composition keep the memory of education in the very early Universe.
"Perhaps the flow of the Phoenix is the last of its kind the balance of globular clusters, which emerged in conditions radically different from the modern world," write the authors.
The researchers plan to continue observations, to find more similar residues in globular clusters and to better understand their evolution.