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Distribution of very dense groups of stars in the
Milky Way, called globular clusters, superimposed on a map of the Milky Way
compiled from data obtained with the Gaia Space Observatory. Each dot
represents a cluster of a few thousand to several million stars, as in the
insert image of the Messier 10 cluster. The color of the dots shows their
metallicity, in other words, their abundance of heavy elements relative to the
Sun. The C-19 stars are indicated by the light blue symbols. Credit: N. Martin
/ Strasbourg Astronomical Observatory / CNRS; Canada-France-Hawaii Telescope /
Coelum; ESA / Gaia / DPAC |
The sun is 98.5 percent hydrogen and helium, two light chemical elements, and the remaining 1.5 percent is made up of heavier elements including carbon, oxygen, and iron. Metallicity refers to a star's quantity of heavier elements, which changes from one star to the next.
It has now been discovered that the Milky Way has a
stellar structure made up entirely of stars with exceptionally low metallicity,
with a heavy element concentration 2,500 times lower than the sun. This is
significantly lower than any other star structure known in the cosmos.
This finding was produced by an international team
directed by a CNRS researcher at the Strasbourg Astronomical Observatory (CNRS
/ University of Strasbourg) and including scientists from the Paris
Observatory—PSL / CNRS) and the J-L Lagrange Laboratory (CNRS / Côte d'Azur
Observatory).
This cluster of stars is part of the Milky Way's C-19
stellar structure. Not only does this discovery cast doubt on our current
understanding and models of stellar grouping formation, which rule out the existence
of structures made entirely of such stars, but it also provides a direct window
into the very earliest ages of star formation and stellar structure development
in the distant past.
The low metallicity of the C-19 stars indicates that
they were formed only a short time after the cosmos was created, when heavy
elements were synthesized by consecutive generations of big stars.
References:
Nicolas Martin, A stellar stream remnant of a globular
cluster below the metallicity floor, Nature (2022). DOI:
10.1038/s41586-021-04162-2
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