After years of successful concealment, the most primitive stars outside our Milky Way galaxy have finally been unmasked. New observations using ESO’s Very Large Telescope have been used to solve an important astrophysical puzzle concerning the oldest stars in our galactic neighbourhood — which is crucial for our understanding of the earliest stars in the Universe.

Primitive stars are supposed to be very old with very less metal content. They are believed to have come into being at very early stage of the evolution of the universe, i.e. less amount of heavy elements were created. That’s why these stars are termed extremely metal-poor stars.

Cosmologists think that larger galaxies like the Milky Way formed from the merger of smaller galaxies. Our Milky Way’s population of extremely metal-poor or “primitive” stars should already have been present in the dwarf galaxies from which it formed, and similar populations should be present in other dwarf galaxies. “So far, evidence for them has been scarce,” says co-author Giuseppina Battaglia. “Large surveys conducted in the last few years kept showing that the most ancient populations of stars in the Milky Way and dwarf galaxies did not match, which was not at all expected from cosmological models.”

That means the best way to look for such stars would be in dwarf galaxies which reside just outside our galaxy. These are really for normal telescope reach. Yet there had been observations with multi-object instruments FLAMES. But it didn’t give any convincing results. The follow-up spectral observations on UVES and improved computational models, it has been possible to detect such objects. In last couple of decades there has been great improvement in theoretical models of almost any kind of stars, perhaps due to better computational facilities. But these news results are proving very valuable for the understanding of our galaxy and the early evolutionary stages of the universe.

The astronomers also confirmed the almost pristine status of several extremely metal-poor stars thanks to much more detailed spectra obtained with the UVES instrument on ESO’s Very Large Telescope. “Compared to the vague fingerprints we had before, this would be as if we looked at the fingerprint through a microscope,” explains team member Vanessa Hill.

Although observations are time-consuming, the future in this field looks very optimistic. There’s only need for a new quest!

Source: No Place to Hide: Missing Primitive Stars Outside Milky Way Uncovered.

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