The Fornax Dwarf galaxy: Image credit ESO
18th February 2010.
When the mother of all explosions, the Big Bang, went off around 13 billion years ago, the very first stars to form in the newly born Universe were primitive in their make up. They were the very first generation of stars and inferior to a star like our Sun which is rich in heavy elements heavier than hydrogen and helium, such as gold and uranium. These first suns were very metal poor stars, containing only a thousanth of the heavier elements that are known to exist in the Sun.
As the Universe aged and expanded after the Big Bang, astronomers knew that larger stellar systems such as our Milky Way were formed from the convergence of smaller dwarf galaxies. Therefore these very old and primitive stars should be present in these dwarfs, and if the Milky way is made up from mergers of such galaxies then some of the oldest stars in the cosmos should be right here in the Milky Way for us to study.
But up to now they have been very elusive, keeping themselves scarce and offering little evidence. Large surveys have been done that involved studying the most ancient stars in the Milky Way, and finding that the results did not match the predicted results from stars found in dwarf galaxies.
But astronomers using the FLAMES instrument on the ESO Very Large Telescope have recently measured the spectra of 2,000 giant stars in the neighbouring dwarf galaxies of the Milky Way. The Carina Dwarf Galaxies, Sextans, Fornax, and Sculptor. Their measurements have shown that there is only a subtle difference of the chemical fingerprint between normal metal poor stars, and extremely metal poor stars. This is why they went undetected before.
If you want to make something intricate and complex, you had better start simple and work up…the universe is no exception. These stars are shining examples showing us the first steps on stellar evolution. Now they have been unmasked, astronomers can now seek them out and study them.
