The Absolute Cosmos: Orbits of metal poor ancient stars in Milky Way prompt scientists to reassess evolution of our galaxy
Stars having little to no metal in their composition are thought to be the most ancient stars existing in our galaxy Milky Way. A new research has concluded that some of them move in previously unpredicted orbits.
This new study of the oldest metal poor stars of our galaxy may force scientists to rethink how the Milky Way has evolved over the time.
As scientists explain, metal poor stars are some of the rarest objects in Milky Way galaxy, they contain less than one thousandth quantity of iron which is found on our Sun.
Scientists studied 475 metal poor stars and found that about eleven percent of them orbit in the almost flat plane that is our galaxy’s disc. Very much like our Sun, they follow almost circular path.
This was certainly not expected, it will make scientists to rethink some of the basic ideas of our galaxy’s evolution.
All the previous studies had shown that metal poor stars were mostly restricted to galactic bulge and halo. However, this new study showed a notable amount of stars orbiting the disk itself.
According to scientists, in the last year, the view of our galaxy has considerably changed. This new discovery is not consistent with the earlier galaxy formation theories.
Even though metal poor stars contain a tiny fraction of iron compared to Sun, yet their orbits are very much same like Sun.
Scientists identified these metal poor stars by using : ANU’s SkyMapper and 2.3-metre telescopes, and the European Space Agency’s (ESA) Gaia satellite. Telescopes identified the low metal content and then satellites determine their orbits.
The findings revealed that these stars have different patterns of orbits. Many of these ancient stars had spherical orbits around the Milky Way’s halo.
Some others had wobbly and uneven orbits. These orbits are thought to be the result of two collisions with smaller galaxies occurred in past.
Some stars were found orbiting retrograde. About five percent of them appeared to be going out of Milky Way. And lastly there were remaining fifty or so with orbits aligned with Milky Way’s disk.
These results were put together by scientists from Australia, Italy, Sweden, United States and Germany. The results will account for future scenarios of galaxy formation and will change the ideas considerably.
For more information: Exploring the Galaxy’s halo and very metal-weak thick disk with SkyMapper and Gaia DR2