Ivan Minchev of the Leibniz Institute for Astrophysics Potsdam (AIP), Germany, has led an international research team who have found out how to recover the birthplaces of stars.
One of the major aims of galactic archaeology is to reconstruct the history of how the Milky Way was formed. The newly found ability to recover the birthplaces of stars will help to achieve this aim.
Why is it difficult to locate the birthplaces of stars?
The phenomenon of radial migration, which is when stars in galactic discs wander away from their birthplaces, severely hampers galactic archaeology. The migration away from the birthplaces of stars makes it more different to infer the history of the Milky Way.
Radial migration is influenced by several factors. These factors include:
- The size and speed of the galactic bar
- The number and shape of spiral arms in the galactic disc; and
- The frequency of smaller galaxies colliding with the Milky Way during the past 10bn years, and their individual masses
How did the team find out the birthplaces of stars?
The research team found a way of recovering the history of galactic migration by using the ages and chemical composition of stars in the manner of archaeological artefacts.
The scientists used well-established facts about galactic archaeology as their basis for progress. Firstly, they knew that when stars are born at a particular time and in their specific position, they have a distinct chemical-abundance pattern. Secondly, that star formation in the galactic disc progresses outwards. They realised that if it is possible to precisely measure a star’s chemical composition and age using factors then its birthplace can be found without using any additional modelling assumptions.
They used a sample of approximately 600 solar-neighbourhood stars. These were observed at the European Southern Observatory’s (ESO) La Silla Observatory in Chile, using the high-resolution spectrograph HARPS instrument mounted on a 3.6 m telescope.
The scientists were able to discover that the birthplaces of stars were across the galactic disc, and that the older ones came from the central parts. They were able to find this using some precise measurements of age and iron content.
The future of galactic archaeology
Future research can now calculate the birthplaces of stars which are not in the original sample. One example is that the Sun is 4.6bn years old and from its iron content it can be estimated that it was born about 2,000 light years closer to the galactic centre than where it remains now.