Europium is essential to understand the formation of heavy elements, resultant of the fast neutron capture process or r-process. It is crucial for both the formation of half the elements heavier than iron and all of thorium and uranium in the Universe. The EUROPIUM group has studied both theoretical astrophysical simulations with old star observations in the Milky Way and dwarf galaxies.
Dwarf galaxies are small in size and have dark matter in abundance, and orbit the Milky Way. They are ideal test objects for studying the fast neutron capture process, as 10-13-year-old metal-lacking stars exhibit an overabundance of r-process elements.
Neutron-rich event caused the enrichment
Studies have suggested that only a single neutron-rich event could have been the reason for enrichment in dwarf galaxies. The researchers in Darmstadt and Heidelberg have successfully determined the highest europium content ever observed. The team has named them “europium stars.”
These stars are situated in the Fornax dwarf galaxy that has high stellar content. The study also reports the first-ever observation of lutetium in a dwarf galaxy. Besides, it is also the largest sample of observed zirconium.
A very rare finding
The “europium stars” in the Fornax dwarf galaxy were formed right after an explosive production of heavy elements. Considering the abundance of high stellar metal, the r-process event must have taken place 4-5 billion years ago. This is a very rare finding, as the stars that are rich in europium are mostly much older. This proves that europium offers an insight into the origin of elements in the Universe at a very late time.
The r-process when two neutron stars merge or when massive stars explode gives birth to heavy elements. The EUROPIUM group has analyzed these two high-energy events and carried out detailed studies of element formation in such environments. However, due to uncertainties in the nuclear physics data, assigning the heavy elements to one of the environments is not possible.
