Indeed, the traces of uranium-238 in the star's atmosphere could have come from just one supernova.
The uranium-238 absorption lines are relatively easy to detect in metal-poor stars because they are not obscured by the strong absorption lines of other metals.
The half-life of uranium-238 is only 4.5 billion years, so it has had time to decay to about an eighth of its original abundance.
Accounting for our assumptions about the initial composition of stars, thorium-232 can only provide a rough estimate - 4 to 5 billion years each way - of the age of the universe.
Cayrel and colleagues hope that they will soon be able to date the universe even more precisely by measuring the relative line intensities more accurately.
In the initial state, the graph of daughter isotope to the third isotope versus parent isotope to the third isotope should result in a straight, horizontal line.
The process of evaluating the daughter product as a ratio against another isotope of the same element is a valid method because, when a mineral or rock forms from a homogenous state, the elements that are assimilated into crystalline formation are very restricted.
This is three times more accurate than the previous best estimate, which was based on absorption lines of thorium-232.
Thorium-232 has a half-life of 14 billion years - similar to our current best guess of the age of the universe, and this means it can only have decayed by about half.
The new estimate makes the universe 12.5 billion years old - give or take 3 billion years (R Cayrel et al 2001 Nature 409 691).
Cayrel and colleagues used the Very Large Telescope at the European Southern Observatory in Chile to measure the spectra of a very old star - known as CS31082-001 - near the edge of the Milky Way.
It has been established through extensive experimentation that radioactive decay occurs at a constant rate. In this case, the initial condition is the amount of daughter isotope in the rock when it was formed.
This amount is often unknown and is one of the downfalls of conventional radiometric dating.
This point of intersection gives the initial ratio of daughter to non-daughter isotopes, which would also be the ratio in a mineral that crystallized without any parent isotope present.