THE discovery of magnetic 鈥渇ossils鈥� around young stars in the Milky Way has boosted the case for the existence of magnetic fields right after the big bang.
If primordial magnetic fields existed, they would have influenced how the universe evolved. For instance, they could have skewed its expansion in one direction.
Now, Claude Catala of the Paris Observatory in France and colleagues believe they have found 鈥渇ossils鈥� of primordial magnetic fields. The team were attempting to answer a puzzle in astronomy: why a small fraction of so-called main sequence A/B stars have very strong and ordered magnetic fields. These could have formed via two methods: a dynamo mechanism, due to their rotation, or by inheriting fossil fields that existed in the interstellar medium, the gas and dust between stars.
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The team focused on the precursors to such stars, known as HAeBe stars, which are in a stage of evolution in which gas and dust is still collapsing into the star due to gravity. As these stars are very faint and scarce in our galaxy, it has been impossible to detect and measure magnetic fields in these stars before, says Catala.
The astronomers used the Canada-Hawaii-France Telescope on Mauna Kea in Hawaii to measure the splitting of the HAeBe stars鈥� spectra by their magnetic fields and found they have fields of a few hundredths of a tesla ().
This rules out the dynamo mechanism, as these young stars have not existed long enough to generate their own fields, so they must have come from elsewhere. 鈥淭his is completely in agreement with the fossil field theory,鈥� says Catala. However, he adds that the team is not entirely sure of their origin, 鈥渂ut it could indeed be primordial鈥�.
鈥淭he fossil magnetic fields found around these young stars could indeed be primordial鈥�
Francesco Miniati at the Swiss Federal Institute of Technology, Zurich, says that while the study agrees with the fossil field theory, it does not prove that primordial magnetic fields existed. 鈥淚t would if we also knew that these stars were primordial first stars, which they are not,鈥� says Miniati. Catala agrees, but says that there is no telescope, existing or planned, that could see the first primordial stars, as they would be billions of light years away.
