Neutron star explains quantum quirk
10 Dec 2016 by Evoluted New Media
Researchers have observed for the first time quantum physics behaviour predicted 80 years ago.
Researchers have observed for the first time quantum physics behaviour predicted 80 years ago.
Astronomers from the European Southern Observatory (ESO) looked at RX J1856.5-3754 - a neutron star about 400 light years from Earth - using its Very Large Telescope (VLT). Due to the extreme magnetic fields these stars possess, they are able to affect the properties of empty space around them.
Professor Roberto Mignani, from INAF Milan and first author, explained: “According to quantum electrodynamics (QED), a highly magnetised vacuum behaves as a prism for the propagation of light, an effect known as vacuum birefringence.“
This effect was first predicted in a paper 80 years ago by Werner Heisenberg and Hans Heinrich Euler; however since then it has not been produced in laboratories. After analysis of the data collected, the researchers detected linear polarisation at a degree of around 16%. This is likely due to the boosting effect of vacuum birefringence around the neutron star.
Neutron stars are created when giant stars explode and their cores collapse, with protons and electrons compacted into neutrons due to extreme gravity. They are small – about 20km in diameter – and have a mass 1.4 times larger than that of our Sun. Neutron stars are able to have magnetic fields a million times stronger than the strongest ones found on Earth.
Associate Professor Roberto Turolla, from the University of Padua and a co-author, said: “Vacuum birefringence can be detected only in the presence of enormously strong magnetic fields, such as those around neutron stars. This shows, once more, that neutron stars are invaluable laboratories in which to study the fundamental laws of nature.”
The astronomers were able to carry out this research although it was at the limits of current telescope technology. Advances in technology mean the Extremely Large Telescope, currently being built at ESO, could enable polarisation measurements of other stars.
Professor Vincenzo Testa, from INAF Rome and co-author, said: “This is the faintest object for which polarisation has ever been measured. It required one of the largest and most efficient telescopes in the world, the VLT, and accurate data analysis techniques to enhance the signal from such a faint star.”
The study was published in Monthly Notices of the Royal Astronomical Society.
