A newly discovered "left-handed" magnetic field that pervades the universe could help explain a long standing mystery - the absence of cosmic antimatter. A group of scientists, led by Tanmay Vachaspati from Arizona State University, with collaborators at Washington University and Nagoya University, announced their findings in Monthly Notices of the Royal Astronomical Society.
Planets, stars, gas and dust are almost entirely made up of "normal" matter of the kind we are familiar with on Earth. But theory predicts that there should be a similar amount of antimatter, like normal matter, but with the opposite charge. For example, an antielectron or positron has the same mass as its conventional counterpart, but a positive rather than negative charge.
NASA Fermi Gamma ray Space Telescope (FGST), launched in 2008, observes gamma rays (electromagnetic radiation with a shorter wavelength than X-rays) from very distant sources, such as the supermassive black holes found in many large galaxies. The gamma rays are sensitive to effect of the magnetic field they travel through on their long journey to the Earth. If the field is helical, it will imprint a spiral pattern on the distribution of gamma rays.
Vachaspati and his team see exactly this effect in the FGST data, allowing them to not only detect the magnetic field but to measure its properties. The data shows not only a helical field, but show that there is an excess of left-handedness - a fundamental discovery that for the first time suggests the precise mechanism that led to the absence of antimatter.
For example, mechanisms that occur nanoseconds after the Big Bang, when the Higgs field gave masses to all known particles, predict left-handed fields, while mechanisms based on interactions that occur even earlier predict right-handed fields.
According to the press release, Vachaspati commented: "Both the planet we live on and the star we orbit are made up of 'normal' matter, and though it features in many science fiction stories, antimatter seems to be incredibly rare in nature. With this new result, we have one of the first hints that we might be able to solve this mystery."
Reference:
The new work appears in "Intergalactic magnetic field spectra from diffuse gamma rays", Wenlei Chen, Borun D. Chowdhury, Francesc Ferrer, Hiroyuki Tashiro, and Tanmay Vachaspati, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.
Details of the earlier theoretical models appear in "Estimate of the Primordial Magnetic Field Helicity", Tanmay Vachaspati, Phys. Rev. Lett. 87, 251302, published 2001. A copy of the paper is available from https://arxiv.org/abs/astro-ph/0101261
