Department of Physics senior lecturer part of international research team rewriting our understanding of antimatter

23 May 2017
Galaxy M51A

JJ Eldridge, Senior Lecturer, Department of Physics is excited to have been part of the research team rewriting our understanding of how antimatter is formed in our Galaxy.

The team’s new study, published in Nature Astronomy journal, has discovered that where we see antimatter and the amount we see comes from a very different type of exploding star than originally thought.

Until recently, scientists believed that antimatter was formed after super-stars, 10 times the mass of our sun, exploded. However the idea came with some mystery attached, as it didn’t fully explain why antimatter electrons (called positrons) were not being produced in the right amount in the right place within our Galaxy.

This latest research has discovered that most antimatter is actually created when much smaller, remnant stars only a few times the mass of our sun, merge and explode.

“It is, in fact, small, weaker supernovae that make more antimatter in our Galaxy than the biggest stellar explosions,” JJ says.

“These weaker supernovae never get hot enough to make lots of heavy elements such as the nickel in normal supernovae.  Instead they create lots of radioactive titanium. This is the element that produces all antimatter as it decays to non-radioactive elements.”

The weaker explosions were first observed in 1991, but the research team had to rule a lot of other things out before reaching their conclusion. The findings confirm that supposedly insignificant, weaker supernovae explosions are responsible for nearly all the antimatter in our Galaxy, and shows that even faint, rare and old stellar explosions have an impact on galactic evolution.

It is a significant step forward in our understanding of astrophysics, because it challenges our models of how stars create new heavier elements over time and perhaps where some of the elements which make us up came from.

“What might be of interest to the average person is this research shows that two percent of the calcium in our skeletons and our teeth came from this type of weaker explosion,” JJ says.

The next step for researchers is to look at what other influence these explosions could have, such as where all the elements that make up the Earth, the Sun, the Galaxy and ourselves come from, and include this new source of elements in galactic evolution models.

The international research team comprised: Roland Crocker (project lead), Ashley Ruiter, Ivo Seitenzahl, Fiona Panther, Stuart Sim, Holger Baumgardt, Ana Moller, David Nataf, Lilia Ferrario, JJ Eldridge, Martin White, Brad Tucker and Felix Aharonian.

What is antimatter?


Scientists have long known of the existence of antimatter in the Universe. Antimatter are particles which are a mirror version of the normal matter particles that make up everything around us. Each matter particle has an antimatter particle which has the same mass but carries the opposite electrical charge and spin. When the two come into contact, they destroy each other and turn into energy.


Additional information:

Link to paper: Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations, Nature Astronomy

Ten things you might not know about antimatter