Four Irish astronomers were part of an international team of scientists who for the first time observed in detail particle acceleration from a cosmic explosion outside our solar system.

The team studied a nova explosion, which is an explosion from the surface of a white dwarf star, in August last year stemming from a binary star system called RS Ophiuchi.

A nova explosion occurs when the core of a white dwarf star, once a normal star, starts to suck gas from its nearby companion star until the gas build-up on its surface triggers an explosion.

Dr Jonathan Mackey, Prof Felix Aharonian, Dr Robert Brose and Dr Davit Zargaryan, all researchers at the Dublin Institute for Advanced Studies (DIAS), were members of this international team, which published its findings in the journal Science last week.

‘Profound consequences for astrophysics’

Using the High Energy Stereoscopic System (HESS) telescopes in Namibia, the team was able to observe with unprecedented detail the particle acceleration caused by the explosion in real time – which was found to be several hundred times higher than previously observed in novae.

“This discovery will have profound consequences for astrophysics, as it has changed our understanding of particle acceleration in our universe,” said Aharonian, who led the DIAS involvement in the international study.

Aharonian said that during the observations using the HESS telescopes, the team discovered that the particles produced from the eruption reached energy levels that “we thought would have been their maximum acceleration rate” based on a theoretical calculation.

Energy released from the explosion was also found to transform extremely efficiently into accelerated protons and heavy nuclei, which contributed to the particles reaching the record-breaking acceleration levels.

Irish contribution

DIAS was one of the founding members of the HESS telescope facility in Namibia almost 20 years ago. The imaging technique it uses, known as the Atmospheric Cherenkov Telescope technique, was pioneered by Irish scientists Neil Porter and Trevor Weekes in the 1960s.

Weekes led the team that made the first successful detection of supernova remnant Crab Nebula using this technique almost two decades later in 1989.

Mackey, who leads the high-energy astrophysics group at DIAS and was part of a team that created a theoretical model to interpret data from the recent observations, said that findings from this research “will be key in helping us to understand how cosmic explosions work”.

The next step is to study more nova explosions in the future to assess whether RS Ophiuchi was unusually energetic or whether all nova explosions generate similar levels of particle acceleration.

“Discoveries such as these show the value of investing in scientific research to help strengthen our understanding of the universe we inhabit,” Mackey said.

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