The interaction between a pulsar and a massive star resulted in a massive outflow of Gamma rays.

An international team of astronomers discovered a Gamma-ray binary system in our galaxy. This extremely rare celestial structure was found at a distance of about 5,000 light-years from the Earth. The researchers observed that a rapidly rotating neutron star was accelerating surrounding particles while it passed by the massive star it orbits once every 50 years. Jamie Holder, an Astrophysicist from the University of Delaware who was a part of the researching team, regarded the experience as a once-in-a-lifetime event.

The rarity of this binary system can be determined by the fact that scientists only know about 10 systems of this type where a neutron star is orbiting around a massive star. What makes it even more important is that the radio waves emitted by its neutron star can be measured by the scientists. This makes it only the second binary system that offers this information to humanity. It informs us about the accurate amount of energy being used to accelerate particles. The significance of this finding increases many times as scientists don’t know much in this regard. Holder praised the discovery by saying,

“You couldn’t ask for a better natural laboratory to study particle acceleration in a continually changing environment — at energies far beyond anything we can produce on the Earth.”

Pulsars have an incredibly strong magnetic field around them. Whenever a pulsar finds gas or dust in the vicinity of a massive star, an event of particle acceleration takes place. The collision between these particles and the surrounding material leads to the production of high-energy Gamma rays. These radiations emit flashes of blue light upon reaching the atmosphere of Earth. These flashes are only a few nanoseconds long so human eye is unable to detect them. However, advanced telescopes like MAGIC and VERITAS can see this light.

The first incident of detecting Gamma rays from this binary system was reported in 2008. In addition to that, pulses of Radio waves were also discovered. The frequencies of these radio pulse were used to determine the speed of the pulsar. This allowed the astronomers to determine when the neutron star will be closest to the massive star. They calculated that it will take happen on 13^th November 2017 after completing a 50-year cycle.

Consequently, the researching teams of both telescopes (MAGIC and VERITAS) started to monitor the pulsar’s orbit in September 2016. It took 12 months before the expected results began to unveil as the researchers detected a massive increase in the number of Gamma rays hitting the Earth’s atmosphere in September 2017. That was the time when things started to change pretty abruptly and something different was observed each day. Tyler Williamson, a 4^th-year Doctoral Student at the University of Delaware, described that phase of the research in the following words:

“I would wake up every morning and check and see if we had new data, then analyze it as fast as I could, because there were times where the number of gamma rays we were seeing was changing rapidly over a day or two.”

He mentioned that during the closest approach between both these stars, the number of Gamma rays (detected by the VERITAS telescopes) increased by 10 times within a few days. It was a bit surprising for him so he double checked all the information before sending the data to the collaborators. The fact that the observational data didn’t match with any of the predictive models added a bit more interest to the issue. Most of these models showed that a gradual increment in the number of Gamma rays will be observed when the pulsar comes closer to the massive star. Holder explained that what actually happened was a complete opposite of that. He said,

“But our recorded data showed a huge spike in the number of gamma rays instead. This tells us that we need to revise the models of how this particle acceleration is happening.”

Scientists believe that they need to solve this mystery of particle acceleration in order to improve their understanding of the universe. Despite the fact that Gamma-ray binary systems are not the most common source of accelerated particles, they can provide some useful insights into the acceleration mechanisms that produce them. Having said that, astronomers will have to wait for 50 years to study this system again.