Amateur astronomers help capture stellar explosion close to cosmic speed limit

 Amateur astronomers help capture stellar explosion close to cosmic speed limit 

By Emma Levy

It is fascinating that technology has the ability to discover new mysteries about the universe. These findings imply much for the future of astronomy.

A recurrent nova is born the same way that classical novae are. It comes from a white dwarf in a close binary system. The nova slowly accumulates hydrogen-rich material from a main sequence companion, and it then explodes. These recurrent novae explode more than once and repeat at regular intervals.  Last year the High Energy Stereoscopy System, or Hess, and the Cherenkov Telescope Array—a global network that is made up of five gamma-ray sensitive telescopes—observed one such massive explosion on the surface of a white dwarf star nova called. 

The observation was made by amateur astronomers, who saw that RS Ophiuchi—a recurrent nova about 5,000 light years away that had previously exploded in 1985, 2006, 2021, and 2021—had once again exploded. The astronomers quickly informed Hess that they had observed a cosmic explosion in which gamma rays traveled at close to cosmic speed. The research shows that the physical conditions around novae can approximate theoretical ideals. While this research is still ongoing, it is possible that novae could be a source of cosmic rays. Cosmic rays are a form of high-speed particles—either an atomic nucleus or an electron—that come from outside our solar system. While they come from white dwarfs, the acceleration observed could be just as strong as that from supernovae, which takes place at the death of a giant star, whereas a nova is an explosion on the surface of a white dwarf.

 

Fig 1. Illustration of explosions from RS Ophiuchi, at 5,000 light years away this nova explodes and becomes visible to the unaided eye. Source: NASA

The nova generates hourglass-shaped shockwaves. The waves push out into space and then compress stellar material, which is then energized and released as accelerating particles. These gamma rays are measured, and are still detectable for more than a month afterward. Those from RS Ophiuchi proved to be more energetic than any other nova seen before.

On August 8, 2021 RS Ophiuchi reached a magnitude of 4.5. The explosion proved so powerful that it could be seen by the naked eye. It was over a thousand times brighter than when it is quiescent—an inactive period—with a magnitude of 12.6. The figure below, Fig. 2, shows that data from the first five nights and the gamma-ray emissions from the direction of the novae. 

Fig 2. RS Ophiuchi significance maps, which were created from the Hess gamma-ray observations. “A” shows the early phases of the outburst and “B” shows the late phases of the outburst. Source: Science

The Cherenkov Telescope Array offers the possibility of new findings in the future. It will be used to help study other novae to see if they also have as  powerful accelerating particles as those from RS Ophiuchi. There are many implications for the future of what new discoveries could be made, but this one to say the least is revolutionary. 

Links:

https://www.independent.co.uk/space/amateur-astronomers-white-dwarf-explosion-b2033791.html 

https://www.science.org/doi/10.1126/science.abn0567 

https://www.sciencedirect.com/topics/physics-and-astronomy/recurrent-novae#:~:text=1.1%20Classical%20novae,undergo%20outburst%20more%20than%20once. 

https://apod.nasa.gov/apod/ap210822.html