When a star reaches the end of its life it dies in the most spectacular way, through an incredibly powerful and luminous explosion known as a supernova. These occur every 200–400 years and are visible from the Earth’s surface.
Using the European Southern Observatory’s Very Large Telescope (ESO VLT), a team of astronomers have now discovered a smaller type of cosmic explosion, called the micronova. Their work has been published in Nature.
Excitingly, the discovery of the micronova has improved our knowledge of nuclear reactions. During a supernova a white dwarf in a two-star system can steal material, especially hydrogen, from its nearby companion. As this gas connects to the hot surface of the white dwarf, it triggers the hydrogen atoms to fuse into the helium, causing a thermonuclear explosion across the entire surface of the star.
“Such detonations make the entire surface of the white dwarf burn and shine brightly for several weeks,” explains co-author Dr Nathalie Degenaar, an astronomer at the University of Amsterdam, in The Netherlands).
In comparison, micronovas are a similar type of explosion but on a smaller and faster scale. They occur when white dwarfs with strong magnetic fields siphon material towards the star’s magnetic poles, causing hydrogen fusion to happen in a localised way.
“This leads to micro-fusion bombs going off, which have about one millionth of the strength of a nova explosion, hence the name micronova,” says study co-author Professor Paul Groot, an astronomer at Radboud University, The Netherlands.
“What’s incredible is that these bursts are very fast; they only last 10 hours to half a day and then are gone,” says Dr Simone Scaringi of Durham University, UK, who led the discovery. This is compared to supernovas, which can be visible for months.
The discovery of these micronova events challenge our understanding of stellar explosions, where novae may occur more frequently and in more diverse ways, than previously thought.
“It just goes to show how dynamic the Universe is,”says Scaringi. “These events may actually be quite common, but because they are so fast they are difficult to catch in action.”
Qamariya Nasrullah holds a PhD in evolutionary development from Monash University and an Honours degree in palaeontology from Flinders University.
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