Astronomers find new kind of stellar explosion called a 'micronova'

A newly-discovered kind of stellar explosion could be commonplace in the universe and may change our understanding of how eruptions in stars occur, astronomers have suggested.

A micronova is a blast that lasts for just a few hours, which makes it very difficult to observe.

These explosions take place on the surface of certain stars and can quickly burn through huge amounts of material – equivalent to around 3.5 billion Great Pyramids of Giza.

An international team of researchers, led by Durham University, observed the phenomenon in three white dwarfs – the remnants of dead stars – as they fed in each case on a companion star.

According to the scientists, their findings could lead to more micronovae being found and challenge what we know about how thermonuclear explosions occur in stars.

While micronovae are extremely powerful, they are small on astronomical scales compared to novae and supernovae, which are extremely bright and have been known about for centuries.

Throughout history there are numerous accounts of new stars being seen by astronomers which we now call novae.

Lead author Dr Simone Scaringi, in the Centre for Extragalactic Astronomy, Durham University, said: ‘We have discovered and identified for the first time what we are calling a micronova.

‘The phenomenon challenges our understanding of how thermonuclear explosions in stars occur.

‘We thought we knew this, but this discovery proposes a totally new way to achieve them.

‘It just goes to show how dynamic the universe is.

‘These events may actually be quite common, but because they are so fast they are difficult to catch in action.’

The researchers first came across the unusual micronovae when they noticed a bright flash of light lasting for a short time while analysing data from Nasa’s Transiting Exoplanet Survey Satellite (TESS).

They have since observed three micronovae using the satellite, which is normally used to look for planets outside of our solar system.

Two micronovae were from already known white dwarfs, but the third needed more observations with the X-Shooter instrument on the European Southern Observatory’s (ESO) Very Large Telescope (VLT) for its white dwarf status to be confirmed.

In novae, a thermonuclear explosion occurs over the entire surface of the star and the intensely bright light from this blast can be seen for weeks.

Micronovae are similar explosions that are smaller in scale and faster, lasting several hours.

The researchers hope to capture more of these elusive events, which will require large-scale surveys and quick follow-up measurements.

The research, published in Nature, was funded in the UK by the Science and Technology Facilities Council.

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