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Scientists discover new type of cosmic explosion called ‘micronova’

The phenomenon was seen on the surface of three white dwarfs - remnants of dead suns - as they fed in each case on a companion.

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This artist’s impression shows a two-star system where micronovae may occur. (ESO via SWNS)

By Mark Waghorn via SWNS

An explosion powerful enough to destroy 3.5 billion Great Pyramids of Giza has been witnessed by astronomers.

The new type of thermonuclear blast - named 'micronovae' - sheds fresh light on the eruptions of stars.

The phenomenon was seen on the surface of three white dwarfs - remnants of dead suns - as they fed in each case on a companion.

They last for just a few hours - rapidly burning through a huge amount of stellar material.

The events could be commonplace throughout the universe - but are extremely difficult to observe.

An international team stumbled on them when noticing a brief, bright, flash of light while analyzing data from NASA's Transiting Exoplanet Survey Satellite (TESS).

Two were from already known white dwarfs, but the third needed more observations with an instrument on the European Southern Observatory's (ESO) Very Large Telescope (VLT).

Lead author Dr. Simone Scaringi, of 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."

Despite their immense force, micronovae are small on astronomical scales compared to novae and supernovae - which are extremely bright and have been known about for centuries.

There are numerous accounts across the history of 'new stars' being seen by astronomers which we now call novae.

In novae this thermonuclear explosion occurs over the entire surface. The intensely bright light can be seen for weeks.

Some supernovas, on the other hand, are so energetic they burn the entire white dwarf.

Both types occur on white dwarfs with a mass similar to that of our Sun - but as small as the Earth in size.

White dwarfs can steal material, mostly hydrogen, from their companion stars if they are close enough.

As the hydrogen falls on to the very hot surface of the dwarf star its atoms fuse into helium in an explosive fashion.

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

This artist’s impression shows a two-star system, with a white dwarf (in the foreground) and a companion star (in the background), where micronovae may occur. (ESO)

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

They occur on some white dwarfs with strong magnetic fields which funnel material towards the star's magnetic poles.

Co-author Professor Paul Groot, of Radboud University in the Netherlands, said: "For the first time, we have now seen that hydrogen fusion can also happen in a localized way.

"The hydrogen fuel can be contained at the base of the magnetic poles of some white dwarfs, so that fusion only happens at these magnetic poles.

"This leads to micro-fusion bombs going off, which have the strength of about one-millionth of a nova explosion, hence the name 'micronova'."

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

Dr. Scaringi said: "Rapid response from telescopes such as the VLT or ESO's New Technology Telescope and the suite of available instruments will allow us to truly unravel what these mysterious micronovae are."

The study in Nature was funded by the UK government's Science and Technology Facilities Council.

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