Astronomers discovered a new genre stellar explosion that could be commonplace in the universe and may change our understanding of how star flares occur.
A micronova is a thermonuclear explosion that lasts only a few hours, making them extremely difficult to observe.
These explosions occur on the surfaces of certain stars and can each rapidly burn up an enormous amount of stellar material equivalent to approximately 3.5 billion Great Pyramids of Giza.
An international team of researchers, led by the University of Durham, UK, observed the phenomenon in three white dwarfs – the remains of dead stars – as they in each case fed on a companion star.
They say their discovery could lead to the discovery of more micronovae and challenge what we know about how thermonuclear explosions occur in stars.
The research is published in the journal Nature.
The team first discovered the unusual micronovae when they noticed a bright flash of light for a short period while analyzing data from NASA’s Transiting Exoplanet Survey Satellite (TESS).
In total, they have since observed three micronovae using TESS, normally used to search for planets outside our solar system.
Two micronovae originated from previously known white dwarfs, but the third needed more observations with the European Southern Observatory’s (ESO) Very Large Telescope (VLT) X-Shooter instrument for its white dwarf status to be confirmed. confirmed.
Lead author Dr Simone Scaringi, from Durham University’s Center for Extragalactic Astronomy, said: “We have discovered and identified for the first time what we call a micronova. The phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew, but this discovery offers a whole new way to do it. This shows how dynamic the Universe is. These events can actually be quite common, but because they’re so fast-paced, they’re hard to capture in action.
Micronovae are extremely powerful, but are small on astronomical scales compared to novae and supernovae, which are extremely bright and have been known for centuries. There are many accounts throughout history of “new stars” seen by astronomers that we now call novae.
In novae, this thermonuclear explosion occurs over the entire surface of the star, and the intensely bright light from this explosion can be seen for weeks. Some supernovas, on the other hand, are so energetic that they burn up the entire white dwarf.
Both types of explosions occur on white dwarfs, dead stars similar in mass to our Sun, but as small as Earth.
White dwarfs can steal matter, mostly hydrogen, from their companion stars if they are close enough to them.
When hydrogen falls on the very hot surface of the dwarf star, its atoms fuse explosively into helium.
In novae, this thermonuclear explosion occurs over the entire surface of the star, and the intensely bright light from this explosion can be seen for weeks.
Micronovae are similar, smaller, faster explosions that last for several hours.
The researchers say they occur on some white dwarfs with strong magnetic fields, which direct matter toward the star’s magnetic poles.
Study co-author Professor Paul Groot, from Radboud University, the Netherlands, said: “For the first time, we have now seen that hydrogen fusion can also occur from localized way.
“Hydrogen fuel may be contained at the base of the magnetic poles of some white dwarfs, so that fusion only occurs at these magnetic poles.
“This leads to the explosion of micro fusion bombs, which have the force of about one millionth of a nova explosion, hence the name ‘micronova’.”
The team now wants to capture more of these elusive events, which will require large-scale investigations and rapid follow-up action.
Scaringi added: “The rapid response from telescopes such as the VLT or ESO’s New Technology Telescope and the suite of instruments available will allow us to really find out what these mysterious micronovae are.”
The research was funded in the UK by the Science and Technology Facilities Council.
– This press release was originally published on the Durham University website