with help very large telescope (VLT) At the European Southern Observatory (ESO), a team of astronomers has observed a new type of starburst: a micronova. These explosions occur on the surface of some stars and can burn up about 3.5 billion Giza pyramids of stellar material within a few hours.
“We have detected and identified for the first time something we call a micronova,” explains Simon Scaringi, an astronomer at Durham University, UK, who led the study of these eruptions published in the journal Nature.
“This phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew this already, but this discovery offers us an entirely new way for this to happen,” he adds.
Micronovas are very powerful events, but they are also small events on an astronomical scale; They are much less active than starbursts known as novas, which astronomers have known for centuries. Both types of explosions occur in white dwarfs, which are “dead” stars with a mass similar to our Sun, but as small as Earth in terms of size, meaning they are very dense bodies.
A white dwarf in a binary system can “steal” material, primarily hydrogen, from its companion star if both are close enough to each other. When this gas falls on the superheated surface of the white dwarf star, the hydrogen atoms in helium fuse completely explosively. In supernovae, these thermonuclear explosions occur across the entire stellar surface.
“Such explosions cause the entire surface of the white dwarf to burn and glow brightly for several weeks,” explains study co-author Natalie Degenar, an astronomer at the University of Amsterdam in the Netherlands.
Micronovae are similar explosions, but they are smaller and faster, lasting only a few hours. They occur in some white dwarfs with strong magnetic fields, as material is directed toward the star’s magnetic poles.
“We have seen for the first time that hydrogen fusion can also occur in a local way. Hydrogen is found at the base of the magnetic poles of some white dwarfs, so that fusion occurs only at those magnetic poles,” said Paul Grote, co-author of the study and an astronomer at Radbound University in the Netherlands.
This causes fine fusion bombs to explode, about a millionth the force of a Nova explosion; Hence the name Micronova ”, continues Groot. Although “partial” indicates that these events are small, we should not be deceived: only one of these eruptions can burn approximately 20,000,000 billion kilograms of matter, i.e. The equivalent of 3.5 billion pyramids of Giza.
These new microstructures are challenging astronomers’ understanding of starbursts, and they could be more abundant than previously thought. “This shows how dynamic the universe is. These events can actually be very common, but because they are so fast, they end up being difficult to catch in the moment of action,” explains Scaringi.
The team first discovered these mysterious micro-eruptions when they were analyzing data from the TESS satellite (Transiting a satellite to survey the outer planets) from NASA. “By analyzing the astronomical data collected by TESS, we discovered something unusual: a flash of bright visible light lasting only a few hours. When we studied this phenomenon closely, we discovered many other similar signs,” says Degenar.
The team observed three micronovae using TESS: two in known white dwarfs and a third that requires further observations, collected using the X-shooter instrument mounted on very large telescope (VLT) from ESO, to confirm that it was also a white dwarf.
“With the help of the VLT, we found that all of these visible light flashes were caused by white dwarfs,” DeGeneres says. “This observation was crucial for us to interpret our results and for the discovery of Micronova,” Scaringi adds.
Micronova’s discovery joins the well-known repertoire of starbursts. The team now wants to capture more of these elusive events, which require large-scale examinations and rapid follow-up measurements. Scaringi concludes that “rapid response by telescopes such as the VLT or ESO’s New Technology Telescope and their complement of available instruments will allow us to investigate in more detail what these enigmatic microwaves really are.”