A team of astronomers spent almost a year wondering what exactly was the flash of light they caught coming from the corpse of a dead star . Now, in a study published in the journal Nature , experts confirm that it is a new type of stellar explosion called a “micronova”, which would be powerful enough to destroy the equivalent of 3.5 billion Pyramids of Giza or about one thousandth of the mass of the Moon.
“We have discovered and identified for the first time what we call a micronova ,” says astrophysicist Simone Scaringi of Durham University. “The phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew this, but this discovery proposes an entirely new way to achieve them.”
What is a micronova?
A new phenomenon for science. In most stellar explosions involving white dwarfs, the star is completely surrounded by a “shell” of hydrogen that burns intensely for weeks or months. Scientists believe that the micronova occurs when the white dwarf’s strong magnetic field corrals hydrogen near its poles. Remember that the Sun will become a white dwarf once it has burned all its fuel (something that will not happen for several billion years).
“For the first time, we have seen that hydrogen fusion can also occur in a localized manner,” says Paul Groot, co-author of the paper. “Hydrogen fuel may be contained at the base of the magnetic poles of some white dwarfs, so fusion only occurs at these magnetic poles .”
What energy do they unleash?
These extremely powerful explosions take place on the surface of certain stars and can quickly burn up large amounts of material, scientists say. They burn from tens to hundreds of quintillion kilograms of stellar material in just a few hours . Of course, despite the fact that they are still very powerful stellar explosions, they are small on astronomical scales if we compare them with novae and supernovae, which are much brighter and have been known for centuries. A micronova would therefore be a smaller version of the nova.
The two objects, the star and the already white dwarf, are so close to each other that the white dwarf extracts material from its companion. It steals part of its atmosphere and accumulates it on its surface. By fusing hydrogen into heavier elements, the rapid thermonuclear explosion occurs.
“Hydrogen fuel may be contained at the base of the magnetic poles of some white dwarfs, so fusion only occurs at these magnetic poles. This leads to the explosion of microfusion bombs, which have the force of about one millionth of a nova explosion, hence the name “micronova,” say the authors.
location
Researchers first encountered micronovae when they noticed a short-lived flash of bright light while analyzing data from NASA’s Transiting Exoplanet Survey Satellite (TESS). Since then, they have observed three micronovae using the satellite, which is normally used to search for exoplanets, worlds outside our solar system.
This finding suggests that bursts could be quite common and further evidence of how dynamic our universe is.
Astronomers hope to capture more of these elusive events, which will require large-scale surveys and fast-response follow-up measurements.
Referencia: Simone Scaringi et al, Localized thermonuclear bursts from accreting magnetic white dwarfs, Nature (2022). DOI: 10.1038/s41586-022-04495-6. www.nature.com/articles/s41586-022-04495-6
