Micronovae: The Newly Discovered Space Bombs

A team of astronomerswith the help of the European Southern Observatory’s Very Large Telescope (VLT), has observed a new type of stellar explosion called a micronova.

These space bursts are produced on the surface of certain stars, and each of them can burn about 3.5 billion Great Pyramids of Giza of stellar material in just a few hours.

“We have discovered and identified for the first time what we call a micronova –announce it’s a statement Simone Scaringi, an astronomer at the University of Durham (United Kingdom) who has directed the study on these explosions that is published in the journal ‘Nature’–. The phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew but this discovery proposes a totally new way to get them”Add.

Micronovae are extremely powerful events, but they are small on an astronomical scale; they are much less energetic than exploding stars known as novae, which astronomers have known about for centuries. Both types of explosions occur in white dwarfs, dead stars with a mass about that of our Sun, but as small as Earth.

A white dwarf in a two-star system can steal material, mostly hydrogen, from its companion star if they are close enough. When this gas falls on the very hot surface of the white dwarf star, it causes hydrogen atoms to explosively fuse into helium. In novae, these thermonuclear explosions occur across the entire stellar surface.

“These detonations cause the entire surface of the white dwarf to burn and glow for several weeks,” explains co-author Nathalie Degenaar, an astronomer at the University of Amsterdam in the Netherlands.

Micronovae are similar, smaller-scale, faster explosions that last only a few hours. They are produced in some white dwarfs with strong magnetic fields, which funnel material towards the star’s magnetic poles.

“For the first time we have seen that hydrogen fusion can also occur in a localized way. Hydrogen fuel may be contained at the base of the magnetic poles of some white dwarfs, so fusion only occurs at these magnetic poles,” says Paul Groot, an astronomer at Radboud University in the Netherlands and co-author of the study. study.

“This causes micro-fusion bombs to explode, which have a millionth of the force of a nova explosion, hence the name micronova,” Groot continues. Although ‘micro’ may imply that these events are small, make no mistake: a single such burst can burn up to 20,000,000 trillion kilos, or about 3,500 million Great Pyramids of Giza, of material”.

These new micronovae challenge astronomers’ understanding of exploding stars and could be more abundant than previously thought. “This shows how dynamic the Universe is. These events can be quite common, but being so fast they are hard to catch in action.”, explains Scaringi.

The team first stumbled upon these mysterious microbursts when analyzing data from NASA’s Transiting Exoplanet Survey Satellite (TESS). “In examining astronomical data collected by NASA’s TESS, we discovered something unusual: a bright flash of optical light that lasted for a few hours. Looking further, we found several similar signs.” explains Degenaar.

The team observed three micronovae with TESS: two were from known white dwarfs, but the third required additional observations with the X-shooter instrument on ESO’s VLT to confirm its white dwarf status.

“With the help of ESO’s Very Large Telescope, we discovered that all these optical flares were produced by white dwarfs,” says Degenaar. “This observation was crucial for interpreting our result and for the discovery of micronovae,” Scaringi adds.

The discovery of micronovae adds to the repertoire of known stellar explosions. The team now wants to catch more of these elusive events, which requires large-scale studies and rapid follow-up measurements.

“The rapid response of telescopes such as the VLT or ESO’s New Technology Telescope and the set of available instruments will allow us to unravel in more detail what these mysterious micronovae are”, concludes Scaringi.