Astronomers have discovered a completely new type of star explosion Micronova

(ORDO NEWS) — A newly discovered type of stellar explosion may help us better understand thermonuclear explosions on dead stars.

The new phenomena are called microns, and they occur on the surface of white dwarf stars that are actively absorbing material from a close binary companion. The accumulation of material on a white dwarf leads to a localized thermonuclear explosion – micron.

According to astronomers, these explosions burn from tens to hundreds of quintillion kilograms of stellar material in a few hours.

If this is hard to imagine, then, according to the researchers, this is equivalent to several billion of the Great Pyramids of Giza. Or, if you prefer another comparison, about a thousandth of the moon‘s mass.

“We have discovered and identified for the first time what we call the micronova,” says astrophysicist Simone Scaringhi of Durham University in the UK.

“This phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew this, but this discovery offers an entirely new way to achieve them.”

White dwarfs in close binary systems can function as machines for thermonuclear explosions. A white dwarf is a so-called “dead” star – the remaining destroyed core after the main sequence star ran out of fuel and ejected its outer material. Other stars of this type, belonging to different mass classes, include neutron stars and black holes.

This collapsed core is very dense. White dwarf stars have a mass 1.4 times that of the Sun and are packed into a sphere the size of the Earth. Many of them are found in binary systems.

In some rare cases – about 10 of them have been found in the Milky Way – binary systems approach so close that the white dwarf takes away material from its companion, which leads to the so-called recurrent nova.

As the two stars orbit each other, material – mostly hydrogen – is sucked away from the companion by the smaller, denser, more massive white dwarf. This hydrogen accumulates on the surface of the white dwarf, where it heats up.

Periodically, the mass becomes so large that the pressure and temperature at the bottom of the layer become sufficient for a thermonuclear explosion, as a result of which excess matter is ejected into space. This is the new star.

Mikronova, as Scaringi and his colleagues found, is a smaller version of this explosion.

Researchers first detected a micron-emitting white dwarf in data from the exoplanet-searching telescope TESS. TESS is optimized for finding very small changes in the brightness of stars with orbiting exoplanets; the passage of an exoplanet in front of a star causes very little obscuration.

In the TESS data, the team found a micron when they detected a brief burst of light from a white dwarf star, not a dimming.

This prompted the search for similar events in other white dwarfs. In total, they detected three outbursts, the third of which, after subsequent observations, led to the discovery of a previously unknown white dwarf star.

But the outbreaks were too small to be neoplasms, which are much more powerful and longer lasting. So the team set out to look for a scenario that could explain these observations. They concluded that the micron was the most likely explanation.

When a white dwarf with a strong magnetic field is in a tight binary system, it can suck material out of its companion. The magnetic field propels this material toward the white dwarf’s poles, where it accumulates and eventually causes an outburst similar (but smaller) to a typical white dwarf nova.

“For the first time, we have seen that hydrogen fusion can also occur locally,” says astronomer Paul Groot of Radboud University in the Netherlands.

“Hydrogen fuel may be contained at the base of the magnetic poles of some white dwarfs, so that the merger occurs only at these magnetic poles. This results in the explosion of micronuclear bombs, the force of which is about one millionth of that of a new star, hence the name micronova.”

This find could solve a decades-old mystery. One of the white dwarfs in the TV Columbae binary has been observed with similar outbursts over the past 40 years or so. Similar flares have been observed on other highly magnetized white dwarfs for many years. This explanation can finally tell us the reasons.

The find suggests that such outbursts could be quite common, but astronomers need to gather more observations to understand them more deeply.

“It just shows how dynamic the universe is,” Scaringi says. “These events can be quite common, but because of their rapidity, they are hard to catch in action.”


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