Thermonuclear outbursts on dead stars have been a long-studied subject by astronomers. Scientists recently discovered a new explosion, similar to novae and supernovae, called the micronova. The addition of the micronova discovery challenges the idea of how thermonuclear explosions (or the death of stars) occur.
“We have discovered and identified for the first time what we are calling a micronova,” says astrophysicist Simone Scaringi of Durham University in the UK. “The phenomenon challenges our understanding of how thermonuclear explosions in stars occur. We thought we knew this, but this discovery proposes a totally new way to achieve them.”
On April 20, 2022, astronomers discovered the micronova with the help of the European Southern Observatory’s “Very Large Telescope” (ESO’s VLT). Yes, it is really called that. The telescope is located at the Atacama Desert in Chile, in the Paranal Observatory. It contains four large telescopes and four smaller telescopes, all of which are still operational. The telescope has made notable discoveries, including the first direct spectrum of an extrasolar planet, HR 8799c, the first direct measurement of the extrasolar planet, HD 209458b, and most recently, the micronova.
A micronova occurs when a white dwarf star pulls matter off of a nearby red giant until it reacts explosively. It is difficult to observe these reactions, however, as they last for a very short period of time compared to a nova. Micronovae are the smallest of the star explosions discovered thus far.
“For the first time, we have now seen that hydrogen fusion can also happen in a localised way. The hydrogen fuel can be contained at the base of the magnetic poles of some white dwarfs, so that fusion only happens at these magnetic poles,” says Paul Groot, an astronomer at Radboud University in the Netherlands and co-author of the study.
There are many other types of explosions, including novae, supernovae, and hypernovae. A nova occurs when a white dwarf star pulls matter off of a nearby red giant until a nuclear fusion occurs on the white dwarf star. The star, however, is not destroyed, and can actually happen multiple times, called a recurrent nova. There are two types of supernovae, which are both bigger than novae and micronovae.
Type I Supernovae happen when white dwarf stars pull matter from a nearby companion star (usually a red giant) until the dead star’s core re-ignites in a thermo-nuclear explosion that destroys the star. Similar to a nova but more powerful. Type II Supernovae occur when stars run out of nuclear fuel and collapse under their own gravity until they explode. There is hydrogen in this explosion, unlike in Type I Supernovae.
Hypernovae are extremely similar to supernovae and are sometimes called collapsars or superluminous supernovae. In order for a hypernovae to occur, the burst has to be 5-50 times more energetic than a supernova. These explosions, however, may or may not contain a powerful burst of gamma radiation.
A micronova has about 1/1,000,000 of the strength of a nova, which explains the name’s prefix of “micro.” While the event itself may seem small when scaled to a nova or supernova, the blast can still burn through roughly 20,000,000 trillion kg of material, which in comparison is about 3.5 billion Great Pyramids of Giza.
As scientists continue to study these newly discovered instances, telescopes continue to gather information on these phenomena. Hopefully, a micronova will be captured soon on camera from one of the various powerful telescopes that monitor stars. This discovery opens the door for learning more about the stars and their past and what really occurs when a star runs out of energy.
