Astronomers have captured a unicorn, the naked, pulsating core of a huge star
A star’s hot core, in which fusion reactions rage, is usually enveloped in additional layers of hot plasma and gas. Only very rarely does a star lose its outer layers, leaving only a bare core, which after a short time explodes as a supernova. The earliest known naked core of a massive star was Gamma Columbae in the constellation of Dove.
The core is the densest and hottest part of a star. In the core, thermonuclear fusion reactions take place and all the energy of the Sun is created there. It is usually hidden under the outer layers of the star, such as the convection zone or the photosphere. The theory is that in extreme cases the very nuclei of stars can appear if circumstances strip them of their outer layers. So far, no one has ever seen such a stripped core. They are like unicorns.
Andreas Irrgang. Credit: FAU.
Andreas Irrgang of Germany’s Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and his collaborators captured such a unicorn and traced the naked core of the star. They admit it was a total coincidence. They observed a group of stars and noticed that one of them, Gamma Columbae in the constellation of the Dove, was showing unusual data.
Logo. Credit: FAU.
They examined the star in question in more detail and were surprised to find that it appeared to be a core with no outer layers. It was originally a massive star that has lost its outer layers.
The bare core of a star does not appear alone. Originally, it must have been inside a massive star whose mass scientists estimate to be 12 Suns. It is now just a core that weighs only 4 to 5. Irgang et al. they surely have reason to be happy. Of course, naked star cores are extremely rare. For example, they appear at the end of a Wolf-Rayet star’s turbulent career blowing off its outer layers. Another thing is that the naked cores of stars in this form only exist for a very short time, at least on a cosmic scale. It will last for about 10 thousand years.
An astronomically short time, the original, massive Gamma Columbae ran out of available hydrogen and lost its outer layers. Now it is the core of the star itself that “burns” the helium. After some time, the fusion of heavier chemicals begins and explodes as a stripped-core supernova. Gamma Columbae eventually becomes a neutron star.
Literature
Nature Astronomy 31. 10. 2022.
