Astronomers accidentally spotted the exposed inner core of a “strange” star
The exposed core of a massive star has been spotted for the first time, a discovery described as purely “accidental” by the team that stumbled upon it.
Although the core stars where the vast majority of stellar energy is generated by the nuclear fusion of hydrogen into helium, they are usually obscured by the bright outer material surrounding them. Stellar cores are exposed only in rare and extremely short-lived circumstances.
Observing such a core in isolation could help astrophysicists better understand the nuclear processes that take place in the heart of stars and how stellar objects evolve.
The stellar core in question is exposed, a bright previously observed star called Gamma Columbae (γ Columbae). it has a mass between 4 and 5 times that of the Sun. The team that discovered its exposed nature thinks it was once part of a massive star with as much as 12 times the mass of the sun.
The nature of γ Columba was discovered by astronomers, including lead author Andreas Irrgang from the observatory of Dr. Karl Remeis and the ECAP working group at Friedrich-Alexander University Erlangen-Nürnberg, Bamberg, Germany, while observing a group of stars and discovered that one of them was unusual.
By further investigating the light spectrum emitted by this unusual star, astronomers discovered an increased amount of helium and nitrogen. As this nuclear ash is usually obscured by the outer stellar plasma, this indicates that the outer envelope of γ Columbae is missing.
“This is probably the most interesting factor of all, in terms of the scientific outcome, because all the cores are hidden in other stars and here we have one bare, exposed, and that will leave a very specific signal in its pulsations,” said Norbert Przybilla, head of the Institute. for astrophysics and particle physics at the University of Innsbruck and co-author of the study, in a statement (opens in new tab) to the motherboard. “We have to follow it.”
This led them to wonder what processes might have stripped γ Columbae of its outer layers, significantly reducing its radius and leaving it as a glowing core.
The team believes that the formerly great star may have recently finished fusing hydrogen to helium in its core with previous research also suggesting this to be the case despite not hinting at the exposed nature of γ Columbae’s core.
Completion of hydrogen fusion causes the star’s outer layers to ‘blow up’. If a binary star’s companion were to be drawn into this envelope width of stellar material, it could cause that material to be ejected.
The team suggests two alternative potential mechanisms that could leave the exposed core behind. The stripping of outer material by a feeding binary star or the evacuation of outer material by stellar winds to reveal cores, the latter of which is typically seen in the late stages of incredibly massive stars with masses between 20 and 25 times that of the sun.
Further study of γ Columbae will be needed to assess the true mechanism behind the revealed nature of the core as the star does not quite fit the parameters that fit these proposed mechanisms. “Having a bare stellar core of such a mass is unique so far,” Przybilla told Motherboard, adding that the star so far seems “strange.”
One thing astronomers are pretty sure about is that this stripped-down existence is a core phase of the γ Columbae life that will last only about 10,000 years. Although a long period of time in human terms, this is no more than the proverbial blink of an eye in cosmic terms.
This further indicates that the discovery of this discovered stellar core is indeed very accidental.
As for the future of this exposed core, the team said that γ Columbae is currently using helium to fuel nuclear fusion by creating heavier elements, which it will eventually begin fusing as well. When γ Columbae eventually runs out of nuclear fusion fuel, the energy that prevents the core from collapsing under the inward pressure of its own gravity will also cease.
This will lead to a gravitational collapse that will trigger a core-bare supernova and turn γ Columbae into a neutron star – a stellar remnant with the mass of the Sun condensed into a diameter about the size of an average city on Earth.
Astronomers suggest that a better understanding of γ Columbae could come from studying it asteroseismologya field of science that studies the oscillations of stars and how sound waves pass through the plasma that makes them to study the interior of stars.
The team’s research was published in the journal Natural astronomy (opens in new tab).
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