Image: Artur Plawgo via Getty Images
Scientists believe a well-known bright star in the southern sky is secretly a ‘unique object’ that has remained ‘hidden in plain sight’ until now, a discovery that could offer unprecedented insight into the mysterious innards stars, reports a new study.
Gamma (γ) Columbae, a star located about 870 light-years from Earth, has long been classified as a typical massive star. Now scientists have reversed that view by suggesting that γ Columbae is the “stripped pulsating core of a massive star” – meaning its atmosphere has been stripped away to expose the nuclear fusion factory at the center of the star – according to a study published Monday in natural astronomy.
The discovery of γ Columbae’s secret identity was “a coincidence”, said Norbert Przybilla, director of the Institute for Astrophysics and Particle Physics at the University of Innsbruck and co-author of the study, during a call with Motherboard. “We were just analyzing a lot of stars. At first glance, one wouldn’t expect the star to be anything special, but then, from a more detailed analysis, it immediately became clear that it’s something we don’t have. not seen so far.
“It’s always surprising what you find if you look closer and closer,” he added.
Przybilla and his colleagues found telltale signatures in the light spectrum of γ Columbae that indicate chemical abundances consistent with a star that has lost its outer atmospheric envelope. The team hypothesized that this gaseous veil was likely ripped off by an unseen companion star close to γ Columbae, or possibly merged with it in recent years.
As a result, γ Columbae went from a “normal” star that had about 12 times the mass of the Sun to a bare core that is about five times more massive than the Sun. Astronomers can sometimes glimpse details of the cores of extremely massive stars in their later stages, called Wolf-Rayet stars, or the cores of “sub-dwarf” stars of a scale similar to the Sun, but γ Columbae is the first exposed nucleus in this mass range that has already been spotted. This makes the star “a unique test bed for (binary) stellar evolution, hitherto hidden in plain sight,” according to the study.
“Having a bare stellar core of such mass is unique so far,” said Przybilla, who called it “weird.”
“We have through Wolf-Rayet stars insights into what the cores of very massive stars look like, and through sub-dwarf stars we know what the cores of low-mass stars look like, but in the middle , in between, so far we don’t have We don’t have a lot of evidence,” he said. “It’s the first step.”
Przybilla and his colleagues suggest that γ Columbae is currently going through a transitional phase of imbalance that will be incredibly brief, likely lasting only 10,000 years. Prior to this stage, γ Columbae was a regular massive star that no longer had hydrogen fusion in its core, prompting its outer gaseous layers to expand and encompass a companion star in a common atmospheric envelope. The instabilities resulting from this interaction then triggered the ejection of the envelope, and eventually a merger between the two stars.
What remains is the incredibly hot center of the star, which is likely burning through helium at this point. The star will eventually regain its balance by becoming an extremely hot core that will fuse heavier elements together for another million years or two, before ending its life in a dramatic type of stellar explosion called a core-collapse supernova. bare. After that, the star will enter a long afterlife as an extremely dense type of remnant called a neutron star.
It’s “very unique” to “find an object in this phase, because it’s only a few thousand years old, probably – a long time for us humans, but on astronomical, very, very short timescales,” he said. Przybilla. “It will always remain as a particular object.”
For this reason, γ Columbae offers an unprecedented window into the fundamental forces that power stars, with the potential to unlock answers to a host of questions in astrophysics. In particular, the object may provide information about the evolution of binary star systems, which may have more complicated lives than single-star systems, such as our solar system. Przybilla and his colleagues suggest that asteroseismology, which is the study of oscillations inside stars, would be particularly useful for probing the structure of the star.
“If you analyze earthquakes, you can really look at the Earth and how it’s built inside, and that has to be done with γ Columbae,” Przybilla said. “I think we’ll have a very, very good idea of what such a core looks like inside.”
“That’s probably the most interesting factor of all, in terms of scientific output, because all the nuclei are hidden in the other stars and here we have one that’s bare, bare, and will leave a very particular signal in its pulsations. .,” he concluded. “We have to follow that.”