‘Stripped, pulsating core of a massive star’ spotted for the first time

A trio of researchers from the Friedrich-Alexander University of Erlangen-Nuremberg, the University of Innsbruck and the University of Geneva respectively have discovered a “stripped, pulsating core of a massive star” for the first time. In their article published in the magazine Natural AstronomyAndreas Irrgang, Norbert Przybilla and Georges Meynet, describe the unique object and the work they have done to verify its composition.

Stellar nuclei, as their name suggests, are the innermost parts of stars. Typically, such cores are covered by what space scientists call their “opaque envelope.” The theory has suggested that such nuclei may appear without their shells if conditions leading to their removal arise. But until now this had never been observed.

In their paper, the researchers write that their discovery of what was believed to be an average, normal star, called γ Columbae, was purely “accidental.” They looked at a group of stars and found that their data suggested that one of them was unusual. That led them to take a closer look at the light spectrum emitted by the star and in the process discover evidence of a missing envelope.

For such an object to exist, the researchers note, something must have stripped a normal star’s envelope and left its core. That would have made the object significantly smaller. They estimate that star γ Columbae was probably about 12 times the mass of the sun before it lost its shell – it is now only five times the size of the sun.

The researchers also note that spotting the unique object was really a matter of chance — pointing out that such an object wouldn’t last very long as a stripped core — perhaps only 10,000 years or so, a real blink of an eye in astronomical terms. . They also note that previous research suggests that before it was stripped, γ Columbae was likely an average massive star that probably ran out hydrogen.

That would have forced his envelope to expand, possibly a companion star, which could have resulted in the envelope being ejected. They note that the object is currently burning helium, but at some point it will begin to melt heavier elements until it explodes as a supernova with a stripped core, and then it will become a neutron star.

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