December 8, 2023

Astrophysics: neutron stars that do not have foreign matter in their core

Astrophysics: neutron stars that do not have foreign matter in their core

The new findings now speak against the hypothesis. Strange as things are – she obviously isn’t acting totally weird after all. “It appears that these very strange states of matter do not exist in the core of a neutron star,” comments theoretical physicist Jorge Piekarewicz of Florida State University. Then, the phase transition into quark matter—if it exists at all—will occur only shortly before the critical limit from which the neutron star relentlessly collapses into a black hole. The exact value of this is unknown, and it is believed to be about three solar masses. “The question is, if you find a foreign substance at a high density, when exactly does it form?” Watts says.

If J0740 had gone through this transition and contained easily compressible quark material, it should have been nine to ten miles larger, according to Watts. But even if you take the uncertainty into account, according to Miller, a diameter of 22 kilometers would be a fairly obvious lower bound.

This means that if neutron stars produce quark matter at all, then only at some point does it exceed 2.1 solar masses. Protons and neutrons can be just as easily preserved even at the most extreme scales. “Anyway, it appears that some of the models are being left out now,” Watts comments.

Illustration of a radiation explosion on a magnetic starLaden…

© NASA’s Goddard Space Flight Center (Oceanite)

Breakout on the magnet | The illustration shows an outburst of radiation on a magnetar, a neutron star with a particularly strong magnetic field.

The fact that measurements of the size of neutron stars are possible mainly due to the peculiarity of celestial bodies. They spin quickly and spin patches on their surface, emitting strong magnetic fields that send X-rays into space. Because of the massive gravitational effect of compact objects, even radiation that originates on the opposite side of a neutron star is gravitationally bent and directed in our direction. With NICER, the arrival times of X-ray flashes can be recorded with high accuracy. This allows drawing conclusions about the diameter.

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