If you took some water and compressed it with a piston, it would shrink as the particles get pressed closer together.
You d reach a point where the atoms collapse and form an ultra-dense soup of neutrons and protons if you continued ramping up the pressure. The only location in the Universe where this occurs is neutron stars, the collapsed residues of burned-out stars, and it produces mind-blowing densities– one teaspoon of such material weighs numerous hundred billion kgs.
What would occur if you continued to increase the pressure still further? Not even astrophysicists know the response to that.
The density at the heart of neutron stars is three to five times greater than that of an atomic nucleus; its the greatest density achievable before a great void forms. Nobody knows what happens to matter at such severe densities.
One theory posits that the ultra-dense soup of protons and neutrons will break down into a soup of quarks and gluons– the most basic foundation of matter.
” Some researchers believe that quark phases will appear in the center of neutron stars,” states Shigehiro Nagataki of the RIKEN Astrophysical Big Bang Laboratory. “But its an opinion.”
A promising way to find whether this weird form of matter exists is by observing mergers of 2 neutron stars using gravitational-wave detectors.
There are two possibilities for how protons and neutrons would disintegrate into their constituent quarks throughout mergers if it does exist. They might go through a sharp transition, similar to liquid water develops into vapor at its boiling point at typical pressures. Or there might be a fuzzy transition, comparable to how water ends up being vapor at pressures above its crucial point.
Now, Nagataki and colleagues have stimulated mergers in between 2 neutron stars and calculated the gravitational waves that would be produced by them to explore the second possibility.
The frequency of the gravitational waves from neutron-star mergers typically depends upon how fast the neutron star rotates. Bigger neutron stars typically rotate slower, and vice-versa.
The group found that it ought to be possible to probe whether the quark stage exists in a neutron star by evaluating the frequency of its gravitational waves. If it does exist, the gravitational waves can also reveal how the quark phase appears.
While present gravitational-wave detectors cant find this, the next generation of detectors, which will be coming online in the next decade or so, ought to have the ability to.
” Its remarkable to believe we need to have the ability to identify the type of transition by finding gravitational waves,” says Nagataki.
Reference: “Merger and Postmerger of Binary Neutron Stars with a Quark-Hadron Crossover Equation of State” by Yong-Jia Huang, Luca Baiotti, Toru Kojo, Kentaro Takami, Hajime Sotani, Hajime Togashi, Tetsuo Hatsuda, Shigehiro Nagataki and Yi-Zhong Fan, 26 October 2022, Physical Review Letters.DOI: 10.1103/ PhysRevLett.129.181101.
Figure 1: Gravitational waves produced by mergers between 2 neutron stars could expose the development of totally free quarks through such mergers. Credit: NASAs Goddard Space Flight Center/CI Lab
Gravitational waves could expose whether the quark soup that existed in the early Universe is created in neutron-star mergers.
RIKEN researchers suggest that gravitational-wave signals from combining neutron stars might reveal the existence of ultra-dense quark-gluon matter. By replicating these mergers and examining the resultant gravitational waves, they propose that next-gen detectors, due within the next years, could validate this theory.
Obvious signatures in gravitational-wave signals from merging neutron stars ought to reveal what happens to matter at the severe pressures created during such mergers, calculations by RIKEN scientists forecast.