by Scientists may be closer than ever to solving the mystery of what lies deep below the surface of dead ultramassive stars known as neutron stars.
A new computer analysis of neutron stars has shown that there is an 80% to 90% chance that these bodies have cores packed with free quarks, which are fundamental subatomic particles normally found only in other particles such as protons and neutron.
Protons and neutrons combine to form the nuclei of atoms, which are surrounded by electrons. But according to the team, if neutron star cores are full of free quarks, they would be composed of exotic matter called “cold quark matter.” And in a cold quark, individual protons and neutrons cannot exist. Therefore, atoms cannot exist. Only the quarks.
If true, this would make neutron stars like extremely massive atomic nuclei.
“It’s great to see concretely how each new neutron star observation enables us to deduce the properties of neutron star material more precisely,” research author Joonas Nättilä, who is about to become an associate professor at the University of Helsinki . , said in a statement.
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Neutron stars are born when stars with masses between 10 and 20 times that of the sun run out of the fuel necessary for the intrinsic nuclear fusion that takes place in their cores. This results in the elimination of the outward energy which, for millions or even billions of years, has kept the star stable against the inward pressure of its own gravity.
With gravity the winner in this cosmic tug of war, the core of a star begins to collapse. As this happens, the outer material of the star, where nuclear fusion is still taking place, is blown away in a supernova explosion.
This causes the core of the constellation with a mass of one to two times that of the sun to be condensed down to a width of only about 12 miles (20 kilometers).
This massive reduction in the size of the neutron star now creates matter so dense that if brought to Earth it would be just a block of sugar the size of a cube weighing about 1 billion tons. That’s a sugar cube that weighs as much as 3,000 Empire State Buildings.
So now, the question is, what is this very exotic material, found nowhere else in the universe, made of? And, more generally, can the conditions in the densest regions of these dead stars create a whole new phase of matter called cold quark matter in the void of protons and neutrons?
Scientists cannot visit neutron stars to sample this material; even the nearest neutron stars are about 400 light-years away, so the next best thing is to simulate the conditions beneath the stars’ surfaces using a powerful combination of actual astronomical data and supercomputers.
This new research used a type of statistical inference called Bayesian inference that calculates the probability of various model parameters by direct comparison with observational data.
This enabled the team to determine the limits of neutron star matter, leading the team to conclude the presence of cold quark matter to a high degree of probability. The mechanism also suggested the existence of a state of matter in neutron stars that is “non-nuclear,” in which quarks are allowed to be “unconfined” in protons, neutrons and other particles.
“Their constituent quarks and glues are instead freed from their typical color confinement and allowed to move almost effortlessly,” Aleksi Vuorinen, professor of theoretical physics at the University of Helsinki, said in the statement.
The team’s supercomputer simulations also suggest that there is less than a 20% probability that material inside neutron stars will rapidly change from nuclear matter to “quark matter,” almost like water changing to ice. Such a rapid change in the material of neutron stars could destabilize it in a way that could cause even a tiny quark to collapse to give birth to a black hole.
The research also suggested that the core of quark matter could be fully confirmed in the future with further analysis.
The key was to determine how strong the phase transition from nuclear matter to quark matter is, which can occur when gravitational sensors become sensitive enough to hear “tiny vibrations” in space -time arising from the last moment before two neutron stars. orbiting each other collide.
However, even with improved observational data, better models of neutron cores will still require an enormous amount of power and computing time.
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“We had to use millions of CPU hours of supercomputer time to be able to compare our theoretical predictions with observations and constrain the probability of a quark-matter core,” said Joonas Hirvonen, staff member and graduate student at the University of Helsinki in the statement.
The team’s research was published in December in the journal Nature Communications.
