Scientists are challenging how quarks, believed to be at the core of neutron stars, behave in conditions of extreme pressure.
Their questioning is leading them just a bit beyond the edges of the periodic table, where a new form of matter with quarks behaving bizarrely, may exist.
What Are Quarks?
Atoms have protons and neutrons, two types of baryons. A baryon is a subatomic particle composed of three quarks bound snugly to each other, which cannot be unbound under normal conditions.
There are six types of quarks, and for some reason, they have such whimsical names. These include up, down, strange, charm, top, and bottom. Protons have two up quarks and one down quark, while neutrons have two downs and one up. It is possible to find baryons with different arrangements of quarks, but those are very rare.
Researchers at Toronto University believe they could be found in massive elements just sitting beyond the periodic table. Currently, the heaviest element in existence is oganesson, which has an atomic mass of 294. It is entirely possible to find a heavier element, but as atoms increase in mass, the more they defy the rules of physics.
Up-Down Quark Matter
Physicists Bob Holdom, Jing Ren, and Chen Zhang propose in a paper published in the Physical Review Letters that just beyond the periodic table is a form of matter with quarks that can break free of their triplet bonds and remain stable.
The researchers say that supermassive elements carrying an atomic mass above 300 could have free-flowing quarks. Called up-down quark matter or udQM, this new form of matter could potentially be harnessed to create a new source of energy.
The idea is not new. More than 30 years ago, physicist Edward Witten advanced the notion that a mix of free-flowing up, down, and strange quarks could keep their lowest energy state and remain stable if put under the right amount of pressure, the same kind that they would be put through at the heart of a neutron star.
This is called Strange Quark Matter where quarks are not bound in threes but flow freely as in a liquid. Witten's peers, however, dismissed the idea since up and down quarks appeared to work well enough together without throwing in some strange quarks into the mix.
The team at Toronto University believe that udQM, from an energetic standpoint, may be more favorable than SQM.
"What is the lowest energy state of a sufficiently large number of quarks?" says the researchers. "We argue that the answer is not nuclear matter or strange SQM, but rather udQM, a state composed of nearly massless up and down quarks."
Where To Find udQM
Scientists have long surmised that the supermassive, compact matter lying at the center of neutron stars is composed of heavy matter with a udQM ground state. In other words, the lowest energy state of matter at the heart of neutron stars is a state of free-flowing up and down quarks.
It is possible that heavy elements with an atomic mass over 300 can be fused together to set their quarks "loose and free," according to the researchers. However, they will have to find enough neutrons to complete the process.
If this is not possible, scientists can still harness udQM via cosmic rays streaming through the Universe and hitting the Earth.
"Physicists have been searching for SQM for decades," the researchers say. "From our re results, many searches may have been looking in the wrong place."