Neutron stars are some of the densest objects in the universe, where regular matter becomes degenerate and turns into the most exotic states we have theorized. The actual details are yet to be confirmed, but due to shape similarities, researchers have begun to refer to these states as nuclear pasta. And according to a new paper, it is likely the hardest substance in the universe.
Using simulations to study the elastic properties of neutron star crusts, the researchers were able to conclude that the material inside it is up to 10 billion billion times more rigid than steel. Neutron stars are, after all, 100 trillion times denser than any material here on Earth. The results are published in Physical Review Letters.
The simulations required 2 million hours worth of processor time, which was conducted using a supercomputer. On a regular laptop, the simulations would run for 250 years.
"Our results are valuable for astronomers who study neutron stars. Their outer layer is the part we actually observe, so we need to understand that in order to interpret astronomical observations of these stars," lead author Matthew Caplan, from McGill University, said in a statement. "The strength of the neutron star crust, especially the bottom of the crust, is relevant to a large number of astrophysics problems, but isn't well understood."
The crust of neutron stars is believed to be solid, while the inside is described as being similar to liquid crystals. Forces between protons and neutrons organize the degenerate matter into round shapes (gnocchi), thin and long (spaghetti), or in sheets (obviously the lasagna). The layer of pasta in the crust is expected to be roughly 100 meters (330 feet) in depth and weigh about 1 percent of the mass of the Sun (or roughly 3,330 Earths). That’s one heavy bowl of pasta.
Neutron stars, in general, are exceptionally small, with an average radius of 12 kilometers (7.5 miles) and a mass 1.4 times our own star. The collapse that precedes a supernova is so energetic that it can compress that amount of mass into a small size.
"A lot of interesting physics is going on here under extreme conditions and so understanding the physical properties of a neutron star is a way for scientists to test their theories and models,” Caplan added. “With this result, many problems need to be revisited. How large a mountain can you build on a neutron star before the crust breaks and it collapses? What will it look like? And most importantly, how can astronomers observe it?"
Gravitational waves from neutron star collisions were detected last year for the first time. Research like this can help us better understand the details of what is being observed.