Scientists have made new estimates of the size of mysterious neutron stars, revealing that the ultra-dense stellar corpses are slightly larger than previously thought.
According to the new estimates, published on April 27 in the journal Physical Review Letters, neutron stars – the densest known objects in the universe other than black holes – have a radius between 8.2 and 8.9 miles (13.25 and 14.25 kilometers).
Previously, these stars were believed to be the remains of a giant supernova explosions, has a slightly smaller radius up to 12 km. In this relatively small radius (whichever you look at), an amount of matter is squeezed, which equals 1.4 solar masses. The sun, by comparison, has a radius of 695,508 km (432,169 miles).
The researchers made the new estimates not by measuring neutron stars directly, but by looking at the so-called “neutron skin” or outer layer of neutrons, surrounding the nucleus of lead atom.
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So, what does lead have to do with the size of neutron stars? Lead is one of the densest materials found naturally on Earth. Even if lead is almost as dense as neutron stars, scientists assume that the physical principles governing the structure of lead atoms must be similar to those behind the structure of neutron stars.
“There is no experiment we can do in the laboratory that can investigate the structure of the neutron star,” said Jorge Piekarewicz, a nuclear physicist at Florida State University and one of the authors of the recent article. said in a statement. “A neutron star is such an exotic object that we couldn’t recreate it in the lab. So anything that can be done in the lab to limit or inform us about the properties of a neutron star is very helpful.”
The recent work of Piekarewicz and his colleagues looks at results of an experiment called PREX (for Pb Radius Experiment, Pb being the chemical symbol for lead), done recently by physicists at the Thomas Jefferson National Accelerator in Virginia. The researchers investigated lead atoms with electron beams and found that the neutron skin of the lead isotope Pb-208 is 0.28 femtometers (0.28 trillion millimeters) thick, about twice the thickness predicted by theorists. That study was too published April 27 in the journal Physical Review Letters.
Neutron skins and neutron stars
Atoms generally contains positively charged protons, negatively charged electrons, and neutrons that have no charge. Protons are pressed into the atomic nucleus while electrons make up its outer shell. With neutrons, it’s a little more complex.
Heavier atoms, such as lead, usually have more neutrons. Some of these neutrons are compressed in the nucleus along with the protons, but not all fit there. The rest is pushed to the edge of the nucleus, where it forms what physicists call the neutron skin.
The most common isotope of lead, Pb-208, commonly used for experiments, contains 82 protons and 126 neutrons. Physicists know that the size of the skin correlates with the size of the atom. Piekarewicz thinks the same about the much larger and denser neutron stars.
“The size of that skin, as it extends further, is something that relates to the size of the neutron star,” Piekarewicz said in the statement.
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Piekarewicz added, however, that his estimates were quite preparatory, and more work and progress would be needed in ie technologyniko for scientists to really get proper hold of neutron stars.
“It pushes the boundaries of knowledge,” Piekarewicz said. “We all want to know where we came from, what the universe consists of and what the ultimate fate of the universe is.”
The NASA Neutron Star Interior Composition Explorer (NICER) telescope, mounted on the International Space Station since 2017, has enabled astronomers to make measurements of the size and mass of some neutron stars, but much of what astronomers assume about these mysterious objects, remains based. about theory.
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