Scientists found three neutron starsStars born in the fire of other exploding stars cooled surprisingly quickly, bringing us closer to understanding the exotic nature of the matter in the cores of these extreme objects.
The discovery was made by a Spanish team led by Alessio Marino of the Institute of Space Sciences in Barcelona (ICE-CSIC), using European and American space telescopes powered by X-ray light.
A neutron star is the collapsed core of a massive star. supernovaand can contain up to almost three times mass of our sun in a spherical volume of approximately 6.8 miles (11 kilometers) in diameter. Cramming all of this matter into such a small space means that neutron stars are among the densest concentrations of matter in the known universe, second only to that of neutron stars. black holes. To make this statement more relatable, consider how a tablespoon of neutron star material can be compared to the mass of Mount Everest.
This extreme nature also means that the physics governing the interiors of neutron stars remains obscure. These objects were originally called neutron stars because their material was crushed to the point of being negatively charged. electrons and positively charged protons They squeeze together and overcome the electrostatic force between them, forming an object completely filled with neutral substances. neutrons. Deep within the core of a neutron star, matter can be crushed to an even greater extent, creating exotic, never-before-seen particles such as hypothetical hyperons. Scientists believe that perhaps neutrons could break apart and form a soup inside a neutron star. UniverseThe most fundamental particles of: quarks.
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What happens inside a neutron star is governed by the neutron star equation of state. Think of it as a playbook for determining the internal structure and composition of a neutron star based on things like its mass, temperature, and so on. Magnetic field and such. The problem is that scientists have literally hundreds of options for what this equation of state might be. Because we can’t copy Soil Testing which model is correct for the conditions inside a neutron star depends largely on matching them with what astronomical observations tell us.
But now the discovery of three neutron stars with significantly lower surface temperatures compared to other neutron stars of similar age has provided a major clue that allows researchers to eliminate three-quarters of the possible models for the neutron star equation of state at once. paralysis. Two of the neutron stars pulsarsrapidly rotating neutron stars fire beams of radio jets toward us. The third neutron star in the Vela Jr supernova remnant does not exhibit pulsar behavior, but this may be because the radio jets are not pointing in our direction.
Neutron stars detected at X-ray wavelengths. European Space Agency‘S XMM-Newton telescope And NASA‘S Chandra X-ray Observatory.
“The superior sensitivity of XMM-Newton and Chandra made it possible not only to detect these neutron stars but also to collect enough light to determine their temperatures and other properties,” said Camille Diez, XMM-Newton scientist at the European Space Center. The agency made a statement.
The hotter a neutron star is, the more energetic the X-rays are, and the energy of the X-rays from these three neutron stars tells us that, as neutron stars go, they are pretty cold. We say “cold,” but neutron stars are still incredibly hot; their temperatures range from 1.9 million to 4.6 million degrees Celsius (3.4 million to 8.3 million degrees Fahrenheit). However, they are considered exceptionally cold due to their young ages, ranging from 840 to 7,700 years, depending on the size and expansion rate of surrounding supernova remnants. Neutron stars are born with temperatures of hundreds of billions or even a trillion degrees, and as they cool, other neutron stars of similar age have temperatures twice as high, sometimes even hotter than that.
Neutron stars can cool through two mechanisms. The first is thermal radiation from their surfaces, which allows heat energy to escape into cold air. space. The other is neutrino Energy-stealing emission from the core of a neutron star is thought to be responsible for the rapid cooling of this particular neutron star trio.
However, how fast neutron stars will cool as a result of these mechanisms depends on the equation of state.
“The young age and cold surface temperature of these three neutron stars can only be explained by the introduction of a rapid cooling mechanism,” said Nanda Rea from the Institute of Space Sciences and the Institute for Space Research of Catalonia, one of the researchers. expression. “Since advanced cooling can only be enabled by certain equations of state, this allows us to exclude a significant fraction of possible models.”
And didn’t they do so; The team estimates that three-quarters of all possible models can be ignored after this result. The researchers were able to determine this by calculating cold curves, which are essentially graphs showing how neutron stars cool relative to neutron stars. time. The shape of the curve depends largely on the properties of neutron stars, such as mass and magnetic field strength; So, using machine learning, the team calculated the range of parameters that best described each cooling curve and then matched them to the potential. state equations to see which ones still match and which can be discarded because the chance of matching the data is zero.
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This process narrowed the range of possible state equations, but the findings are about much more than characterizing the neutron. stars. The behavior of matter under intense pressure, extreme temperature and crushing gravity at subatomic scales quantum There are also effects. Scientists are currently missing quantum gravity theoryand an equation of state for neutron stars thus brings us to quantum effects and highgravity Eventually physics came together as a single theory.
The findings are described in a paper published June 20 in the journal Nature Astronomy.