Scientists have discovered that there are three neutron starsborn in the fires of other exploding stars, have 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 from the Institute of Space Sciences (ICE-CSIC) in Barcelona, using European and American space telescopes that work with X-ray light.
A neutron star is the collapsed core of a massive star that has disappeared supernovaand can hold up to almost three times as much mass of our sun in a spherical volume about 11 kilometers wide. All that matter packed into such a small area means that neutron stars are among the densest concentrations of matter in the known universe, after black holes. To make this statement more relatable, consider how a tablespoon of neutron star material would be comparable to the mass of Mount Everest.
This extreme nature also means that the physics governing the interiors of neutron stars remains obscure. These objects are called neutron stars to begin with because their matter is so crushed that it is negatively charged electrons and positively charged protons are pressed together and overcome the electrostatic force between them to form an object full of only neutral neutrons. Deeper in a neutron star’s core, matter can be crushed to an even greater extent, creating exotic, never-before-seen particles such as hypothetical hyperons. Perhaps, scientists think, neutrons themselves can also be broken apart in a neutron star, creating a soup the universe‘s most fundamental particles: quarks.
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What happens in a neutron star is determined by the neutron star’s equation of state. Think of this as a script that determines the internal structure and composition of a neutron star based on things like its mass, temperature, magnetic field and so forth. The problem is that scientists have literally hundreds of options for what this equation of state could be. Because we can’t replicate Soil the conditions inside a neutron star, testing which model is right depends largely on matching it with what astronomical observations tell us.
Now, however, the discovery of three neutron stars with significantly lower surface temperatures compared to other neutron stars of similar age has provided an important clue, allowing researchers to rule out three-quarters of the possible models for the equation of state of neutron stars in one. heart attack. Two of the neutron stars are pulsars, which are rapidly spinning neutron stars that fire beams of radio jets at us. The third neutron star, in the Vela Jr supernova remnant, does not show pulsar behavior, but that may be because its radio jets are not pointing in our direction.
The neutron stars were detected at X-ray wavelengths by the European Space Agency‘S XMM-Newton telescope And NASA‘S Chandra X-ray Observatory.
“The extraordinary 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, an XMM-Newton scientist at the European Space. Agency, in a statement.
The hotter a neutron star, the more energetic the X-rays, and the energy of the X-rays from these three neutron stars tells us that it is quite cold for neutron stars. We say “chilly,” but the neutron stars are still exceptionally hot, with temperatures ranging from 1.9 million to 4.6 million degrees Celsius (3.4 million to 8.3 million degrees Fahrenheit). But given their young age, ranging from 840 to 7,700 years, based on the size and expansion rate of the supernova remnants around them, they are considered exceptionally cold. Neutron stars are born with temperatures of hundreds of billions or even a trillion degrees, and although 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. One of these is through thermal radiation from their surfaces allowing heat energy to escape in the cold room. The other is neutrino emission, which steals energy from a neutron star’s core, and is thought to be responsible for the rapid cooling of this particular neutron star trio.
However, how quickly neutron stars can 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 invoking a rapid cooling mechanism,” one of the researchers, Nanda Rea from the Institute of Space Sciences and Institute for Space Studies of Catalonia, said in the paper . rack. “Since enhanced cooling can only be activated by certain equations of state, we can rule out a significant portion of the possible models.”
And they didn’t just do it; the team estimates that three-quarters of all possible models can be discarded after this result. The researchers were able to determine this by calculating cool curves. These are basically graphs showing how neutron stars cool relative to time. The shape of the curve is strongly dependent on properties of the neutron stars, such as mass and magnetic field strength. Using machine learning, the team calculated the set of parameters that best describe each cooling curve, and then matched them to potential equations of state, seeing which ones still match and which ones can be discarded because they have no chance of matching the data.
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This process has narrowed the range of possible equations of state, but the findings are about more than just characterizing neutrons stars. Introduces the behavior of matter on a subatomic scale under intense pressure, extreme temperatures and crushing gravity quantum effects too. Scientists are currently missing one quantum theory of gravityand an equation of state for neutron stars could therefore put us on the path to quantum effects and high-quality onesgravity physics finally together as a single theory.
The findings are described in a paper published June 20 in the journal Nature Astronomy.