Scientists have found that 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 inside the cores of these extreme objects.
The discovery was made by a Spanish team led by Alessio Marino of the Institute of Space Sciences (ICE-CSIC) in Barcelona, using European and American space telescopes working with X-ray light.
A neutron star is the collapsed core of a massive star that has died supernovaand can contain up to three times the mass of our sun in a spherical volume only about 6.8 miles (11 kilometers) wide. All this matter packed into such a small area means that neutron stars are among the densest concentrations of matter in the known universe, second only to 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 interior of neutron stars remains obscure. These objects are originally called neutron stars because their matter has been shredded to such a degree that they are negatively charged electrons and positively charged protons join together, overcoming the electrostatic force between them to form a purely neutral object neutrons. Deeper in the core of a neutron star, matter can be compressed to an even greater extent, forming exotic, never-before-seen particles like the hypothetical hyperons. Perhaps, scientists believe, or the neutrons themselves can split up inside a neutron star, creating a soup of UNIVERSEthe most basic particles: quarks.
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What happens inside a neutron star is governed by the neutron star’s equation of state. Think of it as a playbook that determines the structure and internal composition of a neutron star based on things like its mass, temperature, magnetic field and so on. The problem is that scientists have literally hundreds of options for what this equation of state could be. Since we cannot repeat earth conditions inside a neutron star, testing which model is correct depends very much on how well they fit what astronomical observations tell us.
However, now the discovery of three neutron stars with significantly lower surface temperatures compared to other neutron stars of similar age has provided a big clue, allowing researchers to rule out three-quarters of the possible models for the equation of the state of neutron stars in one. stroke Two of the neutron stars are the pulsars, which are rapidly spinning neutron stars that shoot radioactive beams at us. The third neutron star, in the supernova remnant Vela Jr, does not exhibit pulsar behavior, but this may only be because its radio jets do not point in our direction.
Neutron stars were discovered at X-ray wavelengths by European Space AgencyS ‘ The XMM-Newton Telescope AND NASAS ‘ Chandra X-ray Observatory.
“The excellent sensitivity of XMM-Newton and Chandra made it possible not only to detect these neutron stars, but to collect enough light to determine their temperatures and properties,” said Camille Diez, who is an XMM-Newton scientist. in the European Space. The agency, in a statement.
The hotter a neutron star is, the more energetic its X-rays are, and the energy of the X-rays from these three neutron stars tells us they’re pretty cool as neutron stars go. We say “cold,” but neutron stars are still extremely hot, with temperatures ranging from 1.9 million to 4.6 million degrees Celsius (3.4 million to 8.3 million degrees Fahrenheit). However, for their young ages, ranging from 840 years to 7,700 years, based on the size and expansion rate of the supernova debris around them, they are considered extremely cold. Neutron stars are born at temperatures of hundreds of billions, or even a trillion degrees, and as they cool, other neutron stars of similar ages have temperatures twice as high—sometimes even hotter.
Neutron stars can cool via two mechanisms. One is through thermal radiation from their surfaces that allows heat energy to escape to the cold ROOM. The other is neutrino emission, which steals energy from the core of a neutron star, and is thought to be responsible for the rapid cooling of this particular trio of neutron stars.
However, how fast 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,” said one of the researchers, Nanda Rea from the Institute of Space Sciences and the Institute of Space Studies of Catalonia. statement. “Since enhanced cooling can only be triggered by certain equations of state, this allows us to rule out a significant number of possible models.”
And not only them; 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 cold curves, which are essentially graphs showing how neutron stars cool relative to time. The shape of the curve depends heavily on neutron star properties such as mass and magnetic field strength, so using machine learning, the team calculated the range of parameters that best describe each cooling curve and then matched these to the potential. equations of state, seeing which ones still match and which can be thrown out to have zero chance of matching the data.
This process has narrowed the range of possible equations of state, but the findings are about more than just characterizing the neutron. STARS. The behavior of matter on the subatomic scale under intense pressure, extreme temperature, and crushing gravity presents quantum and the effects. Scientists currently lack one quantum theory of gravityand an equation of state for neutron stars can put us on the path to bringing about quantum effects andgravity physics together as a single theory at last.
The findings are described in a paper published June 20 in the journal Nature Astronomy.
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