The unexpectedly fast cooling of three neutron stars, formed by supernova blasts, has given scientists new information about the strange nature of matter inside these vast objects.
Alessio Marino of the Institute of Space Sciences (ICE-CSIC) in Barcelona led this groundbreaking finding. It used information from X-ray-emitting space telescopes in Europe and the United States.
(Photo: Flickr/ Kevin Gill)
Neutron Stars and Their Harsh Conditions: What We Need to Know
Neutron stars are the collapsed cores of massive stars that have gone supernova. They are about 6.8 miles (11 kilometers) across and have up to three times the mass of our sun. Because of their very high density, neutron stars are among the densest things in the universe. Only black holes are denser. Consider Mount Everest, a tablespoon of neutron star material, to understand their thickness.
The method by which neutron stars are formed is by fusing protons and electrons under extreme pressure, which is the source of their name. Perhaps more unusual kinds of matter could exist in their cores, giving rise to quark matter or hyperons.
Mass, temperature, and magnetic fields can all be used to characterize neutron stars; a unique equation can also describe their internal structure. The way these stars act is determined by this formula. One has to research neutron stars to learn about the most unusual material in the universe, as scientists have found many different solutions to this equation.
The Discovery of Rapidly Cooling Neutron Stars
The researchers found three neutron stars whose surfaces were much cooler than those of other stars of the same age. Researchers can now rule out many possible models for the neutron star equation of state.
Two of these stars are pulsars, neutron stars that spin quickly and send out radiation beams. The third neutron star, which was found in the remains of the Vela Jr supernova, doesn't behave like a pulsar. Instead, its jets may be pointing away from Earth.
The XMM-Newton telescope from the European Space Agency and the Chandra X-ray Observatory found these neutron stars at X-ray wavelengths. They were surprisingly cold. Camille Diez, an XMM-Newton scientist at ESA, stressed that the XMM-Newton and Chandra telescopes' high sensitivity made it possible to find these neutron stars and gather enough light to figure out their temperatures and other important features.
These neutron stars are between 1.9 million and 4.6 million degrees Celsius hot, which is very hot but not very old, between 840 and 7,700 years. Other neutron stars of the same age are usually twice as hot, so this is different.
What this means for the Neutron Star Equation of State
Neutron stars cool down through heat radiation and neutrino emission. The neutrino emission causes these three stars to cool down so quickly. Some equations of state are needed to make the fast cooling mechanism work, which means that about 75% of current models can't explain these findings.
Nanda Rea from the Institute of Space Sciences pointed out that these three neutron stars look so young and have cold surfaces because of a rapid cooling process. Scientists are getting closer to finding the right equation of state for neutron stars thanks to this important rule out of possible models. This has huge implications for how we understand matter in very extreme conditions.
This study, published in the journal Nature Astronomy, not only narrows down the number of possible equations of state but also helps us learn more about the basic rules that govern the world. Scientists study these strange objects to find a link between quantum mechanics and general relativity. This could lead to new ideas explaining quantum effects and high-gravity physics.
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