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Exotic star

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An exotic star is a hypothetical compact object in space. These stars are not made of normal matter. Normal matter consists of electrons, protons, neutrons, or muons. Instead, exotic stars are composed of exotic matter. This matter is held together by intense gravity. To prevent a total collapse, these stars rely on degeneracy pressure. This is a quantum property that pushes back against gravity. Scientists study these objects to understand the limits of physics.

One major type is the quark star. These stars form through a specific process of decomposition. Intense gravitational pressure causes neutrons to break apart. This process turns neutrons into their constituent quarks. The resulting star is smaller and denser than a neutron star. It may stay in this state forever if no mass is added. Some quark stars contain strange quark matter. These are specifically called strange stars. Edward Witten first proposed the idea of strange stars. He suggested they would act like one giant nucleon.

Another possibility is the electroweak star. This star uses the electroweak force to stay stable. The force converts quarks into leptons. This conversion releases massive amounts of energy. This energy creates radiation pressure. This pressure stops the star from collapsing inward. The core of such a star might be small. It could be roughly the size of an apple. However, that core would contain about two Earth masses. The temperature could reach 10 to the 15th Kelvin.

Boson stars are also a theoretical possibility. Most stars are made of fermions like protons. Boson stars are made of particles called bosons. These stars might be transparent and invisible. Their gravity is so strong that it bends light. This creates a shadow similar to a black hole. Rotating boson stars might have a torus shape. A torus is a shape like a donut. These shapes result from centrifugal forces. Scientists look for them using gravitational waves. The event GW190521 might have been a collision of two boson stars.

There are even more extreme theoretical models. Preon stars are made of hypothetical particles called preons. Preons might be the building blocks of quarks. These stars would have enormous densities. They would be heavier and smaller than neutron stars. Q-stars are another type of dense object. They might originate from a supernova or the Big Bang. They could be denser than even quark stars. Some theories suggest they could bend spacetime significantly. This might allow some light to escape their surface.

Some theories involve the very smallest scales of physics. Planck stars are linked to loop quantum gravity. They form when energy density reaches the Planck limit. At this point, a repulsive force may arise. This force comes from Heisenberg's uncertainty principle. This principle might prevent a singularity from forming. This would stop the star from becoming a black hole. Other ideas include dark stars and black stars. These involve different views of gravity and dark matter. They represent the cutting edge of theoretical science.

These exotic stars connect many different fields of study. They link particle physics with massive astronomy. Studying them helps scientists understand dark matter. Some models suggest boson stars could explain dark matter haloes. They also relate to the study of the Big Bang. These objects help us test how gravity works. They push the boundaries of what we know about the universe. Even though they are hypothetical, they guide our research.

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