Neutron Star Subtypes

• Neutron star
  • Protoneutron star (PNS), theorized.
  • Radio-quiet neutron stars
  • Radio loud neutron star
    • Single pulsars–general term for neutron stars that emit directed pulses of radiation towards us at regular intervals (due to their strong magnetic fields).
      • Rotation-powered pulsar ("radio pulsar")
        • Magnetar–a neutron star with an extremely strong magnetic field (1000 times more than a regular neutron star), and long rotation periods (5 to 12 seconds).
          • Soft gamma repeater (SGR)
          • Anomalous X-ray pulsar (AXP)
    • Binary pulsars
      • Low-mass X-ray binaries (LMXB)
      • Intermediate-mass X-ray binaries (IMXB)
      • High-mass X-ray binaries (HMXB)
      • Accretion-powered pulsar ("X-ray pulsar")
        • X-ray burster–a neutron star with a low mass binary companion from which matter is accreted resulting in irregular bursts of energy from the surface of the neutron star.
        • Millisecond pulsar (MSP) ("recycled pulsar")
          • Sub-millisecond pulsar.
  • Exotic star
    • Quark star–currently a hypothetical type of neutron star composed of quark matter, or strange matter. As of 2008, there are three candidates.
    • Electroweak star–currently a hypothetical type of extremely heavy neutron star, in which the quarks are converted to leptons through the electroweak force, but the gravitational collapse of the star is prevented by radiation pressure. As of 2010, there is no evidence for their existence.
    • Preon star–currently a hypothetical type of neutron star composed of preon matter. As of 2008, there is no evidence for the existence of preons.

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Binary Neutron Stars

About 5% of all known neutron stars are members of a binary system. The formation and evolution scenario of binary neutron stars is a rather exotic and complicated process.

The companion stars may be either ordinary stars, white dwarfs or other neutron stars. According to modern theories of binary evolution it is expected that neutron stars also exist in binary systems with black hole companions. 

Such binaries are expected to be prime sources for emittinggravitational waves. Neutron stars in binary systems often emit X-rays which is caused by the heating of material (gas) accreted from the companion star. 

Material from the outer layers of a (bloated) companion star is sucked towards the neutron star as a result of its very strong gravitational field. 

As a result of this process binary neutron stars may also coalesce into black holes if the accretion of mass takes place under extreme conditions.

It has been proposed that coalescence of binaries consisting of two neutron stars may be responsible for producing short gamma-ray bursts. Such events may also be responsible for creating all chemical elements beyond iron, as opposed to thesupernova nucleosynthesis theory.

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Mengenal Bintang Neutron

A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. 

Such stars are composed almost entirely of neutrons, which are subatomic particles without net electrical charge and with slightly larger mass than protons. Neutron stars are very hot and are supported against further collapse by quantum degeneracy pressure due to the phenomenon described by the Pauli exclusion principle. 

This principle states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously.

A typical neutron star has a mass between about 1.4 and 3.2 solar masses (see Chandrasekhar Limit), with a corresponding radius of about 12 km.

In contrast, theSun's radius is about 60,000 times that. Neutron stars have overall densities of 3.7×10¹⁷ to 5.9×10¹⁷ kg/m³ (2.6×10¹⁴ to 4.1×10¹⁴ times the density of the Sun), which compares with the approximate density of an atomic nucleus of 3×10¹⁷ kg/m³. 

The neutron star's density varies from below 1×10⁹ kg/m³ in the crust, increasing with depth to above 6×10¹⁷ or 8×10¹⁷ kg/m³ deeper inside (denser than an atomic nucleus). This density is approximately equivalent to the mass of a Boeing 747 compressed to the size of a small grain of sand.

In general, compact stars of less than 1.44 solar masses – the Chandrasekhar limit – are white dwarfs, and above 2 to 3 solar masses (the Tolman–Oppenheimer–Volkoff limit), aquark star might be created; however, this is uncertain. Gravitational collapse will usually occur on any compact star between 10 and 25 solar masses and produce a black hole.

Some neutron stars rotate very rapidly and emit beams of electromagnetic radiation as pulsars.

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