This also makes them very sensitive probes of their environments. Millisecond pulsars, which can be timed with high precision, have a stability comparable to atomic-clock-based time standards when averaged over decades. The globular cluster Terzan 5 contains 37 of these, followed by 47 Tucanae with 22 and M28 and M15 with 8 pulsars each. Currently there are approximately 130 millisecond pulsars known in globular clusters. This is consistent with the spin-up theory of their formation, as the extremely high stellar density of these clusters implies a much higher likelihood of a pulsar having (or capturing) a giant companion star. Many millisecond pulsars are found in globular clusters. But the nature of the other process remains a mystery. Thorsett ( UCSC) showed that different millisecond pulsars must form by at least two distinct processes. There has been recent evidence that the standard evolutionary model fails to explain the evolution of all millisecond pulsars, especially young millisecond pulsars with relatively high magnetic fields, e.g. The transfer of angular momentum from this accretion event can theoretically increase the rotation rate of the pulsar to hundreds of times per second, as is observed in millisecond pulsars. It is thought that the X-rays in these systems are emitted by the accretion disk of a neutron star produced by the outer layers of a companion star that has overflowed its Roche lobe. Millisecond pulsars are thought to be related to low-mass X-ray binary systems. For this reason, millisecond pulsars are sometimes called recycled pulsars. The leading theory for the origin of millisecond pulsars is that they are old, rapidly rotating neutron stars that have been spun up or "recycled" through accretion of matter from a companion star in a close binary system. Millisecond pulsars have been detected in radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The lowest mass stars are ejected, the remaining normal stars evolve, and the "recycling" scenario (3-4) takes place, creating many millisecond pulsars.Ī millisecond pulsar ( MSP) is a pulsar with a rotational period less than about 10 milliseconds. But in a densely packed globular cluster (2b). Accretion ends, the neutron star is "recycled" into a millisecond pulsar. This "accretion" speeds up the neutron star's spin. The Sun-like star eventually expands, spilling material on to the neutron star. The massive star explodes, leaving a pulsar that eventually slows down, turns off, and becomes a cooling neutron star. A massive supergiant star and a "normal" Sun-like star orbit each other. This diagram shows the steps astronomers say are needed to create a pulsar with a superfast spin.
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