Phys.org - pulsar pulsar Like cosmic lighthouses sweeping the universe with bursts of energy, pulsars have fascinated and baffled astronomers since they were first discovered 50 years ago. In two studies, international teams of astronomers suggest ... 17 hours ago in Astronomy 1317 An analysis that would have taken more than a thousand years on a single computer has found within one year more than a dozen new rapidly rotating neutron stars in data from the Fermi gamma-ray space telescope. With computing ... Jan 11, 2017 in Astronomy 1289 Like anthropologists piecing together the human family tree, astronomers have found that a misfit "skeleton" of a star may link two different kinds of stellar remains. The mysterious object, called PSR J1119-6127, has been ... Jan 06, 2017 in Astronomy 55 A new discovery has upended the widely held view that all pulsars are orderly ticking clocks of the universe. A survey done at the Arecibo Observatory in Puerto Rico has fortuitously discovered two extremely strange pulsars ...

Jan 05, 2017 in Astronomy 46 A professional astrophysicist and an amateur astronomer have teamed up to reveal surprising details about an unusual millisecond pulsar (MSP) binary system comprising one of the fastest-spinning pulsars in our Galaxy and ... Dec 08, 2016 in Astronomy 1340 An international team of astrophysicists including Russian scientists from the Space Research Institute of the Russian Academy of Sciences (RAS), MIPT, and Pulkovo Observatory of RAS has detected an abrupt decrease of pulsar ... Nov 18, 2016 in Astronomy 34 Nov 15, 2016 in Astronomy report 596 Searching the universe for strange new star systems can lead to some pretty interesting finds. And sometimes, it can turn up phenomena that contradict everything we think we know about the formation and evolution of stars. ... Nov 08, 2016 in Astronomy 33 Neutron stars are the detritus of supernova explosions, with masses between one and several suns and diameters only tens of kilometers across.

A pulsar is a spinning neutron star with a strong magnetic field; charged particles ... Nov 07, 2016 in Astronomy 65 Nov 02, 2016 in Astronomy report 360 Next » Pulsar Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. For some pulsars, the regularity of pulsation is as precise as an atomic clock. Pulsars are known to have planets orbiting them, as in the case of PSR B1257+12.

Werner Becker of the Max Planck Institute for Extraterrestrial Physics said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work." This text uses material from Wikipedia , licensed under CC BY-SA pulsar - definition - What is ? What is ? pulsar definition : pulsar A pulsar (short for pulsating radio star) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range roughly from milliseconds to seconds for an individual pulsar. Pulsars are believed to be one of the candidates of high and ultra-high energy astroparticles (see also Centrifugal mechanism of acceleration). The precise periods of pulsars make them very useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation.

The first extrasolar planets were discovered around a pulsar, PSR B1257+12. Certain types of pulsars rival atomic clocks in their accuracy in keeping time. ==History of observation== ===Discovery=== The first pulsar was observed on November 28, 1967, by Jocelyn Bell Burnell and Antony Hewish. They observed pulses separated by 1.33 seconds that originated from the same location on the sky, and kept to sidereal time. In looking for explanations for the pulses, the short period of the pulses eliminated most astrophysical sources of radiation, such as stars, and since the pulses followed sidereal time, it could not be man-made radio frequency interference. When observations with another telescope confirmed the emission, it eliminated any sort of instrumental effects. At this point, Burnell notes of herself and Hewish that "we did not really believe that we had picked up signals from another civilization, but obviously the idea had crossed our minds and we had no proof that it was an entirely natural radio emission.

It is an interesting problem—if one thinks one may have detected life elsewhere in the universe, how does one announce the results responsibly?" Even so, they nicknamed the signal LGM-1, for "little green men" (a playful name for intelligent beings of extraterrestrial origin). It was not until a second pulsating source was discovered in a different part of the sky that the "LGM hypothesis" was entirely abandoned. Their pulsar was later dubbed CP 1919, and is now known by a number of designators including PSR 1919+21, PSR B1919+21 and PSR J1921+2153. Although CP 1919 emits in radio wavelengths, pulsars have, subsequently, been found to emit in visible light, X-ray, and/or gamma ray wavelengths. The word "pulsar" is a portmanteau of "pulsating star", and first appeared in print in 1968: The existence of neutron stars was first proposed by Walter Baade and Fritz Zwicky in 1934, when they argued that a small, dense star consisting primarily of neutrons would result from a supernova.

In 1967, shortly before the discovery of pulsars, Franco Pacini suggested that a rotating neutron star with a magnetic field would emit radiation, and even noted that such energy could be pumped into a supernova remnant around a neutron star, such as the Crab Nebula. After the discovery of the first pulsar, Thomas Gold independently suggested a rotating neutron star model similar to that of Pacini, and explicitly argued that this model could explain the pulsed radiation observed by Bell Burnell and Hewish. The discovery of the Crab pulsar later in 1968 seemed to provide confirmation of the rotating neutron star model of pulsars. The Crab pulsar has a 33-millisecond pulse period, which was too short to be consistent with other proposed models for pulsar emission. A rotation speed of 1,980 revolutions per minute was considered perfectly acceptable. Moreover, the Crab pulsar is so named because it is located at the center of the Crab Nebula, consistent with the 1933 prediction of Baade and Zwicky.

In 1974, Antony Hewish and Martin Ryle became the first astronomers to be awarded the Nobel Prize in physics, with the Royal Swedish Academy of Sciences noting that Hewish played a "decisive role in the discovery of pulsars". Considerable controversy is associated with the fact that Professor Hewish was awarded the prize while Bell, who made the initial discovery while she was his Ph.D student, was not. Bell claims no bitterness upon this point, supporting the decision of the Nobel prize committee. === Milestones === In 1974, Joseph Hooton Taylor, Jr. and Russell Hulse discovered for the first time a pulsar in a binary system, PSR B1913+16. This pulsar orbits another neutron star with an orbital period of just eight hours. Einstein's theory of general relativity predicts that this system should emit strong gravitational radiation, causing the orbit to continually contract as it loses orbital energy. Observations of the pulsar soon confirmed this prediction, providing the first ever evidence of the existence of gravitational waves. As of 2010, observations of this pulsar continue to agree with general relativity.

In 1993, the Nobel Prize in Physics was awarded to Taylor and Hulse for the discovery of this pulsar. In 1982, Don Backer led a group which discovered PSR B1937+21, a pulsar with a rotation period of just 1.6 milliseconds (38,500 rpm). Observations soon revealed that its magnetic field was much weaker than ordinary pulsars, while further discoveries cemented the idea that a new class of object, the "millisecond pulsars" (MSPs) had been found. MSPs are believed to be the end product of X-ray binaries. Owing to their extraordinarily rapid and stable rotation, MSPs can be used by astronomers as clocks rivaling the stability of the best atomic clocks on Earth. Factors affecting the arrival time of pulses at Earth by more than a few hundred nanoseconds can be easily detected and used to make precise measurements. Physical parameters accessible through pulsar timing include the 3D position of the pulsar, its proper motion, the electron content of the interstellar medium along the propagation path, the orbital parameters of any binary companion, the pulsar rotation period and its evolution with time.

(These are computed from the raw timing data by Tempo, a computer program specialized for this task.) After these factors have been taken into account, deviations between the observed arrival times and predictions made using these parameters can be found and attributed to one of three possibilities: intrinsic variations in the spin period of the pulsar, errors in the realization of Terrestrial Time against which arrival times were measured, or the presence of background gravitational waves. Scientists are currently attempting to resolve these possibilities by comparing the deviations seen between several different pulsars, forming what is known as a pulsar timing array. The goal of these efforts is to develop a pulsar-based time standard precise enough to make the first ever direct detection of gravitational waves. In June 2006, the astronomer John Middleditch and his team at LANL announced the first prediction of pulsar glitches with observational data from the Rossi X-ray Timing Explorer. They used observations of the pulsar PSR J0537-6910. In 1992, Aleksander Wolszczan discovered the first extrasolar planets around PSR B1257+12.

This discovery presented important evidence concerning the widespread existence of planets outside the Solar System, although it is very unlikely that any life form could survive in the environment of intense radiation near a pulsar. ==Nomenclature== Initially pulsars were named with letters of the discovering observatory followed by their right ascension (e.g. CP 1919). As more pulsars were discovered, the letter code became unwieldy, and so the convention then arose of using the letters PSR (Pulsating Source of Radio) followed by the pulsar's right ascension and degrees of declination (e.g. PSR 0531+21) and sometimes declination to a tenth of a degree (e.g. PSR 1913+167). Pulsars appearing very close together sometimes have letters appended (e.g. PSR 0021-72C and PSR 0021-72D). The modern convention prefixes the older numbers with a B (e.g. PSR B1919+21), with the B meaning the coordinates are for the 1950.0 epoch.

All new pulsars have a J indicating 2000.0 coordinates and also have declination including minutes (e.g. PSR J1921+2153). Pulsars that were discovered before 1993 tend to retain their B names rather than use their J names (e.g. PSR J1921+2153 is more commonly known as PSR B1919+21). Recently discovered pulsars only have a J name (e.g. PSR J0437-4715). All pulsars have a J name that provides more precise coordinates of its location in the sky. ==Formation, mechanism, turn off== The events leading to the formation of a pulsar begin when the core of a massive star is compressed during a supernova, which collapses into a neutron star. The neutron star retains most of its angular momentum, and since it has only a tiny fraction of its progenitor's radius (and therefore its moment of inertia is sharply reduced), it is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star.

The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation of the neutron star, which leads to the "pulsed" nature of its appearance. There are several types of pulsar (as described in the below section). In one type, the beam originates from the rotational energy of the neutron star, which generates an electrical field from the movement of the very strong magnetic field, resulting in the acceleration of protons and electrons on the star surface and the creation of an electromagnetic beam emanating from the poles of the magnetic field. This rotation slows down over time as electromagnetic power is emitted. When a pulsar's spin period slows down sufficiently, the radio pulsar mechanism is believed to turn off (the so-called "death line"). This turn-off seems to take place after about 10–100 million years, which means of all the neutron stars born in the 13.6 billion year age of the universe, around 99% no longer pulsate.

Though the general picture of pulsars as rapidly rotating neutron stars is widely accepted, Werner Becker of the Max Planck Institute for Extraterrestrial Physics said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work." ==Categories== Three distinct classes of pulsars are currently known to astronomers, according to the source of the power of the electromagnetic radiation: *Rotation-powered pulsars, where the loss of rotational energy of the star provides the power (as described in the previous section), *Accretion-powered pulsars (accounting for most but not all X-ray pulsars), where the gravitational potential energy of accreted matter is the power source (producing X-rays that are observable from the Earth). *Magnetars, where the decay of an extremely strong magnetic field provides the electromagnetic power. Although all three classes of objects are neutron stars, their observable behavior and the underlying physics are quite different. There are, however, connections. For example, X-ray pulsars are probably old rotationally-powered pulsars that have already lost most of their power, and have only become visible again after their binary companions had expanded and began transferring matter on to the neutron star.

The process of accretion can in turn transfer enough angular momentum to the neutron star to "recycle" it as a rotation-powered millisecond pulsar. As this matter lands on the neutron star, it is thought to "bury" the magnetic field of the neutron star (although the details are unclear), leaving millisecond pulsars with magnetic fields 1000-10,000 times weaker than average pulsars. This low magnetic field is less effective at slowing the pulsar's rotation, so millisecond pulsars live for billions of years, making them the oldest known pulsars. Millisecond pulsars are seen in globular clusters, which stopped forming neutron stars billions of years ago. ==Applications== The discovery of pulsars allowed astronomers to study an object never observed before, the neutron star. This kind of object is the only place where the behavior of matter at nuclear density can be observed (though not directly). Also, millisecond pulsars have allowed a test of general relativity in conditions of an intense gravitational field. ===Maps=== Pulsar maps have been included on the two Pioneer Plaques as well as the Voyager Golden Record.

They show the position of the Sun, relative to 14 pulsars, which are identified by the unique timing of their electromagnetic pulses, so that our position both in space and in time can be calculated by potential extraterrestrial intelligences. Because pulsars are emitting very regular pulses of radio waves, its radio transmissions do not require daily corrections. Moreover, pulsar positioning could create a spacecraft navigation system independently, or be used in conjunction with satellite navigation. ===Precise clocks=== Generally, the regularity of pulsar emission does not rival the stability of atomic clocks. However, for some millisecond pulsars, the regularity of pulsation is even more precise than an atomic clock. This stability allows millisecond pulsars to be used in establishing ephemeris time or in building pulsar clocks. Timing noise is the name for rotational irregularities observed in all pulsars. This timing noise is observable as random wandering in the pulse frequency or phase. It is unknown whether timing noise is related to pulsar glitches. ===Probes of the interstellar medium=== The radiation from pulsars passes through the interstellar medium (ISM) before reaching Earth.

Free electrons in the warm (8000 K), ionized component of the ISM and H II regions affect the radiation in two primary ways. The resulting changes to the pulsar's radiation provide an important probe of the ISM itself. Because of the dispersive nature of the interstellar plasma, lower-frequency radio waves travel through the medium slower than higher-frequency radio waves. The resulting delay in the arrival of pulses at a range of frequencies is directly measurable as the dispersion measure of the pulsar. The dispersion measure is the total column density of free electrons between the observer and the pulsar, : About Pulsars Home About Pulsars Technical Topics Software Articles Links Sitemap Contact About Pulsars A pulsar (short for pulsating radio star) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation which can only be observed when the beam of emission is pointing toward the Earth. A good analogy is a lighthouse whose light can only be seen when the lens is pointed in the direction of an observer, and gives a pulsed appearance to the steady light of the emitting light source.

The First Pulsar The first pulsar was observed on November 28, 1967, by Jocelyn Bell who observed pulses separated by 1.33 seconds that originated from the same location on the sky, and kept to sidereal time. The signal was nicknamed LGM-1, for "little green men" (a playful name for intelligent beings of extraterrestrial origin). It was not until a second pulsating source was discovered in a different part of the sky that the "LGM hypothesis" was entirely abandoned. The pulsar was later dubbed CP 1919, and is now known by a number of designators including PSR 1919+21, PSR B1919+21 and PSR J1921+2153. Neutron Stars Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses. Pulse periods range from roughly milliseconds to seconds and are unique to each individual pulsar. A neutron star is the product of the explosive transformation of a massive star.

Any star's life is a careful balancing act: the gravity of its own material pulls inward, while pressure from the heat and light produced by the burning of hydrogen into helium in the star's core pushes outward. For a massive star, this delicate dance goes on for millions of years, until the hydrogen supply in the core runs low. Gravity begins to take over and the core contracts and heats up. This increase in temperature allows the star to fuse helium into even heavier elements, temporarily staving off gravitational collapse. The cycle continues over millennia, with the star's core becoming increasingly hot and dense. In the innermost regions of the core, a mass of iron ashes begins to build up. This is the end of the line: iron cannot be fused into heavier elements without an input of energy. When enough iron accumulates within the core, it collapses rapidly. Electrons and protons are "squeezed" together to form neutrons. These neutrons temporarily but violently halt the collapse. In the process the outer layers of the star are blown off in a supernova, nature's most spectacular explosion. The remnant core, roughly twenty kilometers wide and densely packed with neutrons, is called a neutron star. Neutron stars are a study in extremes.

They weigh roughly twice as much as the sun but have a radius only 1/30,000 as great (which translates to a density roughly equivalent to that of an atomic nucleus). Any remnant rotational momentum of the original star results in a rapid spin-up of the collapsed neutron star, in much the same manner as an ice skater is able to spin-up by pulling their outstretched arms close to their chest. Apparent spin frequencies range from over 700 revolutions per second (42,000 RPM !!!) to just 1 revolution in 12 secs (5 RPM). The Vela Pulsar rotates at a moderate 672 RPM. Spin Frequency Stability For some millisecond pulsars, the regularity of pulsation is more precise than an atomic clock. This stability allows millisecond pulsars to be used in establishing ephemeris time or building pulsar clocks. It also allows a unique way of separating the pulsar signal out from other sources. Timing noise is the name for rotational irregularities observed in all pulsars. This timing noise is observable as random wandering in the pulse frequency or phase.

Spin Down Most pulsars exhibit a slow decay in spin frequency caused by energy loss through various mechanisms - especially rotational powered pulsars (pulsars can be powered by other mechanisms, e.g., mass accretion). This is an addition marker as other signals (e.g., earth-based RFI) are unlikely to exhibit the same change in frequency over time as a pulsar. However, it is important to note that 'glitches' are observed in the rotation velocity of many neutron stars. The rotational velocity is decreasing slowly but steadily, except by sudden variations. One model put forward to explain these glitches is that they are the result of "starquakes" that adjust the crust of the neutron star. Models where the glitch is due to a decoupling of the possibly superconducting interior of the star have also been advanced. In both cases, the star's moment of inertia changes, but its angular momentum does not, resulting in a change in rotation rate. The Vela Pulsar is a particularly 'glitch-prone' pulsar - with a sudden spin-up of the order of several ppm occurring, on average, every couple of years.

This means that, when using historical ephemeris data, that some adjustment should be made to account for the deviation from the simple spin-down model for the Vela Pulsar caused by those glitches. Dispersion The radio signals from a pulsar suffer dispersion as they travel through the ionized interstellar medium (ISM), resulting in a frequency dependent arrival time of the pulses. The effect is quantified by the pulsar’s dispersion measure (DM). Pulse arrival times are increasingly delayed when received at lower frequencies. In other words, pulses emitted at higher frequencies arrive earlier than those emitted at lower frequencies. As the receiving bandwidth is increased the difference between the arrival times for the lower frequencies and the higher frequencies in the passband increase. If that delay is not accounted for, the summed pulse will be blurred and smeared. If the delay is too big, the pulses may become undetectable. Scattering Electron distribution along the line of sight to the pulsar is not homogeneous throughout the interstellar medium, but it shows a certain "clumpiness". These clumps are large enough to scatter the radio waves into different paths. Due to this scattering, some rays can now make their way to the telescope which would otherwise have missed it.

These rays, however, have a longer path length and will therefore be slightly delayed compared to those signals which travel straight. The pulses become smeared again, showing an exponentially decaying tail and are therefore again more difficult to detect than without scattering. Scattering is heavily reduced at higher frequencies, e.g. it is a factor of 250 less severe at 1400 MHz than it is at 400 MHz. Scattering is strongest in those regions where we expect the largest densities of electrons, i.e. the Galactic plane and in particular the regions towards the Galactic Centre. Scintillation Scintillation can be observed visually as the twinkling of stars. They seem to change slightly in position and brightness moment to moment due to the effects of the atmosphere. The magnitude of this effect is proportional to the level of instability in the atmosphere. Likewise, radio sources can experience the same effect - but instead it is largely the ISM which is the source of the effect. It is caused, basically, by the constructive/destructive interference of signals scattered by the ISM. Diffractive Scintillation The observed effect on radio signals from pulsars is a variation in the strength of the pulses on timescales from minutes to hours.

Depending on the pulsar this can mean that a signal might be, at one instance, be much stronger than its long term average, or conversely, much weaker. It may mean that during an observation covering a few hours, the excision of periods where the pulsar has faded in strength from the data record, whilst keeping the enhanced portions, can mean an improvement in S/N. Also the range of frequencies (decorrelation bandwidth) over which this interference occurs varies from pulsar to pulsar. The rate of change of the diffractive scintillation modulation for the Vela Pulsar is relatively fast (timescale of the order of a few seconds) and the decorrelation bandwidth is narrow (a few tens of Hz). This is thought to be due to the closest of the bulk of scattering medium to the pulsar. The Vela Pulsar is unusual in this respect. Refractive Scintillation A longer term effect called refractive scintillation causes variations of the order of days to months. It is thought that this is due to wholesale focussing/defocussing of signals by the ISM. The exact type of material which causes this effect is not known.

This effect is fairly mild for Vela, but can result in a variation of up to a couple of dB day-to-day and nearly 3 dB over time scales of a couple of months and years. This means where attempts are being made to incoherently sum daily Vela data there can be expected to be runs of days where the S/N is substantially better than other periods. It is noted, however, that the Crab Pulsar has been observed to vary in strength by almost 10 dB over a year of elapsed time, with 4 dB variation day-to-day. This is in addition to the short-term variations due to diffractive scintillation which are of the order, in time, of a single observation run of a few hours. Polarisation In general most radio signals emanating from outside the solar system are randomly polarised - meaning that they can be received at equal strength with any orientation of a linearly-polarised antenna. In contrast, signals from pulsars are relatively strongly linearly polarised - meaning that at any instance there will be an orientation of a linearly polarised antenna which will return maximum signal. At that same instance an antenna orthogonal to that orientation will receive no signal.

For the receiving system it becomes a problem of making sure the alignment of a linearly polarised antenna is orientated for best pickup. If the polarisation of the incoming pulsar signal was known then this could be achieved by rotating the antenna polarisation to match. However, in practice this is not feasible as the orientation is not only affected by the ISM, but also by an additional variable Faraday rotation in the ionosphere. But the over-riding factor that makes it impractical is that the orientation of the polarisation from the pulsar itself swings significantly even during the on-phase of the pulse. For the Vela Pulsar there is more than a 90° shift in polarisation over the W10 time (4.5 ms) of the on-pulse !!! To circumvent the effects of the polarisation swing, one can use a circularly polarised antenna. This carries a 3 dB penalty compared to a linearly polarised antenna orientated for maximum pickup, but as it is impractical to implement a dynamic linear polarisation tracking system, that deficit must be accepted.

Astronomers Find Spinning Neutron Star Tied to Mysterious Tail Astronomers Find Spinning Neutron Star Tied to Mysterious Tail 07/14/11 AT 2:42 AM Close A mysterious long X-ray tail spanning more than 4 light years across may be stretching away from a spinning neutron star, or pulsar, according to astronomers who discovered the event using NASA's Chandra X-ray Observatory. The pulsar, named PSR J0357+3205, is located about 1,600 light years from Earth and was originally discovered by the Fermi Gamma Ray Space Telescope in 2009. Astronomers calculate that the pulsar is about half a million years old, which makes it roughly middle-aged for this type of object. [[nid:43990]] Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation, which can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name.

Neutron star, as its name implies composed almost entirely of neutrons, is a type of stellar remnant resulting from the gravitational collapse of a massive star during a supernova event. The image shows NASA's Chandra data in blue and Digitized Sky Survey data in yellow. The position of the pulsar at the upper right end of the tail is seen by mousing over the image. The two bright sources lying near the lower left end of the tail are both thought to be unrelated background objects located outside our galaxy. The interesting part in this discovery is the mysterious tail, which is stretching away from the pulsar. If the tail is at the same distance as the pulsar then it stretches for 4.2 light years in length, making it one of the longest X-ray tails ever associated with a so-called rotation-powered pulsar. Rotation-powered pulsar is a class of pulsar that get its power from the energy lost as the rotation of the pulsar slows down. Astronomers say that the tail is puzzling because despite sharing characteristics with other tails extending from pulsars, it differs in certain properties.

The Chandra data indicate that the X-ray tail may be produced by emission from energetic particles in a pulsar wind, with the particles produced by the pulsar spiraling around magnetic field lines. Other X-ray tails around pulsars have been interpreted as bow-shocks generated by the supersonic motion of pulsars through space, with the wind trailing behind as its particles are swept back by the pulsar's interaction with the interstellar gas. However, this bow-shock interpretation may or may not be correct for PSR J0357, with several issues that need to be explained. For instance, the Fermi data show that PSR J0357 is losing a very small amount of energy as its spin slows down with time. Astronomers noted that this energy loss is important as it is converted into radiation and powering a particle wind from the pulsar. This places limits on the amount of energy that particles in the wind can attain, and so might not account for the quantity of X-rays seen by Chandra in the tail. In addition, other pulsars with bow-shocks show bright X-ray emission surrounding the pulsar, and this is not seen for PSR J0357.

Also, the brightest portion of the tail is well away from the pulsar and this differs from what has been seen for other pulsars with bow-shocks. Astronomers hope that further observations could help test this bow-shock interpretation. If the pulsar is seen moving in the opposite direction from that of the tail, this would support the bow-shock idea. ⑨ - YouTube ⑨ Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. Rating is available when the video has been rented. This feature is not available right now. Please try again later. Uploaded on May 5, 2010 Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses is very regular.

For some pulsars, the regularity of pulsation is as precise as an atomic clock. A few pulsars are known to have planets orbiting them, such as PSR B1257+12. Werner Becker of the Max Planck Institute for Extraterrestrial Physics said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work." Category Pulsars discovered by Jocelyn Bell Burnell and Antony Hewish. in year 1967 Discovered by : Jocelyn Bell Burnell and Antony Hewish. Discovered in year : 1967 Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect as it has has a mechanism to beam light just like a Lighthouse. These effect give rise to the pulsed nature of the stars that gives pulsars their name.

Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses is very regular. Pulsars pulse because the rotation of the neutron star causes the radiation generated within the magnetic field to sweep in and out of our line of sight with a regular period. Several hundred pulsars are now known, with periods ranging from seconds down to sub-milliseconds. Two pulsars, the Crab and the Vela Pulsars, are strong sources of gamma rays. History of the Discovery The first pulsar was observed on November 28, 1967 by Jocelyn Bell Burnell and Antony Hewish. When they discovered it, they were baffled as it had unnatural regularity of emissions so they dubbed their discovery LGM-1, for "Little Green Men" (a name for intelligent beings of extraterrestrial origin). Their pulsar was later dubbed CP 1919, and is now known by a number of designators including PSR 1919+21, PSR B1919+21 and PSR J1921+2153.

Although CP 1919 emits in radio wavelengths, pulsars have, subsequently, been found to emit in visible light, X-ray, and/or gamma ray wavelengths. The word "pulsar" is a contraction of "pulsating star", and first appeared in print in 1968. Development in the Discovery of Pulsars The most famous pulsar was discovered shortly after that. It lies in the Crab Nebula (M1), which is about 7000 light years away in the constellation Taurus. The Crab Pulsar rotates about 30 times a second, emitting a double pulse in each rotation in the RF through gamma-ray spectrum. The suggestion that pulsars were rotating neutron stars was put forth independently by Thomas Gold and Franco Pacini in 1968, and was soon proven beyond reasonable doubt by the discovery of a pulsar with a very short (33-millisecond) pulse period in the Crab nebula. In 1974, Antony Hewish became the first astronomer to be awarded the Nobel Prize in physics.

Considerable controversy is associated with the fact that Professor Hewish was awarded the prize while Bell, who made the initial discovery while she was his Ph.D student, was not. In the same year i.e.1974, Joseph Hooton Taylor, Jr. and Russell Hulse discovered the first time pulsar in a binary system, PSR B1913+16. This pulsar orbits another neutron star with an orbital period of just eight hours. In 1993, the Nobel Prize in Physics was awarded to Taylor and Hulse for the discovery of this pulsar. In 1982, Don Backer led a group which discovered PSR B1937+21, a pulsar with a rotation period of just 1.6 milliseconds. Observations soon revealed that its magnetic field was much weaker than ordinary pulsars, while further discoveries cemented the idea that a new class of object, the "millisecond pulsars" (MSPs) had been found. MSPs are believed to be the end product of X-ray binaries.

In 1992, Aleksander Wolszczan discovered the first extrasolar planets around PSR B1257+12. This discovery presented important evidence concerning the widespread existence of planets outside the solar system, although it is very unlikely that any life form could survive in the environment of intense radiation near a pulsar. In June 2006, the astronomer John Middleditch and his team at LANL announced the first prediction of pulsar glitches with observational data from the Rossi X-ray Timing Explorer. They used observations of the pulsar PSR J0537-6910. Role of the Discovery of Pulsars in the improvement of Human Life The study of pulsars has resulted in many applications in physics and astronomy. Striking examples include the confirmation of the existence of gravitational radiation as predicted by general relativity and the first detection of an extrasolar planetary system. MSPs can be used by astronomers as clocks rivalling the stability of the best atomic clocks on Earth. Factors affecting the arrival time of pulses at the Earth by more than a few hundred nanoseconds can be easily detected and used to make precise measurements.

The discovery of pulsars has allowed astronomers to study an object never observed before, the neutron star. Neutron Star is the only place where the behaviour of matter at nuclear density can be observed (though not directly). Also, millisecond pulsars have allowed a test of general relativity in conditions of an intense gravitational field. Pulsar maps have been included on the two Pioneer Plaques as well as the Voyager Golden Record. They show the position of the Sun, relative to 14 pulsars, which are identified by the unique timing of their electromagnetic pulses, so that our position both in space and in time can be calculated by potential extraterrestrial intelligences. Other Discoveries Pulsar - definition and synonims of «pulsar» in english dictionary pulsar Meaning of pulsar in the english dictionary online DICTIONARY ETYMOLOGY OF THE WORD PULSAR From puls( ating st) ar, on the model of quasar. Etymology is the study of the origin of words and their changes in structure and significance. PRONUNCIATION OF PULSAR exclamation Pulsar is a noun. A noun is a type of word the meaning of which determines reality.

Nouns provide the names for all things: people, objects, sensations, feelings, etc. DEFINITION OF PULSAR Pulsar A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can only be observed when the beam of emission is pointing toward the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range from roughly milliseconds to seconds for an individual pulsar. The precise periods of pulsars makes them useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12. Certain types of pulsars rival atomic clocks in their accuracy in keeping time.

Synonyms and antonyms of pulsar in the english dictionary of synonyms SYNONYMS WORDS RELATING TO «PULSAR» pulsar vaporizer food watches game night vision vela bajaj highly magnetized rotating neutron star that emits beam electromagnetic radiation this only landing page welcome pulsar please select your region asia europe oceania south africa north america global website canada home what campaign live style lucky magazine candy maxim more getting younger inspired extreme sports young sportsmen women enjoy imagine universe nasa beams sweep through sight like black hole endpoint stellar evolution lighting control desks dimmers strobe emitting diode today formation similar creation massive with times mass dies rogue amoeba longer being developed recent moves siriusxm forced retire effective october available purchase while still process measurement level flow northumbrian water installed quantum pumping station controller which features ability link four pulse about Online english translator with the translation of pulsar into 20 languages TRANSLATOR TRANSLATION OF PULSAR Find out the translation of pulsar to 20 languages with english dictionary multilingual translator. The translations of pulsar to other languages presented in this section have been obtained through automatic statistical translation; where the essential translation unit is the word «pulsar» in English.

List of principal searches undertaken by users to access our online dictionary and most widely used expressions with the word «pulsar». FREQUENCY OF USE OF THE TERM «PULSAR» OVER TIME The graph expresses the annual evolution of the frequency of use of the word «pulsar» during the past 500 years. Its implementation is based on analysing how often the term «pulsar» appears in digitalised printed sources in English between the year 1500 and the present day. Examples of use in the literature, quotes and news about pulsar EXAMPLES 10 BOOKS RELATING TO «PULSAR» Discover the use of pulsar in the following bibliographical selection. Books relating to pulsar and brief extracts from same to provide context of its use in literature. 1 Handbook of Pulsar Astronomy This work will be of great value not only to graduate students but also to researchers wishing to carry out and interpret a wide variety of radio pulsar observations. D. R. Lorimer, M.

Kramer, 2005 2 Pulsar Astronomy the pulsar were so strong that they immediately showed their periodicity of 89 ms on the pen chart recordings (Large, Vaughan & Mills 1968). This was the shortest pulsar period then known. The discoverers noted that the pulsar is located near ... Andrew Lyne, Francis Graham-Smith, 2012 3 Physics of the Pulsar Magnetosphere This book presents the theory of the electrodynamic phenomena that occur in the magnetosphere of a pulsar. A. V. Gurevich, V. S. Beskin, Jakov N. Istomin, 2006 4 Pulsar: for solo violin For solo violin. Commissioned by the Royal Philharmonic Society and the BBC3 as part of New Generation Artist Works. Premiered by Ilya Gringolts on March 17, 2003 in London's Wigmore Hall. Augusta Read Thomas, 2005 8 Pulsar astronomy, 2000 and beyond: IAU Colloquium, 177 : ... Contributors include astronomers and physicists from around the world.

Annotation c. Book News, Inc., Portland, OR (booknews.com) Michael Kramer, N. Wex, R. Wielebinski, 2000 9 Horizons: Exploring the Universe X-ray image Pulsar PSR0540–69 located in a 1000-year- old supernova remnant Ring and jets produced by pulsar wind Pulsar wind nebula Rings and jets produced by pulsar wind 3000-year-old supernova remnant G54.1+0.3 □ Figure 11-4 ... Michael Seeds, Dana Backman, 2009 10 Observations of High Energy Emission from Pulsar Wind ... VERITAS (the Very Energetic Radiation Imaging Telescope Array System) recently observed several of these sources in an attempt to detect very high energy gamma rays created in their nebulae. John P. Millis, 2008 10 NEWS ITEMS WHICH INCLUDE THE TERM «PULSAR» Find out what the national and international press are talking about and how the term pulsar is used in the context of the following news items.

1 Bajaj stretches the Pulsar effect With eight models under its name, Pulsar is Bajaj's most hard working brand. Besides three launches in quick succession this calender year, Pulsar's sales ... «Business Standard, Jul 15» 2 This Pulsar Is Shotgunning Part Of Its Neighbor Out Into Space Pulsars are kind of like the action stars (pun very much intended) of the universe, bringing crazy force and wild maneuvers to their galaxies and even sometimes ... «Forbes, Jul 15» 3 Stellar fireworks predicted during rare pulsar encounter in 2018 The pulsar, known as J2032+4127 (J2032 for short), is the crushed core of a massive star that exploded as a supernova. It is a magnetised ball about 12 miles ... «Astronomy Now Online, Jul 15» 4 High school researchers discover pulsar with widest orbit ever … Artist's impression of pulsar PSR J1930-1852 shown in orbit around a companion neutron star. Discovered by a team of high school students, this pulsar has the ...

«Astronomy Now Online, May 15» 5 Overwhelming Response For Bajaj Pulsar RS200; 3500 Bookings in … Launched on 26th March, 2015, the Bajaj Pulsar RS200 has received over 3,500 bookings, says Bajaj Auto. The vehicle was launched in two versions ... «NDTVAuto.com, Apr 15» 6 New Bajaj Pulsars: What's the Difference? Sports bikes - what would we have ever done without them? While Bajaj conjured the Pulsar RS200, Kawasaki took things further with the Ninja H2, and since ... «NDTVAuto.com, Apr 15» 7 Bajaj Pulsar RS200 Review: First Ride Report Before I start off with my impression of the Bajaj Pulsar RS200 after the brief ride I had on it at Bajaj's test track in Chakan, I must accept that I suffer from a little ...

«NDTVAuto.com, Apr 15» 8 Bajaj Pulsar RS200 Launched; Prices Start at Rs. 1.18 Lakhs After a long wait, Bajaj has finally launched the RS200. This is the fastest Pulsar from the Bajaj stable. The bike will be available in two versions Non ABS and ... «NDTVAuto.com, Mar 15» 9 Bajaj Pulsar RS200: What we know right now The new Bajaj Pulsar RS 200 will be launched in India on March 26, 2015. A highly awaited motorcycle, it is expected to set new performance benchmarks in the ... «Overdrive, Mar 15» 10 Warped space-time tips pulsar out of view A pulsar, one of deep space's spinning “lighthouses”, has faded from view because a warp in space-time tilted its beams away from Earth. The tiny, heavy pulsar ... «BBC News, Jan 15» REFERENCE Pulsars "blink" because they _____.

are rotating release bursts of photons every few microseconds release burst of gamma rays when their surface is cracked have a strong magnetic field You have new items in your feed. Click to view. Question and answer Pulsars "blink" because they _____. are rotating release bursts of photons every few microseconds release burst of gamma rays when their surface is cracked have a strong magnetic field A. are rotating. A pulsar (portmanteau of pulsating star) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. [ This radiation can only be observed when the beam of emission is pointing towards the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval, between pulses that range from roughly milliseconds to seconds for an individual pulsar. ] Expert answered| icebelmonte |Points 140| All About Heaven - Some science behind the scenes Some science behind the scenes Pulsars Pulsars are highly magnetized rotating neutron stars which emit a beam of detectable electromagnetic radiation in the form of radio waves.

Their observed periods range from 1.4 ms to 8.5 s. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. For some pulsars, the regularity of pulsation is as precise as an atomic clock. Pulsars are known to have planets orbiting them, as in the case of PSR B1257+12. Werner Becker of the Max-Planck-Institut für extraterrestrische Physik said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work." Three distinct classes of pulsars are currently known to astronomers, according to the source of energy that powers the radiation: Rotation-powered pulsars, A Rotation-powered pulsar is a rapidly rotating neutron star, whose electromagnetic radiation is observed in regularly spaced intervals, or pulses. It differs from other types of pulsars in that the source of power for the production of radiation is the loss of rotational energy.

Accretion-powered pulsars (accounting for most but not all X-ray pulsars), where the gravitational potential energy of accreted matter is the energy source (producing X-rays that are observable from Earth). The X-ray periods range from as little as a fraction of a second to as much as several minutes. An X-ray pulsar consists of a magnetized neutron star in orbit with a normal stellar companion and are a type of binary star system. The magnetic field strength at the surface of the neutron star is typically about 1012 gauss, over a trillion times stronger than the strength of the magnetic field measured at the surface of the Earth (0.6 gauss). Magnetars, where the decay of an extremely strong magnetic field powers the radiation. Although all three classes of objects are neutron stars, their observable behaviour and the underlying physics are quite different. There are, however, connections. For example, X-ray pulsars are probably old rotation-powered pulsars that have already lost most of their energy, and have only become visible again after their binary companions expanded and began transferring matter on to the neutron star.

The process of accretion can in turn transfer enough angular momentum to the neutron star to "recycle" it as a rotation-powered millisecond pulsar. At the centre of the Crab nebula lies the Crab Pulsar, a rotating neuron star, which emits pulses of radiation from gamma rays to radio waves with a spin rate of 30.2 times per second. The Crab Pulsar is believed to be about 28–30 km in diameter; it emits pulses of radiation every 33 milliseconds. Pulses are emitted at wavelengths across the electromagnetic spectrum, from radio waves to X-rays. Observations For iPad/iPhone users: tap letter twice to get list of items. © Copyright 2004-2017 - All About Heaven.org | Disclaimer | Designed and made by: Strut Your Stuff

Question: What is a highly magnetized, rotating, neutron star emitting a beam of electromagnetic radiation that can only be observed when the beam of emission is pointing towards the Earth (known as the lighthouse effect)?
Answer: Pulsar