Diagram explaining pulsar mechanics courtesy of nasa.gov
Another example showing the strong magnetic field and emission beams courtesy of ulsar_schematic.svg" target="_blank" class="postlink">wikipedia.org
Text and X-ray image showing a pulsar in the Crab Nebula “on” and when it is “off” (EM beams away from Earth) courtesy of nasa.gov
Image showing geometry and mechanics of pulsars courtesy of nasa.gov
Some notable pulsars…
The first radio pulsar CP 1919 (now known as PSR 1919+21), with a pulse period of 1.337 seconds and a pulse width of 0.04 second, was discovered in 1967. A drawing of this pulsar's radio waves was used as the cover of British rock band Joy Division's debut album, "Unknown Pleasures".
• The first binary pulsar, PSR 1913+16, whose orbit is decaying at the exact rate predicted due to the emission of gravitational radiation by general relativity
• The first millisecond pulsar, PSR B1937+21
• The brightest millisecond pulsar, PSR J0437-4715
• The first X-ray pulsar, Cen X-3
• The first accreting millisecond X-ray pulsar, SAX J1808.4-3658
• The first pulsar with planets, PSR B1257+12
• The first double pulsar binary system, PSR J0737−3039
• The longest period pulsar, PSR J2144-3933
• The most stable pulsar in period, PSR J0437-4715
• The magnetar SGR 1806-20 produced the largest burst of energy in the Galaxy ever experimentally recorded on 27 December 2004
• PSR B1931+24 "... appears as a normal pulsar for about a week and then 'switches off' for about one month before emitting pulses again. [..] this pulsar slows down more rapidly when the pulsar is on than when it is off. [.. the] braking mechanism must be related to the radio emission and the processes creating it and the additional slow-down can be explained by a wind of particles leaving the pulsar's magnetosphere and carrying away rotational energy.
• PSR J1748-2446ad, at 716 Hz, the pulsar with the highest rotation speed.
• PSR J0108-1431, the closest known pulsar to the Earth. It lies in the direction of the constellation Cetus, at a distance of about 85 parsecs (280 light years). Nevertheless, it was not discovered until 1993 due to its extremely low luminosity. It was discovered by the Danish astronomer Thomas Tauris. in collaboration with a team of Australian and European astronomers using the Parkes 64-meter radio telescope. The pulsar is 1000 times weaker than an average radio pulsar and thus this pulsar may represent the tip of an iceberg of a population of more than half a million such dim pulsars crowding our Milky Way.
• PSR J1903+0327, a ~2.15 ms pulsar discovered to be in a highly eccentric binary star system with a sun-like star.
• A pulsar in the CTA 1 supernova remnant initially emitted radiation in the X-ray bands. Strangely, when it was observed at a later time X-ray radiation was not detected. Instead, the Fermi Gamma-ray Space Telescope detected the pulsar was emitting gamma ray radiation, the first of its kind.
Image of optical/X-ray composite of pulsar in Crab Nebula, notice the emission beam seen and the swirling look of the nebula cloud caused by ‘pulsar wind’. The pulsar wind is caused by the high speed of the particles shooting from the pulsar as well the strong magnetic field. Courtesy of wikipedia.org.
Image of Vela Pulsar in the middle of its surrounding pulsar wind nebula courtesy of wikipedia.org
Image of artists depiction of a magnetar courtesy of universetoday.com
Magnetars are yet another manifestation a neutron star can take. Magnetars have an extremely powerful magnetic field, hence the name, when it decays it releases powerful amounts of X-rays and gamma rays. A magnetar does not pulse ‘beacons’ of radio or light energy from its poles like a pulsar. Like neutron stars and pulsars, a magnetar is no bigger than 12 miles in diameter but extremely dense with mass. They rotate very slowly compared to pulsars, although some do not as we will see later on. The closest discovered magnetar to Earth is 13,000 lightyears distant.Magnatars have a relatively short life of around 10,000 years, after which they become ‘inactive’ and essentially revert back to a neutron star. The magnetic fields of magnetars can often reach ten gigateslas in strength, for comparison the Earth has a field strength of 30-60 microteslas. It is thought that the field is so strong it would kill humans within 1000 kilometers of it. Also it is thought that a magnetar could wipe all magnetic credit card bands clean from a distance of halfway to the Moon, or about 100,000 miles. It is thought that one out of ten supernovae result in a magnetar forming, as opposed to the more common neutron star or pulsar. As of May 2007 only twelve magnetars have been confirmed, with more awaiting confirmation. Magnetars are also thought responsible for GRB’s (gamma ray bursts) and soft gamma repeaters. The magnetars magnetic field is so strong it twists its own crust which produces currents that form electron clouds around the star, which interact with the radiation coming from the stellar surface to form X-rays and gamma rays. Stellarquakes, sometimes called “Magnetar Quakes” or “Pulsar Quakes” occur in both a magnetar and a pulsar. They are thought to be caused by huge stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior magnetic fields. Sometimes the quakes can be so bad that they cause the very powerful GRBs. Sometimes magnetars and pulsars under go what is called a glitch, which is the sudden speeding up of the stars rotational period and a large increase in energy. It can last from days to years. It is thought that this is another cause of starquakes, particularly in pulsars. In 2004 a quake on a pulsar 50,000 lightyears away arrived in our solar system, temporarily knocking out every X-ray satellite in space. Had this event happened within ten lightyears from Earth it would have caused a mass extinction similar to the Permian Extinction. This should show you how much energy is expended by these stars. Luckily now astronomers and astrophysicist can now predict these quakes:
Scientists have discovered how to predict earthquake-like events in pulsars. These explosive episodes likely crack a pulsar's dense crust and momentarily bump up its spin rate.
Using NASA's Rossi X-ray Timing Explorer, the team has tracked about 20 "starquakes" on one particular pulsar over the past eight years and uncovered a remarkably simple, predictive pattern.
[edit on 6/20/2009 by jkrog08]
[edit on 6/20/2009 by jkrog08]