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PSR J0737−3039

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PSR J0737−3039

Artist's impression. The objects are not shown to scale: if they were depicted as the size of marbles, they would be 225 m (750 ft) apart. See also MPEG animation (2.4 MB)
Observation data
Epoch J2000      Equinox J2000
Constellation Puppis
Right ascension 07h 37m 51.247s
Declination −30° 39′ 40.74″
Characteristics
Spectral type Pulsar
Variable type None
Astrometry
Distance 3200–4500 Ly (1150 parsecs)
Details
Mass1.338 M☉
Rotation22.699379737159 ms[1][2]
PSR J0737−3039B
Details
Mass1.249 M☉
Rotation2.7734613466 s[1][2]
Other designations
PSR J0737−3039A, PSR J0737−3039, [CGB2005] J073751.248−303940.83.

PSR J0737−3039 is the only known double pulsar. It consists of two neutron stars emitting electromagnetic waves in the radio wavelength in a relativistic binary system. The two pulsars are known as PSR J0737−3039A and PSR J0737−3039B. It was discovered in 2003 at Australia's Parkes Observatory by an international team led by the radio astronomer Marta Burgay during a high-latitude pulsar survey.[3]

Pulsars

A pulsar is a neutron star which produces pulsating radio emission due to a strong magnetic field. A neutron star is the ultra-compact remnant of a massive star which exploded as a supernova. Neutron stars have a mass more than our sun, yet are only a few kilometers across. These extremely dense objects rotate on their axes, producing focused electromagnetic waves which sweep around the sky in a lighthouse effect at rates that can reach a few hundred pulses per second.

PSR J0737−3039 is the only known system containing two pulsars – thus a 'double pulsar' system. The object is similar to PSR B1913+16, which was discovered in 1974 by Taylor and Hulse, and for which the two won the 1993 Nobel Prize in Physics. Objects of this kind enable precise testing of Einstein's theory of general relativity, because the precise and consistent timing of the pulsar pulses allows relativistic effects to be seen when they would otherwise be too small. Most such binary systems are thought to consist of one pulsar and one neutron star; J0737−3039 is the first case where both components are known to be not just neutron stars but pulsars.

Physical characteristics

The orbital period of J0737−3039 (2.4 hours) is the shortest yet known for such an object (one-third that of the Taylor-Hulse object), which enables the most precise tests yet. In 2005, it was announced that measurements had shown an excellent agreement between general relativity theory and observation. In particular, the predictions for energy loss due to gravitational waves appear to match the theory.

As a result of energy loss due to gravitational waves, the common orbit shrinks by 7 mm per day. The two components will coalesce in about 85 million years.

Property Pulsar A Pulsar B
Spin period 22.699 milliseconds 2.773 seconds
Mass 1.337 solar masses 1.250 solar masses
Orbital period 2.454 hours (8834.53499 seconds)

The pulses from Pulsar B are only detectable for about 20 minutes in each 2.4-hour orbit, since plasma in the magnetosphere of Pulsar A eclipses them over the rest of the orbit.

Discovery

PSR J0737−3039A was discovered in 2003, along with its partner at Australia's 65m Parkes Radio Observatory, however J0737−3039B was not identified as a pulsar until a second observation. The system was originally observed by an international team during a high-latitude multibeam survey organized in order to discover more pulsars in the night sky.[1] Initially this system was thought to be an ordinary pulsar detection. The first detection showed one pulsar with a period of 23 milliseconds in orbit around a neutron star. Only after follow up observations was a weaker second pulsar detected with a pulse of 2.8 seconds from the companion star.

Although over 1400 pulsars have been detected since their discovery in 1967 by Anthony Hewish and Jocelyn Bell at Cambridge University, this particular system has caused a lot of excitement. Previous observations have recorded a pulsar orbiting a neutron star, but never two pulsars orbiting each other.[4]

Implications

The double pulsar system PSR J0737−3039 is being studied in order to test Einstein's general theory of relativity put forward in 1915. The investigation of double pulsars is a great opportunity as the environment created by warped space-time due to the shift of intense masses is extremely rare, and thus perfect for the testing of Einstein's theory and the observation of gravitational waves.[5]

Unique origin

In addition to the importance of this system to tests of general relativity, Piran and Shaviv[6] have shown that the young pulsar in this system must have been born with no mass ejection, implying a new process of neutron star formation that does not involve a supernova. Whereas the standard supernova model predicts that the system will have a proper motion of more than hundred km/s, they predicted that this system would not show any significant proper motion. Their prediction was later confirmed by pulsar timing.[7]

Eclipses

Another great discovery from the double pulsar is the observation of an eclipse from a conjunction of the superior and weaker pulsar. This happens when the doughnut shaped magnetosphere of one pulsar, which is filled with absorbing plasma, blocks the companion pulsar's light. The blockage, lasting more than 30 s, is not complete, due to the orientation of the plane of rotation of the binary system relative to Earth and the limited size of the weaker pulsar's magnetosphere; some of the stronger pulsar's light can still be detected during the eclipse.

Other binary systems

A whole range of differing two-body systems can occur, where a pulsar exists. Other than a double pulsar system, these systems also occur:

A pulsar-white dwarf system; Such as the PSR B1620-26 binary star.
A pulsar-neutron star system, such as PSR B1913+16.
A pulsar and a normal star; e.g, PSR J0045−7319, a system that is composed of a pulsar and main-sequence B star.

A pulsar has recently been detected[8] very near the super-massive black hole at the core of our galaxy, but its motion has not yet been officially confirmed as a capture orbit of Sgr A*. A pulsar-black hole system could be an even stronger test of Einstein's theory of General Relativity, due to the immense gravitational forces exerted by both celestial objects. The Square Kilometre Array, a planned Radio Telescope due to be constructed in the southern hemisphere in 2018 (first light in 2020), will observe binary pulsar systems. It will also search for pulsar-black hole systems in order to test General Relativity.[9]

References

  1. ^ a b c The first double pulsar - List of the team. Retrieved 2010-07-07
  2. ^ a b ATNF Pulsar Catalogue database [1].
  3. ^ "An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system"- Retrieved 2010-07-07
  4. ^ "The Double Pulsar" Retrieved 2010-07-07
  5. ^ J. H. Taylor, Philos. Trans. R. Soc. London Ser. A 341, 117 (1992). "Pulsar Timing and Relativistic Gravity"
  6. ^ T. Piran & N. Shaviv Origin of the Binary Pulsar J0737−3039B, PRL, 95, 1102, 2005 "[2]".
  7. ^ M. Kramer, et al., Annalen der Physik 15, 34 (2006) "[3]".
  8. ^ A magnetar / SGR / radio pulsar only 3” from Sgr A* "[4]".
  9. ^ "Strong field tests of gravity using pulsars and black holes" Retrieved 2010-07-06.

Pulsar video: http://www.physics.mcgill.ca/~bretonr/doublepulsar/doublepulsar_artistic_small.mov

Sound clip http://www.physics.mcgill.ca/~bretonr/doublepulsar/doublepulsar_sound.mp3

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