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PSR J0737−3039 is the first known double
pulsar A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...
. It consists of two
neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
s emitting
electromagnetic waves In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ran ...
in the radio wavelength in a relativistic
binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...
. The two pulsars are known as PSR J0737−3039A and PSR J0737−3039B. It was discovered in 2003 at
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
's
Parkes Observatory Parkes Observatory is a radio astronomy observatory, located north of the town of Parkes, New South Wales, Australia. It hosts Murriyang, the 64 m CSIRO Parkes Radio Telescope also known as "The Dish", along with two smaller radio telescopes. T ...
by an international team led by the Italian radio astronomer Marta Burgay during a high-latitude pulsar survey.


Pulsars

A pulsar is a
neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
which produces pulsating radio emission due to a strong
magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
. A neutron star is the ultra-compact remnant of a massive star which exploded as a
supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
. Neutron stars have a mass bigger than the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, yet are only a few kilometers across. These extremely dense objects rotate on their
axes Axes, plural of ''axe'' and of ''axis'', may refer to * ''Axes'' (album), a 2005 rock album by the British band Electrelane * a possibly still empty plot (graphics) See also * Axis (disambiguation) An axis (: axes) may refer to: Mathematics ...
, producing focused
electromagnetic waves In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ran ...
which sweep around the sky and briefly point toward Earth in a lighthouse effect at rates that can reach a few hundred pulses per second. Although double neutron star systems were known before its discovery, PSR J0737−3039 is the first and only known system () where both neutron stars are pulsars – hence, a "double pulsar" system. The object is similar to PSR B1913+16, which was discovered in 1974 by Jocelyn Bell,
Taylor Taylor, Taylors or Taylor's may refer to: People * Taylor (surname) ** List of people with surname Taylor * Taylor (given name), including Tayla and Taylah * Taylor sept, a branch of Scottish clan Cameron * Justice Taylor (disambiguation) ...
and Hulse, and for which the two won the 1993
Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
. Objects of this kind enable precise testing of
Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
's theory of
general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...
, because the precise and consistent timing of the pulsar pulses allows relativistic effects to be seen when they would otherwise be too small. While many known pulsars have a binary companion, and many of those are believed to be neutron stars, J0737−3039 is the first case where both components are known to be not just neutron stars but pulsars.


Discovery

PSR J0737−3039A was discovered in 2003, along with its partner, at Australia's 64 m antenna of the Parkes Radio Observatory; 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. Initially, this
star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...
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.


Physical characteristics

The orbital period of J0737−3039 (2.4 hours) is one of the shortest known for such an object (one-third that of the Taylor–Hulse binary), 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 wave Gravitational waves are oscillations of the gravitational field that Wave propagation, travel through space at the speed of light; they are generated by the relative motion of gravity, gravitating masses. They were proposed by Oliver Heaviside i ...
s appear to match the theory. As a result of energy loss due to gravitational waves, the common orbit (roughly in diameter) shrinks by 7 mm per day. The two components will coalesce in about 85 million years. : Due to relativistic spin precession, the pulses from Pulsar B are no longer detectable but are expected to reappear in 2035 due to precession back into view.


Use as a test of general relativity

Observations of 16 years of timing data have been reported in 2021 to be on agreement with general relativity by studying the loss of orbital energy due to
gravitational waves Gravitational waves are oscillations of the gravitational field that travel through space at the speed of light; they are generated by the relative motion of gravitating masses. They were proposed by Oliver Heaviside in 1893 and then later by H ...
. The
orbital decay Orbital decay is a gradual decrease of the distance between two orbiting bodies at their closest approach (the periapsis) over many orbital periods. These orbiting bodies can be a planet and its satellite, a star and any object orbiting it, or ...
and the speedup of the
orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
was tested to follow the quadrupole formula with a great precision of 0.013% mainly because of the unique characteristics of the system which has two pulsars, is nearby and possesses an inclination close to 90°.


Unique origin

In addition to the importance of this system to tests of general relativity,
Piran Piran (; ) is a town in southwestern Slovenia on the Gulf of Piran on the Adriatic Sea. It is one of the three major towns of Slovenian Istria. A bilingual city, with population speaking both Slovene and Italian, Piran is known for its medieva ...
and Shaviv have shown that the young pulsar in this system must have been born with no mass ejection, implying a new process of
neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
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.


Eclipses

Another 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 A doughnut or donut () is a type of pastry made from leavened fried dough. It is popular in many countries and is prepared in various forms as a sweet snack that can be homemade or purchased in bakeries, supermarkets, food stalls, and fran ...
shaped
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
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 In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
; some of the stronger pulsar's light can still be detected during the eclipse.


Other binary systems

In addition to a double pulsar system, a whole range of differing two-body systems are known where only one member of the system is a pulsar. Known examples are variations on a
binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
: :A pulsar–
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
system; e.g, PSR B1620−26. :A pulsar–
neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
system, e.g, 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. Theoretically, a pulsar-black hole system is possible and would be of enormous scientific interest but no such system has yet been identified. A pulsar has recently been detected 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. Also of great scientific interest is PSR J0337+1715, a pulsar-white dwarf binary system that has a third white dwarf star in a more distant orbit circling around both of the other two. This unique arrangement is being used to explore the strong equivalence principle of physics, a fundamental assumption upon which all of
general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...
rests. The
Square Kilometre Array The Square Kilometre Array (SKA) is an intergovernmental organisation, intergovernmental international radio telescope project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square ...
, a
radio telescope A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...
due to be completed in the late 2020s, will both further observe known and detect new binary pulsar systems in order to test
general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...
.


See also

*
Radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object, celestial objects using radio waves. It started in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observat ...


References


External links

* * * * * * * * * {{DEFAULTSORT:PSR J0737-3039 Puppis Pulsars Double neutron star systems