In 2003, astronomers discovered that the orbits of neutron stars intersect each other and emit radiation light
A double pulsar is a neutron star whose orbits intersect each other and emit radiation light, which was discovered by astronomers in 2003.Both neutron stars are pulsars.An in-depth study of this group of rotating objects will provide the most rigorous experiment for Einstein's gravitational wave theory.At the end of 2003, the discovery was rated as one of the top ten scientific breakthroughs by Science magazine. Astronomers hope to know the density of matter inside a neutron star by studying the radiation light.
Chinese name
Double pulsar
Features
The tracks intersect each other and radiate light.
sincehuman beingsAfter the evolution to two feet on the ground and blue sky overhead, the mysterious starry sky has fascinated countless people, and its charm is endless, attracting generations of people who have been unremittingly exploring.So far, human beings have learned a lot about it.
Since the discovery of the first radio pulsar binary, PSR1913+16, by professors Huls and Taylor in 1974, astronomers have spent 30 years to discover this binary pulsar system, which is so difficult and precious.
PSRJ0737-3039A, which was discovered in April 2003, has a period of 22 milliseconds. Its pulse period is changing, sometimes long and sometimes short, and there are rules to find. Based on this, scientists confirmed that this is a binary system, and published this result in the December 2003 issue of Nature.
In 2004, when the data from Australia's Parkes astronomical telescope were re analyzed, researchers confirmed that Star B was actually a pulsar.
In 2004, astronomers made another breakthrough. Astronomers found that a pair of high-speed rotatingPulsarThe binary star is called PSRJ0737-3039A/B, which is called one of the neutron stars studied by human beings in the past 36 years“watershed”The discovery of formula.
Compared with the PSR1913+16 discovered in 1974Pulsar binaryIn contrast, this double pulsar system has a shorter orbital period and stronger gravitational radiation, making it a more ideal gravitational wave laboratory.The two stars in the binary system are both pulsars, which also become the laboratory for studying the interaction between two pulsars.This means that the double pulsar system discovered this time has new characteristics and higher research value.
Research difficulty
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Young neutron stars areStrong magnetostar, with strongDipole magnetic field。High energy electrons will be continuously generated in the magnetic pole crown area. High energy electrons can only move outward along the open magnetic line of force and generate radiation in the extremely strong magnetic field.Therefore, two magnetic pole crowns are formedconicLike a lighthouse on the sea, two powerful radio waves are emitted from the radiation area of.Its rotation makes these two radiation cones rotate around the rotation axis. Every time the radiation beam of the neutron star sweeps the earth, ourradio telescopeA very narrow pulse signal is received.This is why neutron stars are called pulsars.
The double pulsar system can only be found when the radiation beams of both pulsars can sweep the earth.However, the radiation beam of the pulsar is very narrow, and there is little chance that the radiation beam of both stars can sweep the earth.So it is very difficult to find double pulsar system.
This discovery was made through the cooperation of several countriesAustraliaParkes' 64 meter caliberradio telescope, every dayuniverseSearch in.
Galactic characteristics
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From the perspective of evolution, the probability of producing binary stars, that is, double neutron star systems, is relatively small, and double pulsar systems are even less.To form a double neutron star system, the mass of both stars is required to be relatively large.And the second star evolved toSupernovaDuring the explosion, the second neutron star is often produced and the binary star system is disintegrated at the same time. Only a few of them can form dual neutron star systems.The double pulsar system discovered this time is not only not disintegrated, but also composed of a millisecond pulsar (Star A - period 22 milliseconds) and a normal pulsar (Star B - period 2.27 seconds). Star A is old, rotating fast, and has a weak magnetic field;Star B is young, with slow rotation speed and strong magnetic field.Coincidentally withMillisecond pulsarThe resulting theoretical model fits. "
research subject
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In addition to further verifying Einstein's gravitational wave theory, this discovery also has a very new research topic.
The first problem is the interaction between two pulsars.It is observed that in the 2.4 hours of an orbital period, star B can only be observed in a short period of two 10 minutes. Scientists suspect that this is because the "star wind" emitted by star A has an impact on star B. But why is it so influential?How did it affect?Not clear yet.
The second question is that the radiation of both pulsars may pass through the magnetosphere of their companion pulsars. In particular, the magnetosphere of star B is 100 times larger than that of star A, which is easier to detect. What will be the detection result?Very attractive.
The third point is that the orbital precession of A and B is very large, which are 75 degrees and 71 degrees each year respectively.The precession of the orbit will lead to changes in the shape of the pulse profiles we observe, which will be another very attractive observation topic. Will the pulse profiles of these two pulsars change?How?We will look forward to it.
After the discovery of the double pulsar PSRJ0737-3039A/B, people are really looking forward to the change of the pulse contour shape of the two pulsars, and even predict that it will be around 2020,PSRJ0737-3039A will disappear from our sight due to the axis precession. However, the observation results in recent years show that the expected pulse contour shape has not changed at all, which is a big blow to scientists.The failure of the prediction made us feel that there seems to be a problem with the pulsar beacon model.
Research progress
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New Stars' Ten Year Magpie Bridge "Meeting"
It is understood that the neutron star merger event will produce very strong gravitational waves, which may be found by the most sensitive gravitational wave detector on earth.Physicists expect to receive gravitational waves from the merging event of two neutron stars in space one day.The orbital period of the newly discovered double pulsar system is more than three times shorter than that of PSR1913+16, and the merging will take place about 85 million years later.[1]
According to the case of PSR1913+16 discovered in 1974, it would take 100 years for a double neutron star merging event to occur, and according to the case of the newly discovered double pulsar system, it would take about 10 years for a merging event to occur.Scientists are waiting for the neutron star merging event to happen, and there is more hope.
The orbit period of this pair of stars is only 2.4 hours, the orbit is relatively round, the ellipticity is 0.088, the average speed reaches 0.1% light speed, the mass of star A is 1.337 solar mass, and the mass of companion star is 1.251 solar mass.The two pulsars are closer to each other than PSR1913+16, only 900000 kilometers[1]The gravitational radiation is stronger, and obvious orbital changes can be observed in one year.
Research on double pulsars and gravitational wave detection
On Earth, physicists have designed many special instruments in the hope of receiving gravitational waves from space.More than half a century has passed without success.
The discovery of radio pulsar binaries in 1974 brought hope for the detection of gravitational waves.U.S.AThe binary star discovered by Professor Huls and Taylor of the University of California is composed of two neutron stars. Its orbital period is very short, only 7.75 hours.The orbit is elliptical, and the ellipticity is large, reaching 0.617.This results in its orbital speed reaching one tenth of the speed of light at its highest.The two neutron stars are very close and have strong gravitational radiation.Gravitational radiation can cause two neutron stars to get closer and closer, and the orbital period is shorter and shorter.General relativity theory has accurately calculated the rate of change of orbital period.To detect the existence of gravitational waves, the most important thing is to accurately measure the orbital period of radio pulse binaries through observation.Taylor and others used the world's largestradio telescopeThousands of observations have been made, providing evidence for human beings to confirm the existence of gravitational waves.
The observation of the newly discovered double pulsar system will provide Einstein's general relativity and gravitational wave theory with the strictest test so far: if the theory of relativity is followed, their high density will lead to space bending.When both of them are in a straight line with the earth, if B is far away and A is near, the pulse signal of B will pass by A if it wants to reach the earth.However, A's strong gravity will bend the surrounding space, so B needs to go through this curve to reach the Earth.This situation has been observed by scientists, and the extra distance makes the signal 100 microseconds late.This shows that space does become curved there.[1]
Formation of neutron stars
After the aging of a massive star, the outward radiation pressure of the star cannot compete with the inward gravity, and its shell will expand outward while its core will shrink inward.A series of complex physical changes take place in the nucleus under huge pressure and the resulting high temperature. Electrons are compressed into the nucleus, neutralized with protons as neutrons, making the atom only composed of neutrons.At this time, the shell of a star will end its life with a spectacular explosion, which is also known as "supernova explosion" in astronomy.Finally, the remaining nucleus becomes a neutron star.It is this process of evolution that makes neutron stars known as "death stars".
Formation of gravitational waves
Einstein predicted in his general theory of relativity in 1916 that there might be gravitational waves in space.That is, any object with mass will generate gravitational waves when accelerating.Gravitational waves can affect objects with mass.
