What is an astronomical clock?

Astronomers have discovered that a rapidly rotating pulsar in the constellation of Sailboat, if the rate of its rotation is used as a timepiece, it will be inaccurate by only one second every three million years, which is 10 times more accurate than the current "atomic clock". Therefore, astronomers call it an "astronomical clock".

The pulsar is one of the four great discoveries of astronomy in the 1960s. It has a fairly stable and short pulse period. It is generally believed to be a rapidly rotating neutron star or a neutron star that is rapidly rising and falling. The density of matter inside a pulsar is unbelievably high. A piece of matter the size of a matchbox can weigh as much as 2 billion tons. Because it has such a high density of matter, and because of the constant interaction between the extremely strong electric and magnetic fields inside it, it is able to rotate rapidly without disintegrating.

Pulsar is a very strange star, it is constantly very regular outward radio pulses, always very regular radio signals, like a pulse. The pulses of different pulsars have long and short periods, with the long ones lasting several seconds and the short ones lasting only a few tenths of a second, while the pulse period is very precise.

Why do radio waves from pulsars have precise periods? It is generally believed that the neutron star light has a structure called "lighthouse" (is some of the more concentrated areas of radiation), constantly emitting strong radio waves, the neutron star every week of rotation, the "lighthouse" towards us once, people will receive a radio wave.

Pulsar is who found in August 1967, Cambridge University Professor Ish and graduate students Bell in the observation of an area of more than 20,000 square meters of the huge antenna array of radio sources, accidentally recorded a pulse image. This was so puzzling that the observers wryly remarked that it was "a signal from the little green man". After a period of repeated observations, it was determined to be a special new type of object -- pulsar.

The pulsar is called CP1919 (CP is the abbreviation for pulsar discovered by the University of Cambridge, and 1919 is the star's coordinate number), and its pulse period is 7.337301344 seconds, accurate to nine decimal places! That means it's accurate to one hundred millionth of a second! That's 20 times more accurate than a cesium atomic clock.

Later, the United States, Australia and other countries have observed many more pulsars, up to now there are more than 330.

The name of the pulsar is called a star, in fact, even with the largest optical telescopes can not see it, and usually only with radio telescopes to receive its pulsed signal.

Generally, pulsars are found to have only radio pulses, while some are found to have optical pulses as well. China's ancient observation record of the 1054 superstar outburst provides valuable information on the formation and evolution of pulsars.

In the early morning of a day in July 1054 during the Song Dynasty, astronomers from the Chintian Supervisory Commission saw an amazing celestial event. A celestial body brighter than Venus appeared in the east for 23 consecutive days and could be seen during the day. The brightness then gradually diminished, and it took more than 60 days before it became completely invisible. The history of the Song Dynasty recorded the beginning and end of this guest star, calling it the "1054 Tian Guan Guest Star". After its outburst, it left a cloudy remnant, which, when photographed with a telescope, resembled a crab, and was therefore called the Crab Nebula. It is still constantly sending radio waves in all directions.

Scientists believe that the Astronomical Clock is the most accurate clock in the universe, and that a pulsar could replace the Atomic Clock as a timepiece for interstellar flights in future space expeditions.