How did gold on the earth come?"Dig gold" together!

Author:Institute of Physics of the Ch Time:2022.08.11

LIGO (Laser interference gravitational wave observatory is a large -scale research instrument from the gravitational waves deep in the universe with the help of laser interference instruments.) In 2015, the first gravitational wave source GW150914 was detected in 2015.

Since then, the discovery of gravitational waves has sprung up. As of the end of 2018, LIGO has discovered 11 gravitational wave sources.

As of the end of 2018, 11 gravitational wave sources discovered

The above picture shows the basic situation of these 11 gravitational wave sources.

The blue and purple dots in the figure represent one of the black holes, while the yellow and orange dots represent the neutron stars. The number of vertical axes marked how many times the quality of these celestial bodies. The arrow in the figure represents two smaller celestial bodies and synthesize a large celestial body and release gravitational waves. Among them, 10 gravitational waves occurred in two black holes; only one gravitational wave incident, which was two neutron stars. Of course, this is also the first Gemini star observed in human history.

What we want to science is the two neutron stars and the incident. Because it answered a question that most Earth people would be interested in: How did gold come?

Gold is a metal monochrome composed of gold elements composed of the atomic serial number 79 (that is, 79 protons in the atomic nucleus). It has a beautiful golden yellow, and it does not have a chemical reaction with any other elements. Due to the scarce content and stable chemical properties, gold is often regarded as a legal currency in history and regarded as a symbol of wealth.

Picture source: PEXLS

But how did these gold come from? This problem has troubled human beings for thousands of years.

People have proposed a lot of weird conjectures: some people say that it is the sun that gathers, some say it is hardening water, and some people say that it is converted from cheap metals. Of course, we already know that these conjectures are not reliable. The earth itself cannot make gold, and all gold comes from heaven.

It wasn't until the second half of the 20th century that two astronomers found key clues to crack this century problem. They are Hoil and Forte we have seen earlier.

Before introducing the theory of Hoyle and Fuller, let's briefly review some basic knowledge about the evolution of star.

The sign of the birth of the star is the hydrogen nucleus fusion of the center area. At the main sequence star stage, there will be two cases of nuclear fusion in the center of the star: for small -quality stars like the sun, the end of the nuclear aggregation reaction is to produce oxygen elements; for large -quality stars exceeding 10 times the quality of the sun, The end of the nuclear aggregation reaction is to produce iron.

Why is the iron element at the end of the reaction of a large -quality star nuclear fusion? The figure below can explain the truth. The horizontal axis of this picture is the number of nuclear (nucleus containing protons and neutrons) contained in a certain atomic nucleus, and the vertical axis is the average combination of this atomic nucleus. The so -called average combination is the average energy required to combine each nucleus in the nucleus. As shown in the figure, among all chemical elements, the average combination of iron is the largest.

Iron has the largest average combination that leads to one consequence: iron is the most stable among all elements. In other words, all chemical elements that are lighter than iron becomes iron and will release energy; all chemical elements heavier than iron become iron, and they will also release energy. In other words, whether it is fusion or cracking into other elements, energy must be absorbed.

In this way, the nuclear fusion of the star center must be suspended after generating iron. Because the iron convergence of iron into heavier elements, not only cannot release energy, but also absorb energy. Such a sale of money will naturally not do it.

This leads to a consequences: heavier gold elements than iron elements, it is impossible to make through the form of stars center fusion.

Even the star center fusion cannot make gold, so how did gold come from? The answers of Hoil and Forter are from the outbreak of the supernova.

About the outbreak of supernova. One of the cases is the so -called "large -quality star collapse": During the collapse of the death of large -quality stars, the powerful gravity pushed the electron into the inside of the atomic nucleus, thereby combining with the proton to form a neutron; The process of childization will create a medium -sized bang, blowing all the outer material of the star, thus forming a supernova explosion. Hoil and Forter found that this is not all the stories of the supernova.

After the star "neutronization", the inside of the star became the "ocean" of the neutron. Because the neutrons are not charged, it is easy to fall into the iron atomic nucleus in the center of the star. In other words, the iron atomic nucleus can increase the number of nucleus in the nucleus by continuously capturing neutrons; at the same time, part of the captured neutrons will decline inside the atomic nucleus, and then change back to the proton again. This means that the number and neutron number in the iron atomic nucleus will increase, which will become a heavier element.

Relying on this method of "capturing neutron", iron can break through the bottleneck that cannot be converged into heavier elements, resulting in all heavy metal elements including gold and silver. The gold generated by the "neutron capture" process will spread out with the continuous expansion of the supernova, and integrate into the interstellar media. The interstellar media can form new stars and planets (such as our solar system and its eight planets). In this process, the gold in the interstellar media was brought to the earth. For a long time, people think that the outbreak of supernovas is the only way to produce gold. But in the 1990s, through computer simulation, astronomers found a very serious problem: Supernova eruption was actually a difficult thing.

As mentioned earlier, the outbreak of the supernova is the result of the explosion of the outer material of the star in the process of "neutralization". However, astronomers have found that in most cases, neutron explosions are not enough to explode the outer material of the star. In this way, there will be no more outbreak of supernova; large -quality stars will directly collapse into a black hole, and then disappear from the night sky silently. This is the "failed supernova". And the "failure supernova" cannot produce gold.

Due to the existence of "failure supernova", the outbreak of the supernova is not enough to produce all the gold in the universe. According to the estimation of astronomers, the gold produced by supernovas only accounts for 10%of the total gold in the universe. So how did the remaining 90% of gold come from?

In fact, as early as the 1970s, American astronomers Latimo and Schraim found the key clues of this problem, which is the coincidence of two neutron stars. In the process of colliding between the two neutron stars and then merging, they will throw out part of the material of some neutron stars outward. These throwing neutron substances can emit a large amount of electromagnetic waves at high temperatures, which greatly increases its brightness. Although it is far inferior to super new stars, its brightness can still reach 1,000 times that of ordinary new stars (probably equivalent to tens of millions of times of the sun's brightness). Therefore, people call it "thousands of new stars".

Thousand New Stars

Latim and Schraim found that the phenomenon of "neutron capture" could also occur during the combination of double neutron stars. The neutron substance that was thrown out contains many iron elements. In this way, the iron atomic nucleus can continue to capture neutron, thereby creating all heavy elements including gold. Unlike the supernova, there is no obstruction of the outer material when the double neutron stars are co -med, and there is no possibility of failure at all.

Therefore, the double -neutron star can produce more gold that erupted than the supernova.

For decades, human beings have not observed thousands of new stars that have been produced by double neutron stars, so it is impossible to verify whether this theory is correct. This situation has changed thoroughly on August 17, 2017.

On August 17, 2017, a carnival appeared in the astronomical community. At 12:41 that day (when coordinating the world), the Fermi Space Telescope sent a text message to the ground, saying that it had just detected a gamma ray violence from the depths of the universe.

In just 6 minutes, LIGO also news came, saying that it was detected at a time when the Gamma rays just mentioned were not much different, and a gravitational wave explosion event was also detected. Not only that, LIGO also determined the approximate range of this gravitational wave source, and sent the news to the telescope control center around the world at 13:21. The telescope all over the world pointed to the same direction at the same time, and really found a thousand new stars produced by double neutron stars in the NGC 4993 galaxy, which is 130 million light years away from the earth.

The rough position of the double neutron star

Astronomers all over the world are boiling. This is the first time in human history that a celestial body has emitted electromagnetic waves and gravitational waves at the same time. This discovery has opened a new era of multi -meal astronomy.

Of course, this discovery also verified the theory of double neutron stars and producing gold. According to the estimation of astronomers, the double neutron star and the incident can produce about 1.8 × 1024 ‍ tons of gold, which is about the total quality of 300 earth. I don't know who will fall into whom will fall into the pocket.

Author: Wang Shuang

Part of the map source network in the text

Edit: Zhang Runxin

Reprinted content only represents the author's point of view