Laojiu in the solar system is a black hole？ It is bold to guess, but difficult to verify.

　　NASA

　　Pluto, once "Laojiu", has now been "reduced" to a dwarf planet.

　　Our reporter Gao Bo

　　Not long ago, two foreign astronomers put forward a bold idea: the ninth planet in the solar system, which is "hidden from time to time", is likely to be an original black hole.

　　There is a black hole in the solar system that controls distant celestial bodies? Some experts said that this is an interesting hypothesis, but it is difficult to confirm or falsify with the current observation ability.

　　The vacant throne, there are new contenders.

　　More than a decade ago, who was the ninth planet was clearly written in the textbook. In 1930, clyde tombaugh discovered PLUTO, equating it with Uranus and Neptune, giving it the magnificent Greek name "Prouteau", and the nine planets in the solar system became a kind of common sense knowledge.

　　However, scientists later realized that Pluto seems to be "far from enough to see" in the outer space of the solar system. Since 1992, some distant ice-stone structures have been discovered one after another, and their volume is similar to Pluto. In 2005, it was discovered that the planet Eris was 27% more massive than Pluto! Pluto can be counted as the ninth largest, and it’s unreasonable that Venus doesn’t rank tenth.

　　Astronomers made a decisive decision, and the 26th International Astronomical Union held in August, 2006 passed a resolution: Pluto was classified as a dwarf planet and removed from the nine planets in the solar system. Prouteau abdicated tragically and became an asteroid 134340.

　　But the throne of the ninth planet is not so easy to cancel. In recent five years, some new discoveries have led people to speculate that there may be a real "P9" (the ninth largest planet) in the solar system.

　　On September 24th, another newcomer joined the battle for the throne — — ArXiv.org posted a paper, and Jakub Scholtz of Durham University in Britain and James Unwin of the University of Illinois in the United States put forward a bold idea: the ninth planet in the solar system may be an original black hole.

　　Strange orbit, pointing to the hidden "P9"

　　Around 2014, astronomers discovered some celestial bodies in the Kuiper Belt (the area near the ecliptic plane outside Neptune’s orbit). When the orbit is far from the sun, it can reach hundreds of astronomical units (one astronomical unit is the distance between the sun and the earth). At first, this was explained as the gravitational scattering effect of Neptune. But soon, the conjecture of the new ninth planet was put forward.

　　In 2016, michael brown of California Institute of Technology and his colleagues discovered that six celestial bodies in the Kuiper Belt have strange orbits, and their perihelions all point in the same direction. It’s like six clocks that turn at different speeds, but the hands all point in the same direction. If Neptune was behind the scenes, their directions would have been scattered and not so concentrated.

　　Moreover, when the six celestial bodies are closest to the sun, the distance is more than 40 astronomical units, and the Neptune hypothesis is not easy to explain.

　　Michael brown and his colleagues calculated that the probability of "big guys pointing to accidental coincidence" is 0.007%— — It is more realistic to believe that there is a "big guy who has not yet appeared".

　　Zhou Liyong, an astronomer and professor at Nanjing University, said in an interview with Science and Technology Daily that many people opposed the existence of "P9" at first. With the continuous discovery in recent years, the statistical significance of confirming the existence of the ninth largest planet has gradually increased.

　　Although "P9" has not been observed, some people have speculated its parameters through computer simulation: it is 200 to 800 astronomical units away from the sun, and its mass is 5-mdash that of the earth; Ten times, it takes 30,000 years to circle the sun … …

　　It is not necessarily the earth that wanders, but it may also be a black hole.

　　Astronomers used to believe that the possibility of a new planet outside Neptune is very small, because the material in this area is too thin, and it takes too long to grow a big planet. But what if the solar system "plundered" a ready-made planet from the vast universe? This possibility is worth considering.

　　"In fact, there may be many wandering planets in the universe, just like in the movie ‘ Wandering earth ’ Same. " Xie Jiwei, an astronomer who studies extrasolar planets and an associate professor at Nanjing University, told the Science and Technology Daily reporter that one way to find extrasolar planets is called gravitational microlensing method, which is to capture the weak deformation of images — — The light is distorted by the mass of a celestial body along the way to find clues about the existence of exoplanets. In this way, we have observed many "clues", indicating that there are many "tramps" who are unorganized and undisciplined in the unknown darkness.

　　In the suspected area of "P9", the gravitational anomaly was observed in the optical gravitational lens experiment (OGLE). At least six gravitational microlensing events indicate the gravity anomaly in this area, suggesting the existence of a free-floating celestial body with a mass range of 5-mdash; Between 15 earth masses. The conjecture of "P9" is therefore encouraged.

　　The new paper by Schultz and Unwin speculates that this celestial body may not be a rogue planets, but a wandering black hole. It was drawn into the group by the solar system, which disturbed the orbit of the outer celestial bodies.

　　Generally speaking, black holes observed by astronomers are gathered after the death and collapse of stars. The original black hole that exists in the theoretical assumption is another matter. Hawking made a great contribution to this concept: it was a "cultural relic" that came into being shortly after BIGBANG.

　　The universe before the Big Bang was called the primordial universe by astronomers. The explosion of the original universe was uneven, and the energy density in the local space was too high. Without collapsing, it was compressed into points with infinite mass and surrounding black holes. This kind of black hole varies in size, and it may be as small as a particle. The general primary black hole is similar in mass to the common asteroids in the solar system.

　　These black holes then drift around the universe. Some are dissipated by Hawking radiation and melted like ice; Others absorb substances and grow, and survive to this day.

　　Schultz and Unwin pointed out that the abnormal orbits of celestial bodies outside Neptune, as well as some gravitational events, can be explained by the original black hole whose mass is several times that of the earth; An original black hole may be captured by the solar system and become the ninth planet; They proved that the possibility of this capture is worth considering.

　　Strict assumptions, there are still many voices of opposition.

　　"The idea of this paper is still very rigorous and standardized, not a guess." Xie Jiwei said, "but the author also said that this is only a possibility. Introducing the concept of black hole may be interesting and strange to everyone. But the next step is still impossible. Moreover, whether there is the ninth largest planet is still a problem. "

　　Schultz and Unwin said that if "P9" is an original black hole, it may pass through the peripheral "halo" — — The positive and negative electrons in the outer layer of a black hole annihilate the light to determine its existence. However, a planetary scientist told the Science and Technology Daily reporter that such observation is difficult to achieve because the black hole is small and uncertain in its location.

　　"I personally don’t like the idea of the original black hole." An expert engaged in planetary research told the Science and Technology Daily reporter, "It feels almost mystical — — Can explain some phenomena, but basically never see it. "

　　"The discoverer of Kuiper objects, David Jewitt, didn’t even believe in ‘ The ninth planet ’ The existence of. " The expert said that David Jewett said in a TV interview that he didn’t think "P9" existed. He believes that the black hole hypothesis reveals that scientists are eager to make "major discoveries". But this theory is far from the stage of verification.

　　An important reason for different opinions is that it is still difficult to observe celestial bodies outside Neptune at the current level of human technology. Although humans have observed thousands of extrasolar planets.

　　"I don’t know the true face of Lushan Mountain, but I am only in this mountain." Xie Jiwei said, "Observing exoplanets basically infers the situation of planets indirectly by observing the Ling Xing effect or Doppler effect of star spectra. The planets in the solar system can be directly observed. The brightness of a planet is inversely proportional to its distance from the sun. Celestial bodies that are too far away will receive weak light and reflect weaker light. "

　　The periphery is so vast and the celestial bodies are so dim. Beyond hundreds of astronomical units, it is still unknown.

　　Xie Jiwei said: "Many celestial bodies on the edge of the solar system were seen through the Hubble telescope; After the Weber telescope works, our observation level will improve a little. "