Knowledge about Pluto.

Listen carefully: among the nine planets, Pluto is the farthest from the sun and has the smallest mass. It hobbles in the cold and dark space 5.9 billion kilometers away from the sun, which is very similar to proto, the god of the underworld in Roman mythology. So people call it Pluto, which is the first two letters of the English name of Pluto in astronomy, and the abbreviation of the name of Lovel, an American astronomer who promoted the discovery of Pluto.

Pluto is the latest planet to be discovered. Compared with the discovery of Uranus and Neptune, the discovery of Pluto is "a lot of trouble". Pluto's brightness is very weak, only 15 and so on. Even in the photos taken by large telescopes, it is no different from ordinary stars. Finding it among thousands of stars is like looking for a needle in a haystack.

In the process of searching for Pluto, Lovel, an American astronomer who is an astronomy enthusiast, calculated the position of this unknown planet in detail and searched it carefully with a telescope, which took more than ten years. Until19161.0616 suddenly died.

1925, Lovel's brother donated a large-field photographic telescope with a diameter of 32.5 cm, which provided excellent conditions for continuing the search for new planets. From 65438 to 0929, the director of Lovel Observatory invited clyde william tombaugh to join the search for unknown planets. They searched one by one, photographed a large number of negatives, and examined each one carefully. This job is hard and boring. 193065438+1October 2 1 day, Tang Bo finally found this new planet in the negative of Gemini.

Mass: 0.0024 Earth mass

Radius:1350km

Period: 90465 days

Half-length diameter of orbit: 39.87 astronomical units.

Track eccentricity: 0.256

Orbit inclination: 17. 1.

Strange footprints

Pluto was once considered as a planet outside Neptune's orbit at the beginning of its discovery, but it turns out that it is not. For example, from1979 65438+1October 2 1 to 65438+March 0999 14, Pluto is closer to the sun than Neptune. This is because Pluto's orbital eccentricity and inclination to the ecliptic plane are greater than those of other planets. Pluto is closer to the sun than Neptune at perihelion, and Neptune becomes the farthest planet from the sun. Every once in a while, Pluto and Neptune will approach each other, and the orbits of the two planets will cross on the ecliptic projection map. But there is no need to worry about their collision, because their orbital planes do not coincide, and even near the intersection, the distance between them is still very large. They will fly by like vehicles driving at a fork in the road.

The appearance of satellites

1In July, 978, Christie of the U.S. Naval Observatory, while studying photos of Pluto, happened to find that Pluto's small round surface was slightly elongated. He found all the photos of Pluto since 1970, and found that this phenomenon appeared regularly, so he concluded that Pluto has satellites. Because Pluto is too far away from us, it is impossible to separate Pluto from its satellite in a large telescope. It's like an anemometer at a weather station. The crossbar connects two balls and rotates in the high wind. From a distance, when two spheres are combined into one, only the changes of its time circle and time plane can be detected. Pluto's moon is named Ka Rong. In Greek mythology, Chalong was a serviceman in prout, who devoted himself to crossing the dead in the ghost sea. Chalong period of revolution and Pluto have the same rotation period, which is 6.39 days.

What is the diameter of the ghost king star?

Because Pluto is too dark and too small, it is impossible to determine its size for a long time after its discovery. At first, it was estimated that its diameter was 6600 kilometers, and it was changed from 1949 to 10000 kilometers. 1950, kuiper revised it to 6,000 kilometers with a newly-built 5-meter telescope, 1965, and limited the diameter to 5,500 kilometers by using Pluto to cover the stars. 1977 It was found that the surface of Pluto was frozen methane. According to its albedo, the diameter of Pluto is reduced to 2700 meters. 1980, the 3.6m infrared telescope on Monaque Mountain measured Pluto's diameter at 2600-4000km and Chalong's diameter at 2000km. In recent years, some astronomers have observed that the diameter of Pluto is about 2,400 kilometers, which is smaller than the diameter of the moon (3,475 kilometers), while the diameter of Chalong is 1 180 kilometers, which is the largest ratio of planets to satellites among the nine planets. So some people say that Pluto and its satellites are more like a two-planet system.

An unknown number of planets

Pluto has only been discovered for more than 60 years, plus it is small and far away, which is the most unknown one in the planet at present. The 1970s and 1980s were the golden ages of space exploration in the solar system. Eight of the nine planets have been approached by interplanetary probes, and only Pluto is a blind spot where spacecraft have not set foot. In the list of planetary parameters given by various astronomical books and periodicals, Pluto leaves the most blank. Even if the data are listed, many of them are marked with question marks, indicating inaccuracy.

In addition to a series of unknowns, people also have questions about Pluto's identity. Pluto has the smallest diameter and mass among planets, with a density of .8 ~ 2.1g per cubic centimeter and an albedo of 50% ~ 60%, which is similar to several large satellites of other planets. Is a ghost satellite a planet or a satellite? Or a big asteroid? However, whatever it is, as a celestial body on the distant boundary of the solar system, its mystery has great attraction to astronomers. I believe that in the near future, with the development of exploration technology, Pluto will become a hot topic in planetary astronomy.

Are there any alien stars?

When Copernicus proposed Heliocentrism, Saturn was the boundary of the solar system. Later, with the discovery of Uranus, Neptune and Pluto, the boundaries of the solar system extended again and again. However, in theory, the solar system should be 100 times or even 10,000 times larger than the nine planets. Are there any extra-terrestrial planets in the solar system? In this regard, astronomers have done very extensive and arduous work. During the 14 years after the discovery of Pluto, Tobo has been looking for extraterrestrial planets by looking for Pluto. He carefully examined 362 pairs of negatives with a flash comparator (these negatives account for about 70% of the whole day), looking for possible new planets from each negative. He discovered many new celestial bodies, but there were no extraterrestrial planets. Scientists believe that if there is an extraterrestrial planet, it will inevitably disturb the detector flying near it, and its influence can be reflected in the orbit of the detector. However, after flying over the orbits of Neptune and Pluto, the Voyager probe operated normally and did not provide any clues to prove the existence of unknown objects. Whether there are extraterrestrial planets is still a mystery to be solved.

5.9 billion kilometers from the earth

For additional information, see New Horizon.