What are the difficult journeys for people to find planets?

Exploring the sky far away from the earth where we live is a diligent and exciting thing in history. In the 4700 years since Sumerians discovered the seven "planets" such as the sun, the moon, mercury, Venus, Mars, Jupiter and Saturn in 3000 BC, no one has ever made a breakthrough discovery (not including comets here). People think that since all known planets can shine, if there are other planets, people should find them easily. So, how can there be undiscovered planets? So people arbitrarily judge that there will be no new discoveries.

It has been known for a long time that planets themselves do not emit light. The ancient Greeks first discovered that the moon was just a non-luminous star by observing it. After the invention of the telescope, people can't shine when they observe Venus and Mercury. So it is inferred that all planets can't shine, but only reflect sunlight.

According to this inference, we can draw a conclusion: the farther away from the sun, the smaller the planet is, so the less sunlight it receives and the less light it reflects, and the less likely it is for us to observe the planet from the ground. If there are other planets besides Saturn, and this planet is smaller than Saturn, then the sunlight it reflects may be very dim and cannot be observed on the earth. In addition, the farther the planet is from the sun, the slower its revolution speed and the longer it will be hidden behind other stars.

All this seems obvious now, but for astronomers at that time, even with advanced equipment such as astronomical telescopes, they still insisted that all the planets could "emit" strong light, but those stars twinkling in the sky failed to attract their attention. In fact, they completely ignored the possibility that those stars were planets.

178 1 year, and finally discovered a new planet by accident. The discoverer's name is William Herschel, but a professional musician loves astronomy. He always wanted to own an astronomical telescope, but he couldn't afford the high cost, so he made one himself. The performance of this telescope was higher than that of other telescopes at that time. It was with this self-made telescope that William Herschel accidentally discovered a shining star, which looked like a planet from its disk shape, but it did not attract William Herschel's attention at first. He thought he had found a new comet, but the comet dragged a long "tail", and the shape of the new star was very obvious, and the moving speed in the sky was extremely slow and practical. Later, people named it Uranus. Its revolution radius is about twice that of Saturn, which is 2.87 billion kilometers, so it reflects very little sunlight, which is almost invisible to the naked eye on the earth.

The eighth planet discovered is Neptune. Unlike Uranus, Neptune was discovered by mathematical calculation. The first attempt to determine the orbit of Uranus was made by Jean-Baptiste Drabo after he discovered the planet in 1790, but even considering the influence of Jupiter's gravity, the orbit is quite inaccurate.

British mathematician john couch adams and French mathematician Yu Erban Levell further studied the disordered state of Uranus orbit. Adams suspected that something had pulled Uranus out of its orbit. 1845+00 In June, he sent his calculation results to Sir George ellery, a British astronomer, and described the position of a possible new planet. Ellery doesn't know this young mathematician. According to the tradition at that time, he asked Adams a simple math question to test his math ability, but the question was not answered and the matter was put on hold. Unfortunately for Adams and ellery, Adams' calculation of the position of the planet was only 2 degrees away from the correct value.

At the same time, Levell, who didn't know what Adams had done, was also studying the same problem. However, his calculation result is only 1 degree away from the accurate value. Levell was also more active than Adams in propagating his ideas. He published his work 1846 in June. Ellery had Adams' calculation results in his hand, so he sent Levar his usual question-a simple math problem to test Levar's math ability. When Leverrell sent back the correct answer, he believed that he had done it right. This is the calculation result of a real possible planet.

Ellery passed Levar's information to Challis, director of Cambridge Observatory, in order to find the so-called planet. However, it is difficult (if not impossible) to find a suitable star map at this time, and the accuracy hinders the discovery of planets in the predicted position (Aquarius). Jonas Gali and Heinrich Ludwig Darrist of the Berlin Observatory accepted Levar's request one month after they devoted themselves to discovering this planet in Challis, and inspected this testing ground in the constellation on September 23rd, 1846. That night, Gary and Darryl discovered the planetary disk, Neptune, named after the king of the sea.

The discovery of planets outside Saturn's orbit further stimulated astronomers' enthusiasm for exploration. However, it took only a century for mankind to discover the last planet on the list of planets we currently have.

The discovery of Pluto, like Neptune, is a major exploration, which was completed after years of calculation and thinking. After the discussion on the orbits of Uranus and Neptune subsided, several astronomers still thought that the matter was not over, especially Neptune Q was disturbed. Many astronomers, including William H Pickering and percival Lowell, are chasing the fashion of astronomy. They pointed out that the gravity of the ninth planet exists outside Neptune's orbit (today, we have clearly pointed out that many so-called disturbances come from the error of original observation; In addition, when our closer measurements of Pluto continue to show that it is smaller than previously thought, astronomers have understood that the irregularity of Neptune's orbit has nothing to do with Pluto.

In fact, it was the solution of the disturbance problem of Lowell's planet that led to the actual discovery of Pluto. Lowell predicted that Gemini has a planet, the mass of which is about 6.6 times that of the Earth, and it is the "X planet" outside Neptune's orbit. Lowell inspected this unknown celestial body at his Arizona Observatory (now Lowell Observatory in flug, Arizona) for 65,438+00 years, until he died in 65,438+0,965,438+06, and failed to find the planet.

Lowell's dream didn't disappear with the death of the astronomer. His three loyal assistants continued his work, namely V.M. Silver, C.D. Lampland and E.C. Silver.

However, due to property litigation and lack of funds, it is difficult to continue this exploration. Finally, with the support of Lowell's nephew Roger Lowell Putnam, the Observatory changed into a 33mm photographic telescope (Lawrence Lowell Telescope, now called Pluto Telescope) in 1929, which can take a single photo of the sky interval of 12 times 12 degrees. Exploration began in Gemini, but it is a big problem to overcome the star quality of this constellation (near the milky way star fog). However, there is still hope that the flicker in the microscope is similar to the microscope used by Max Wolf to discover asteroids when1photography appeared in the late 8th century.

From 65438 to 0929, astronomer Creed Tombaugh devoted himself to finding planets other than Neptune at Lowell Observatory. He works under the guidance of v.m. silver. Pairs of photos taken by Lowell telescope are compared with the scenery in scintillation microscope. This microscope quickly transforms two scenes of the same star position taken at different times, and the moving cosmic objects appear "flicker" and jump back and forth under a fixed star background.

Pluto is the only planet discovered in this century, which leads to a very exciting discovery story. The most important images taken by 65438+ Lowell Telescope on the night of 23rd and 29th of 0930 1 month.

In his book out of the dark (co-authored with Patrick Moore), Tombaugh wrote: (1930) 18 On the morning of February, I put the photographic negatives of 65438+1October 23rd and 65438+1October 29th on the scintillation counter. This is the luckiest decision. Otherwise Pluto would not have been discovered in 1930.

Before 4 pm that day, I covered 1/4 of the image pair. After I finished the left half of the horizontal video tape, I turned the horizontal sliding frame to the center line of the north-south direction (I always draw a thin ink line on the negative film taken after the image is centered). I got into the habit of moving them to the left when I was working, so that I wouldn't forget what to do when someone disturbed me ... I lifted the eyepiece device to a horizontal belt, and on the center line, I placed a "triangle jewel" indicator star in the small rectangular field of vision of the eyepiece. After scanning several scenes to the left, I turned the next scene into my sight. Suddenly, I saw an image of115 apparent magnitude bouncing out and disappearing in the rapidly alternating field of vision. Then I look at other images on the left 3 mm (or 0. 125 inch) and do the same. "That's it!" I said to myself loudly. So which image belongs to which negative? I turned off the automatic flash on the camera and turned the shutter back and forth with a small mechanical lever. The image on the right is on the first film (65438+123 October), and the left hand in the field of vision is the west. Then, I set the shutter to 65438+1the negative on October 29th for observation, and this image appeared on the left of other images. Reverse rotation is also possible. If the offset direction is to the east, these images are scattered, or two erratic stars happen to be caught while changing states alternately. Considering the distance between the substrates, its parallel displacement indicates that the object is far away from Neptune's orbit, perhaps 65.438 billion miles away! The target is a new planet, which lies outside Neptune's orbit, about this distance. This discovery was announced on March 1930 13. This new planet with a size of about 2,280 kilometers (the latest calculation) was named Pluto, named after the mythical figures in the underworld.

Of the eight planets around the sun and the earth, five are visible to the naked eye: Mercury, Venus, Mars, Jupiter and Saturn. The other three planets-Uranus, Neptune and Pluto-are hard to see without a telescope.

Mercury, Venus, Earth and Mars are sometimes called terrestrial planets. Because they are small, dense and hard. Therefore, you can land on their surfaces. Jupiter, Saturn, Uranus and Neptune are all giant air masses, which are not tight at all, just like hydrogen and helium balloons. If you want to land on their surface, you will be involved and finally crushed by its powerful airflow. These planets are called Jupiter-like planets. On the other hand, Pluto has no category at all. Small and far away, it is difficult to learn. It may be closer to the earth than Jupiter.