These days, a rapid rise of “net red” comet swept through the circle of friends. Astronomical enthusiasts all over the world hold up their observation equipment, and beautiful comet pictures appear one after another. It decorates the night sky in the northwest and our cyberspace. It is this year’s “black horse” comet, comet neowise.
when the comet was first discovered, it was at the base of the ship. It passed through Canis Major and Uranus in mid and late April, passed through kylin and Orion at the end of May, and moved from the south of the ecliptic to the north of the ecliptic at the end of June. In July, it passes through Auriga, tmall and Ursa Major. In August, it enters the spring sky, and comes into the constellation Altair, shepherd, and Virgo. After that, as we get farther and farther away from us, the brightness will get darker and darker, and it will not return until more than 6000 years later.
on March 27, 2020, the wide area Infrared Sky Survey Explorer Space Telescope discovered this object during its neowise mission. At that time, its brightness was only about 18 degrees, about 300 million kilometers away from the sun and 250 million kilometers away from the earth. In April 2020, the comet was named after the project name “neowise”, and the comet number was C / 2020 F3, where C represents that it is a long-term or aperiodic comet, and 2020 F3 means that it is the third comet discovered in the second half of March 2020.
today’s famous comet Xinzhi was actually a “little transparent” when it was first discovered. As it gets closer to the sun, comet Xinzhi is getting brighter and brighter. In the first ten days of June, it is close to the sixth grade. But as it moved to the back of the sun, the comet disappeared from view. It was not until half a month later that comet Xinzhi appeared again, and its brightness had reached 2.5.
in a short period of more than half a month, comet Xinzhi was invisible to the naked eye, and its brightness increased by about 100 times. Why does the brightness of the same comet change so much? In fact, the main reason is the distance between the comet and the sun.
the reason why comets can be seen is that they reflect sunlight. On the one hand, as the comet approaches the sun, the intensity of sunlight increases, so it looks brighter and brighter. On July 3, 2020, comet Xinzhi will reach perihelion, only about 43 million kilometers away from the sun.
on the other hand, the speed of the comet’s movement is accelerating, resulting in a longer tail of dust. So the closer a comet is to the sun, the brighter it looks. The energy of the sun heats the comet, and gas and dust erupt from the comet’s surface, forming a huge dust tail, which is generally yellow. At the same time, the comet will produce a stream of charged particles under the action of the solar wind, forming an ion comet tail, which is generally blue.
in July 1994, a comet wood collision shocked the world. Under the strong gravity of Jupiter, a comet named “shoemaker levy 9” broke into 21 comet nuclei, which “bombed” the surface of Jupiter in a few days. Such an impact still scares people – if this event happened on earth, it would be a devastating blow. So “early discovery and early treatment” has become one of the important purposes for scientists to study comets.
in addition, by observing comets, astronomers can also obtain a lot of valuable information, such as the proportion of gas and dust, the size distribution of dust particles, the isotopic abundance of some elements (such as hydrogen), the visible light spectrum of comet nucleus reflecting sunlight, the thermal infrared spectrum of comet itself, and the rotation state of comet nucleus.
astronomical observation is generally divided into two types, one is imaging photometry, the other is obtaining spectral data, so is comet observation. For astronomers, when a comet is very far away from the sun, it is difficult to directly determine whether it is a comet, which requires a large aperture Sky Survey Telescope with high sensitivity terminal equipment to obtain more information.
comets formed outside the snow line of the early solar system. It carries a lot of original information about the solar system, such as the hydrogen isotope abundance mentioned above, which is likely to be different at different locations in the early solar system. Although the shape, mass and orbit of different comets are quite different, they have a common feature: they all contain ice. The water on the earth is likely to come from the early comet collisions. By comparing the hydrogen isotope abundance of the water on earth with the data of different comets, combined with the orbits of various comets, scientists can constrain the early evolution model of the solar system.
comet Xinzhi is a very bright comet suitable for observation in the northern hemisphere in recent years. It can also be observed or photographed in the city on a good night. In the middle and late July, the brightness of comet Xinzhi dropped to below grade 3. If you want to enjoy this comet, you need to consider the following questions.
weather is particularly important for astronomical observation. Eastern China is located in the monsoon climate region. July is the season with the most rainfall. You can use the astronomical Weather software to query the weather and plan the observation time in advance. Of course, if there are conditions, it is recommended to select areas with high probability of sunny days for observation.
in addition, the highest altitude of comet Xinzhi is about 20 degrees after sunset, and then it will slowly decrease. Therefore, the northwest of the observation area is relatively open. In the city, you can choose to observe in the park or higher floors. In the area where the comet can be seen all night, it is relatively open from northwest to northeast, especially due north.
the beauty of a comet lies in its tail. However, even in places where the observation conditions are relatively good, it is difficult to directly see the comet tail with the naked eye. Some equipment is needed to assist observation, such as binoculars. It’s portable and affordable. It is recommended that you use 7×50 mm or 10×50 mm binoculars (the number in front of X is the multiple, and the number behind x is the aperture). The price ranges from 500 yuan to 1000 yuan. In addition, it is recommended to purchase a special bracket for binoculars, so that the binoculars can be installed on a tripod to enjoy the comet slowly and avoid overwork on both hands.
the biggest difficulty in using binoculars to observe comet Xinzhi is how to “aim” the comet. We can use the electronic star map to determine the position of the comet in advance, and then use the star bridge method or the surrounding bright stars to locate it. For example, at 21:00 on July 21, 2020, the location of comet Xinzhi is just below Tianxuan, the Big Dipper star. You can use binoculars to find Tianxuan first, and then look down vertically. It is easy to find the comet.