China News Service, Beijing, June 14th (Reporter Shangguan Yun) "When will the moon appear? Ask the sky for wine." Throughout the ages, the moon has entrusted people's thoughts and good wishes.
On the evening of June 14 (May 16 of the lunar calendar), a "super moon" will appear in the night sky, which is also the "second full moon" this year.
This news has attracted the attention of many astronomy enthusiasts, and the topic of "super moon" has also appeared on the Internet.
What is a supermoon?
Is this situation mysterious?
Is it a rare celestial phenomenon?
A reporter from Chinanews.com interviewed Zheng Jie, an assistant researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.
He said that how to define a "supermoon" depends on the time difference between the time of the full moon and the moon's arrival at perigee.
Data map: Beijing, the first "super moon" will appear in the night sky in 2021.
Photo by China News Agency reporter Sheng Jiapeng
What is a "supermoon"?
To put it simply, two basic conditions need to be met to form a "super moon", one is "closest" and the other is "most round".
"Supermoon is a term proposed by American Richard Noelle." Zheng Jie explained that since the moon's orbit around the earth is elliptical, when the moon reaches perigee, the apparent diameter of the moon viewed from the earth reaches the maximum. .
If it happens to be a full moon at this time, it is called a supermoon.
In contrast, when the moon's apogee coincides with the full moon, it is also called a super small moon.
In addition, Zheng Jie said that the moon is the only natural satellite of the earth, and it is also the natural celestial body closest to the earth. Many celestial phenomena are related to the moon, and the most typical ones are solar and lunar eclipses.
Data map: The astronomical scene of the "supermoon total lunar eclipse" taken in Fuzhou City, Fujian Province (light generation to recircularization stage).
Photo by China News Agency reporter Zhang Bin
"In addition, when the moon moves on the celestial sphere, it will always obscure some famous bright stars or planets, so there are many opportunities for lunar occultation."
Is it rare?
A bright moon hangs in the night sky, which is pleasing to the eye.
However, supermoons are not a particularly rare phenomenon.
"How to define a supermoon depends on the time difference between the time of the full moon and the moon's arrival at perigee." Zheng Jie mentioned that because the probability of the two strictly overlapping is very small, in recent years, as long as the interval between the time of the full moon and perigee is less than For 24 hours, it will be regarded as a supermoon.
By this standard, there are usually 4-6 supermoons per year.
At 19:52 on June 14 (Beijing time, the same below), the first "super moon" of this year will appear.
The moon passed perigee at 7:23 on June 15, and the difference between the two was less than 12 hours.
Additionally, the July 14 full moon occurred less than 10 hours after the lunar perigee.
Therefore, Zheng Jie said that this year's "biggest full moon" will appear on July 14 (the sixteenth day of the sixth lunar month).
Data map: A super full moon appeared in the Dunhuang night sky in the ancient county of Gansu.
The picture shows the full moon in the desert in the Crescent Moon Spring Scenic Spot of Mingsha Mountain.
(Multiple exposure) Photo by Wang Binyin issued by China News Agency
How to observe?
Generally speaking, on the night of the "supermoon", it can be observed anywhere as long as it is sunny or less cloudy.
Or, when viewing the supermoon, you can use ordinary binoculars or monoculars, or even a DSLR with a telephoto lens.
"The lunar orbit is an ellipse. According to measurements, the moon is about 363,000 kilometers away from the earth when it is at perigee, and about 406,000 kilometers when it is at apogee, with a difference of about 11%." Zheng Jie explained.
"So, compared to the two, the apparent diameter of the full moon at perigee is 12-14% larger. But there is only one moon in the sky. If there is no suitable reference, it is actually more difficult to see the difference simply by relying on the naked eye." (End)