Surprise! The "supermoon" will be here for the Mid-Autumn Festival. This year, you can "feast your eyes"

The bright moon rises over the sea, and the world shares this moment. As September approaches, the annual Mid-Autumn Festival is getting closer and closer to us.

On the night of the Mid-Autumn Festival, the full moon hangs high in the sky, and the family sits together, chatting about daily life. This beautiful reunion scene has been passed down in my country for thousands of years. This year, the highlight of "moon watching" will be particularly interesting.

According to Xinhua News Agency, two weeks from now, on September 18, which is the 16th day of the eighth lunar month, the second "supermoon" of the year will arrive. If the weather is good, a particularly round and plump moon will hang in the sky, providing a visual feast for the public.

The "super moon" in August this year. Photo by Lin Chenchen

To this end, on the eve of the Mid-Autumn Festival, Chao News reporters interviewed experts in the field of astronomy to preview the scientific principles behind moon-watching.

Supermoon helps:

"The moon is full on the 16th day of the 15th month"

We often say that "the moon is fuller on the 16th day of the first lunar month". This year, with the help of the "supermoon", we can enjoy the moon with our family from the Mid-Autumn Festival to the next day, and even observe a bigger and brighter "white jade plate".

"The moon on August 16 of this year's lunar calendar will be the second closest moon to the earth this year," said Xu Yuhua, a popular science lecturer at the Zhejiang Astronomical Society. "In astronomy, there is no strict definition of a 'supermoon.' When the moon meets two conditions, namely, a full moon and at perigee, it can generally be called a 'supermoon.'"

Image source: Xinhuanet

In layman's terms, the moon usually orbits the earth in an elliptical orbit. When the moon is at its closest point to the earth, we will see the largest moon according to the principle of "bigger near, smaller far away". If the moon is full at this time, it will be the "big and round" effect that everyone likes to see. At the same time, statistics show that the brightness of the "supermoon" will be about 30% higher than the full moon farthest from the earth in a year.

According to astronomical predictions, the moon will be about 357,000 kilometers away from the Earth one day after the Mid-Autumn Festival this year. Compared with the average distance of 384,000 kilometers between the Earth and the Moon, it is about 27,000 kilometers closer. Therefore, to the naked eye, the apparent diameter will be larger and more impactful.

In addition to this year's Mid-Autumn Festival, "supermoons" will also appear on October 17 and November 15. Among them, the full moon on October 17 is the closest "contestant" to the earth this year, which is worthy of attention from astronomy enthusiasts and photography enthusiasts.

Where does the waxing and waning of the moon come from?

How to observe more beautifully?

Su Shi wrote in his Red Cliff Fu, "In the autumn of the year Renxu, the seventh month was on the 15th day of the seventh lunar month." The "full moon" here refers to the full moon on the 15th day of each lunar month, and the "full moon" refers to the day after the full moon.

Image source: Xinhuanet

In my country, the average cycle of the moon's waxing and waning is called the "synodic month". The first day of each lunar month is the "new moon day". On this day, the moon moves between the sun and the earth. From the earth, the moon and the sun rise and set at the same time, and the moon is submerged in the sunlight and cannot be seen. From this day on, we will slowly appreciate the different phases of the moon, such as the crescent moon, the waxing moon, the waxing gibbous moon, the full moon, and the waning gibbous moon, as the moon moves.

For ordinary people, how can we enjoy the moon more beautifully? According to the "Guide to Moon Viewing during the Mid-Autumn Festival" released on the official WeChat account of the Purple Mountain Observatory of the Chinese Academy of Sciences, the moon is most beautiful when it just rises from the horizon. At this time, the moonlight is scattered by the atmosphere and presents a warm yellow color. The night has not yet completely fallen, and the scenery on the ground can be vaguely seen and echoes with the moon. It is the best time to take pictures.

At the same time, the Guide states that due to the large longitude spanning from east to west in my country, the moonrise time will be gradually delayed from east to west in my country. The moon during the Mid-Autumn Festival will hang in the night sky all night, so even if you miss the moonrise, you can still watch it at other times.

It is worth mentioning that after the Mid-Autumn Festival, Zhejiang people also enjoy the "tide-watching day". "The tide on August 18 is the most spectacular in the world." The trumpet-shaped Qiantang River attracts many tourists every year to watch the tide because of its unique tide shape and scenery.

Because of the "mysterious power" of the moon, the tides are particularly strong on the 18th day of the eighth lunar month. "This is because when the moon is new or full, the sun, the earth and the moon are aligned in the sky, and the earth's oceans are subject to the greatest gravitational pull, resulting in the two largest tides each month," Xu Yuhua said. "Based on past experience, the two or three days after the Mid-Autumn Festival, combined with astronomical and meteorological factors, often usher in the largest tides of the year."