“The dragon raises its head”, at what time does it raise its head?

February 21st marks the day when the Dragon raises its head. According to astronomical science experts, this year's Dragon raises its head around 10 p.m. What does "Dragon raises its head" mean? At what time can we see it?

Wang Kechao, the director of science popularization at the Purple Mountain Observatory of the Chinese Academy of Sciences, introduced that in order to observe celestial phenomena, ancient Chinese people divided the stars in the celestial equator and the ecliptic into 28 star groups, called the 28 Mansions. Among the 28 Mansions, each group consists of seven: the eastern one is the Azure Dragon, the southern one is the Vermillion Bird, the western one is the White Tiger, and the northern one is the Black Tortoise.

"The Eastern Azure Dragon includes seven constellations, namely Jiao, Kang, Di, Fang, Xin, Wei and Ji, which vividly outline the image of a dragon: Jiao is the head of the dragon, Kang is the neck, Di is the chest, Fang is the belly, Xin is the body, and Wei and Ji together represent the tail of the dragon." Wang Kechao said, "The Dragon Raising its Head" reflects the image of Jiao rising from the eastern horizon, as if the "head of the dragon" has been raised.

About 2,000 years ago, the ancient Chinese saw the "Dragon Raising its Head on the Second Day of the Second Month" shortly after sunset. Due to the precession of the equinoxes, people today generally see the "Dragon Raising its Head" at around 8 or 9 p.m. on the second day of the second month of the lunar calendar.

This year, the time to see the "dragon raising its head" is relatively later, around 10 o'clock in the evening. Wang Kechao explained that in addition to the influence of the precession of the equinoxes over the years, the time when the same stellar phenomenon appears in a day is also related to the early or late Gregorian calendar date. The same star rises about 4 minutes earlier every day than the previous day. The second day of the second month of the lunar calendar this year corresponds to the Gregorian calendar date of February 21. The time of "dragon raising its head" on that day is more than an hour later than "February 2, dragon raising its head" on March 14, 2021.

In the nearly two months after the second day of the second lunar month, the public can see the "dragon head" Jiao Su rising from the horizon at different times of the night. It takes about 6 hours for the entire "Cang Long" to rise from the horizon. From mid-July to mid-October of the Gregorian calendar, the public can see the entire "dragon shape" of Cang Long appear in the night sky after dark.