Rare astronomical phenomenon! Two conjunctions of "Mars" and "Venus" in 9 days

According to the popular science experts from the Purple Mountain Observatory of the Chinese Academy of Sciences, Juno, one of the largest asteroids in the asteroid belt, will conjunct Venus twice at 4:00 on September 13 and 7:00 on September 21. What is the matter with Juno conjunct Venus? Is it common for Juno to conjunct Venus twice in 9 days? Astronomy popular science experts reveal the secrets for you.

Wang Kechao, the director of science and technology at Purple Mountain Observatory, introduced that Juno is the third asteroid discovered by humans. It is located in the asteroid belt between Mars and Jupiter. Juno, Ceres, Pallas and Vesta are the four largest asteroids in terms of mass and volume among the known asteroids, and they are also the four earliest discovered asteroids. But compared with the moon, Juno is much smaller in size. In addition, its orbit is very far from the sun, and Juno's apparent magnitude is between 7.4 and 11.5, which cannot be observed with the naked eye.

The definition of "conjunction" in astronomy does not mean that two celestial bodies actually move together, but refers to the fact that the geocentric right ascension or geocentric ecliptic longitude of the two celestial bodies is the same. Specifically, when Juno and Venus are conjunct, it means that the geocentric ecliptic longitude of the two celestial bodies is the same.

"It is rare for Juno and Venus to conjunct twice in a short period of time." Wang Kechao explained that Venus began to turn from retrograde to direct motion at 11:34 on September 3, and at this time Venus moved slowly from west to east. On September 13, Juno surpassed Venus and the first conjunction occurred. As Venus accelerated, Venus surpassed Juno again on September 21, and the second conjunction occurred. It was as if the two celestial bodies were "overtaking" each other.

Wang Kechao said that the last time Juno and Venus were in conjunction was on March 19, 2023. After September this year, the next conjunction between the two will be on September 6, 2024.

In September this year, Juno and Venus met twice, and the angular distance between them was relatively close, so the public could only see the bright Venus with the naked eye. Wang Kechao suggested that if you want to observe Juno, it is best to use an astronomical telescope with an aperture of more than 100 mm. If you want to take a picture of Venus and Juno in the same frame, you can use a telephoto lens for a long exposure.

Planning: Liu Xinhui

Reporter: Wang Jueyin, Qiu Bingqing

Poster production: Xu Zhan

Editors: Chong Dahai, Zhu Shun

Produced jointly by Xinhua News Agency Domestic Department and Xinhua News Agency Jiangsu Branch

Produced by Star Studio