The streak of light in the sky of Da Nang and Quang Ngai this morning was caused by China launching the Tianzhou 9 spacecraft.

According to the National Center for Hydro-Meteorological Forecasting, the streak of light that appeared in the sky this morning was due to China successfully launching the Tianzhou 9 spacecraft from the Wenchang launch site in Hainan province.

A moving streak of light in the sky early this morning was captured by people in Quang Ngai - Photo: FB HUY NGUYEN

On the morning of July 15, social networks shared information and images of a moving streak of light in the sky early this morning.

"This morning, a strange phenomenon was seen all over the sky in Quang Nam (old), a long streak of light appeared with movement, causing people to panic" - shared a Facebook group of Duy Xuyen people.

Images and videos of the streak of light appearing in the sky were recorded by many people in the central provinces and cities such as Da Nang, Quang Ngai...

The National Center for Hydro-Meteorological Forecasting said that this phenomenon of bright streaks in the sky (seen from Vietnam) was due to China successfully launching the Tianzhou 9 spacecraft from the Wenchang launch site in Hainan province using a Long March 7 rocket.

China's launch time was 5:34 a.m. Beijing time (4:34 a.m. Hanoi time).

Weather expert Huy Nguyen also said that the image was filmed and taken in the sky area of the eastern central region at around 4:40 this morning, showing the Long March 7 rocket launching China's Tianchou 9 spacecraft into space.

The Long March 7 rocket is a hypersonic rocket (speed greater than 8,575 km/h) that will create a "sound wall" behind it. The white cone-shaped trail of gas behind a hypersonic rocket is called a condensation cloud or vapor cone.

The light streak was captured by locals at 4:39 this morning - Photo: NCHMF

According to weather expert Huy Nguyen, the white streak of light we see with the naked eye is due to four factors.

First , shockwaves. As the missile travels at supersonic speeds, it compresses the air ahead, creating shockwaves. These waves reduce the pressure and temperature of the air in certain areas behind the missile.

Second , water vapor condensation. Under the low pressure and temperature conditions caused by the shock wave, water vapor in the air condenses into tiny droplets, forming a white cloud. This cloud is usually conical in shape because the shock wave spreads in a cone shape (called the Mach cone) from the nose of the rocket.

Third , environmental conditions. This phenomenon is more visible in humid air conditions, when there is more water vapor to condense. If the air is too dry, the gas streak may not appear or be difficult to see.

Fourth , visual effects. The white trail is not smoke or burning fuel, but just condensed water vapor, so it often appears and disappears quickly as the rocket moves through air regions with different conditions.

The observer's perspective and the time of observation also show different image quality.

The National Center for Hydro-Meteorological Forecasting said this phenomenon occurs when rockets are launched at high altitudes, through the stratosphere or higher.

At that time, the exhaust gases from the rocket engine (including steam, propellant and chemicals) are exposed to sunlight from below the horizon. These particles will reflect the light, creating a white or brightly colored streak of light, stretching and spreading across the night sky.

WISDOM

Source: https://tuoitre.vn/vet-sang-tren-bau-troi-da-nang-quang-ngai-sang-nay-la-do-trung-quoc-phong-tau-vu-tru-thien-chau-9-20250715095354484.htm