DA NANG – Early this morning, around 4:40 AM, residents in the city of Da Nang, Quang Ngai province, and surrounding central Vietnamese areas witnessed a spectacular and unusual streak of light stretching across the eastern sky. Images and videos of the phenomenon quickly spread on social media, sparking widespread curiosity and speculation.
Shortly after, authorities and experts confirmed that the light was the result of a rocket launch from China.
Rocket Launch Details
Mission: The launch of the Tianzhou-9 cargo spacecraft.
Purpose: To deliver supplies, experimental equipment, and fuel to China's Tiangong space station, which is currently in Earth's orbit.
- Launch Vehicle: A Long March-7 Y10 rocket.
- Launch Time: 5:34 AM Beijing Time (which is 4:34 AM Hanoi Time) on July 15, 2025.
- Launch Site: The Wenchang Spacecraft Launch Site, located on Hainan Island, China.
According to a statement from the China Manned Space Agency (CMSA), the launch was a complete success. Approximately 10 minutes after liftoff, the Tianzhou-9 spacecraft successfully separated from the rocket, entered its predetermined orbit, and deployed its solar arrays.
Why Was It Visible from Vietnam?
The primary reason the phenomenon was visible from Central Vietnam is the geographical location of the Wenchang launch site. Hainan Island is situated to the northeast of and not far from Vietnam's central coast.
During the pre-dawn hours, the sky is still dark, but sunlight is beginning to illuminate the upper atmosphere over the eastern horizon. The exhaust plumes and trails created by the rocket at high altitudes catch this sunlight, causing them to become highly reflective and stand out brilliantly against the dark sky.
Explaining the Cone-Shaped Light Phenomenon
Weather experts have clarified that the cone-shaped white trail observed by residents was not smoke or burning fuel. It is a physical phenomenon known as a condensation cloud.
Shockwave: As the rocket travels at hypersonic speeds (much faster than the speed of sound), it generates a shockwave in front of it, compressing the air.
Water Vapor Condensation: This shockwave causes a sudden drop in air pressure and temperature in the region behind the rocket. In humid atmospheric conditions, this abrupt change forces the water vapor in the air to rapidly condense into tiny droplets, forming a visible white cloud.
Mach Cone: This cloud often takes on a distinctive cone shape because the shockwave propagates outward from the nose of the flying object in a cone-like pattern, known as a "Mach cone."
This phenomenon is more easily observed when the rocket passes through humid layers of the atmosphere. It creates a spectacular sight and serves as a clear indicator of the increasing frequency of aerospace activities in the region.
