Why is the background of the astronaut’s exit image dark?
Star rays ‘filtered’ by cameras
Yang Yuguang, vice chairman of the International Astronautical Union Space Transportation Committee, told a reporter from Science and Technology Daily that it was not the “weird disappearance” of these stars that caused this phenomenon, but the result of the “choice” of the camera’s exposure parameters. Stars in photos or videos are “invisible” in deep space.
“The stars are the dimmer subjects in the universe. Conversely, the space station and astronauts are very bright when illuminated by the sun. The camera cannot ‘see’ both bright objects and very dim objects at the same time. How to choose the object? Obviously, during the outboard activities, it is the primary task to clearly capture the details of the astronauts, space station modules and the earth, that is, to set the corresponding camera exposure parameters based on bright objects.” Yang Yuguang said.
Specifically, when the camera locks on the space station and the astronauts who are out of the cabin, because the space station and the astronauts are very bright, the camera must control the amount of light entering and reduce the exposure time in order to capture normal exposure pictures. This low-value adjustment of exposure and aperture inevitably “filters out” the faint glow of stars in space, so the resulting picture is a dark night sky with no stars on it.
If you want to shoot relatively dim stars, the camera needs to increase the amount of light and increase the exposure time. However, this will cause the space station and astronauts in the picture to appear “overexposed” and become white. “The stars in the universe have always been there, it’s just that we artificially ‘ignored’ the stars by adjusting the camera in order to capture the ideal picture of the astronauts exiting the cabin.” Yang Yuguang concluded.
What is the difference between seeing stars in space
The pictures of the astronauts exiting the cabin “filtered” the stars, so can the astronauts in space see the stars? Is it the same as the stars we see on Earth?
Ping Jinsong, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, pointed out that there is no atmospheric scattering in space, and sunlight travels in straight lines, so the entire space will not be illuminated. In dark space, astronauts can see the sky full of stars.
“When an astronaut first steps out of the hatch, if he looks at the earth, his eyes are adapted to bright things, but when he looks up at the dark universe, he may not be able to see the stars for a while. But the human eye is very adaptable, and the eyes adapt to After darkness, you can see the stars.” Yang Yuguang said.
On October 15, 2003, astronaut Yang Liwei took the Shenzhou-5 manned spacecraft and opened the first space gaze of Chinese astronauts. According to his recollection, the moon and stars seen in space were clearer and brighter, and the stars did not “blink”.
On September 27, 2008, astronaut Zhai Zhigang got out of the Shenzhou 7 manned spacecraft, the first time Chinese people “walked in space”. The space in front of him “can’t see the end at a glance”, and he sees “much more stars than on Earth”.
On December 9, 2021, at the “Tiangong Classroom” of the Chinese Space Station, astronaut Wang Yaping revealed that astronauts can see the sunrise 16 times a day because the space station circles the earth every 90 minutes.
“The stars that astronauts see in space are indeed different from what we see on Earth.” Yang Yuguang said that the earth is blocked or interfered by factors such as atmosphere and artificial light sources, making the starlight weaker, and it will also “a Twinkle twinkle,” and fewer stars are visible to the naked eye. In space, because there is no atmospheric barrier or occlusion, the stars viewed by astronauts have three characteristics: less twinkling, clearer and brighter, and more stars.
Ping Jinsong also said that space is a vacuum, and there is no atmospheric turbulence, so the stars will not “blink”, only the stars are scattered, and there are no stars twinkling. Therefore, there will be no halos or halos around stars, planets or the moon, and the stars will be more translucent.