Astronaut Liu Boming works outside the Tianhe core module Sunday, with a view of Earth in the background. Photo: VCG

The opened exit of the Tianhe core module. Photo: VCG

Astronaut Liu Boming mounts a foot restraint on the robotic arm of the Tiangong space station. Photo: VCG

Astronaut Tang Hongbo prepares to exit the Tianhe core module on Sunday. Photo: VCG

Astronaut Tang Hongbo is tethered to the handrails while working outside the space station. Photo: VCG

Astronaut Tang Hongbo mounts equipment on the robotic arm on Sunday. Photo: VCG

Astronauts work to lift the panoramic camera outside the space station on Sunday. Photo: VCG

Astronaut Nie Haisheng collaborates with Tang Hongbo and Liu Boming from inside the Tianhe core module on Sunday. Photo: VCG