Sunset, as viewed from Earth orbit
The image was taken by an astronaut, aboard the International Space Station (ISS), orbiting Earth about 350 km high. The ISS was flying over central South America.
Credit: NASA/JSC Gateway to Astronaut Photography of Earth
NASA recently published a beautiful image, showing sunset, as observed from Earth orbit. The image was taken by an astronaut, onboard the International Space Station (ISS), orbiting about 350 km above Earth’s surface. The ISS, Earth’s largest artificial satellite, is 109 m across, and weighs over 400,000 kg. It serves as an orbital manned observatory, from which astronauts can monitor our dynamic planet, and explore the entire cosmos.
Since the ISS orbits Earth every 91 minutes, it completes about 16 revolutions around Earth, every day. Therefore, the astronauts of the ISS see about 16 sunrises and sunsets, every 24 hours. They can also observe the terminator, a zone on Earth's surface, separating the day side from the night side.
The terminator is not a sharp edge between light and darkness, as light fades gradually, across the terminator, due to the scattering of light by the Earth’s atmosphere. On the surface of Earth, this zone of diffuse illumination is experienced as twilight.
In the above image, the terminator is visible across central South America. The tops of clouds have reddish hues, due to direct light from the setting Sun. Earth’s atmosphere, visible on the horizon (Earth’s limb), varies from bright white to deep blue.
References
Sunset over Western South America
http://earthobservatory.nasa.gov/IOTD/view.php?id=50205
NASA’s ISS Webpage
http://www.nasa.gov/mission_pages/station/main/
Wikipedia