Earth by night a spectral delight

A view of the Milky Way from the International Space Station. Photo / NASA
A view of the Milky Way from the International Space Station. Photo / NASA

Astronauts aboard the International Space Station (ISS) see the world at night on every orbit - that's 16 times each crew day. An astronaut took this broad, short-lens photograph of Earth's night lights while looking out over the remote reaches of the central equatorial Pacific Ocean. At the time, ISS was passing over the island nation of Kiribati, about 2600km south of Hawaii.

Knowing the exact time and the location of the ISS, scientists were able to match the star field in the photo to charts describing which stars should have been visible at that moment. They identified the pattern of stars in the photo as our Milky Way galaxy (looking towards its centre). The dark patches are dense dust clouds in an inner spiral arm of our galaxy; such clouds can block our view of stars towards the centre.

The curvature of the Earth crosses the centre of the image and is illuminated by a variety of airglow layers in orange, green and red. Setting stars are visible even through the dense orange-green airglow.

The brightest light in the image is a lightning flash that illuminated a large mass of clouds.

The flash reflected off the shiny solar arrays of the ISS and back to the camera. The dim equatorial cloud sheet is so extensive that it covers most of the sea surface in this view.

Astronaut photograph ISS044-E-45215 was acquired on August 9, 2015, by a member of the Expedition 44 crew, with a Nikon D4 digital camera using a 28mm lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Centre, Houston.

- NZ Herald

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