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Our Electric Earth at Night: the “Black Marble”

Suomi NPP composite satellite image of North and South America at night

Suomi NPP satellite image of North and South America at night

In daylight our big blue marble is all land, oceans and clouds. But the night is electric.

This image of North and South America at night is a composite assembled from data acquired by the Suomi NPP satellite in April and October 2012. The new data was mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet.

The nighttime view was made possible by the new satellite’s “day-night band” of the Visible Infrared Imaging Radiometer Suite. VIIRS detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires, and reflected moonlight. In this case, auroras, fires, and other stray light have been removed to emphasize the city lights.

Although the view looking down from space is of a sparkling show, the downside of course is light pollution over major metropolitan areas which impede the view of the night sky from the ground. (Find out more at the International Dark Sky Association site.)

Read more (and watch a video of these nighttime images of Earth) below:

Read the rest of this entry

The Town That Billy Sunday Couldn’t Shut Down

Expedition 30 photo of Chicago on the night of Feb. 2, 2012. (NASA)

Here’s a view from the ISS, looking down at the brightly-lit Chicago metropolitan area on February 2, 2012. Lake Michigan is the dark expanse seen below the clouds — perhaps a dense fog bank — at bottom center.

According to NASA, fog is not common in the Great Lakes area this time of the year as it’s usually too windy (the “Windy City”!) but this has been an exceptionally mild winter. The faint gold line of airglow — caused by ultraviolet radiation from the Sun exciting gas molecules in the upper atmosphere — can be seen just above the horizon. Minor auroral activity is visible in upper right.

And since we’re here, heres some fun facts about Chicago:  Read the rest of this entry


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