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Catching the elusive gegenschein

The gegenschein, or counterglow, is a faint brightening of the night sky in the region opposite the sun. It’s sunlight scattered by interplanetary dust.

Image via Jeff Dai.

The gegenschein in the whitish blur toward the top of this photo by Jeff Dai. The prominent loop and colors near the horizon are airglow.

Jeff Dai captured this photo in early October, 2016 at Lake Puma Yumco, Tibet, China. He wrote:

Have you ever seen the gegenschein? There’s no doubt it’s one of the greatest night sky naked-eye challenges, a rarely discernable faint glow that can be seen 180 degrees from the sun [for example, overhead at midnight] in an extremely dark sky.

Like the zodiacal light, the gegenschein is sunlight scattered by interplanetary dust. Most of this dust is orbiting the sun in about the ecliptic plane, with a possible concentration of particles at the L2 Earth–sun Lagrangian point.

Pictured above, this single, tracked photo recorded the gegenschein in constellation Pisces over Lake Puma Yumco, Tibet, China early this month. October–November are the peak viewing season to observe gegenschein.

Are you up for the challenge?

Thank you, Jeff! Read more about the gegenschein, or counterglow, from Atmospheric Optics.

By the way, Jeff also pointed out that you can also see airglow in this photo, above the horizon. The prominent loop is airglow, its special structure due to gravity waves.

Also interesting is the star Achernar, a far-southern star that Northern Hemisphere skywatchers rarely see. It is toward the bottom center of the photo, peeking just above the high Himalayan peak Gulha Kangri.

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Deborah Byrd

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