October 20, 2018
Today and every Saturday Earth Science Picture of the Day invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.
The photo above shows Comet PanSTARRS juxtaposed with a coral-colored jet contrail as observed from Valley Forge, Pennsylvania, at sunset on March 14, 2013. The contrail's red color gives testimony to the fact that the Sun was close to the horizon. Note that the comet tail scatters all wavelengths of white light, so it'll appear reddish only after passing through our atmosphere. Thus, the color of the comet could be different if observed from other positions; the contrail is reddish from all perspectives. Strong winds were quickly dispersing the contrail -- see the eddies, at the top.
PanSTARRS is an abbreviation for Panoramic Survey Telescope and Rapid Response System. Comets are named after the person or persons who discovered them, but in this case, a team of scientists using the PanSTARRS telescope system made the discovery (in June 2011), so it was decided to name it after the instrument instead.
The comet’s nearest approach brought it within about 100 million mi (160 million km) of Earth – on March 10. PanSTARRS is a non-periodic comet -- it's never passed this way before. Look for it tonight and this weekend to the right (north) of the setting Sun about an hour after sunset, but you’ll likely need binoculars to spot it.
At right is a glimpse of the very thin crescent Moon, earthshine and Comet PanSTARRS (at far left). I took this photo earlier this month, with Kevin Richardson’s help, at Eagle Creek Airpark, Indiana. See the Related Links (below) for other views of Comet PanSTARRS.
Photo Details: I captured the featured shot using a 75mm to 300mm lens; attached to a Modified Canon Rebel Xsi camera; 80mm Refractor/Modified Canon 40D; 0.5 second exposure.
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