Submitted by Dr. Andrew Resnick
This week’s science photo features an image of the comet NEOWISE showing both the ion and dust tails. C/2020 F3 (NEOWISE) or Comet NEOWISE is a retrograde comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers using the NEOWISE space telescope. At that time, it was a 10th-magnitude comet, located 2 AU away from the Sun and 1.7 AU away from Earth. As a comet approaches the inner Solar System, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus, carrying dust away with them. Separate tails are formed of dust and gases, becoming visible through different phenomena; the dust reflects sunlight directly and the gases glow from ionisation. [from Wikipedia].
This image was created by “stacking” 248 individual images, a process that averages together many images to reduce noise. Individual images were first acquired around 10:30 pm on July 17, 2020. The camera and lens settings for each image were 3sec exposure using a 105mm f/1.4 lens, ISO varying between ISO 64 and ISO 800. The stacking process introduces some artifacts- the comet moves with respect to the stars, so stacking the frames to align the stars results in the comet being ‘dragged’ across the frame.
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