NASA astronaut and astrophotographer Donald Pettit just joined Reddit to share some of his photography. Pettit just posted a wonderful star trails image captured during his previous mission to the International Space Station (ISS).
Pettit captured the images on ISS Expedition 30 in 2012. The image, which he calls ‘Lightning Bugs,’ is a 15-minute total exposure created by stacking 1-minute single exposures. Pettit says he used a Nikon D3S at ISO 800. He doesn’t specify the lens used, but he shot at 24mm and F5.6.
Of his image, Pettit says, ‘In the photo, stars make arcing trails in deep space, while a huge thunderstorm pounds Earth below as seen from the time history of lightning flashes. The atmosphere between them glows green with what scientists call airglow, which has a different excitation mechanism than auroras.’
|‘Lighting Bugs’ by Donald Pettit. Click to view the full-size image.|
Airglow is the faint emission of light by a planetary atmosphere. There are quite a few types of airglow above Earth, and they’re visible in the ionosphere and thermosphere. Various processes cause airglow in Earth’s upper atmosphere, including the recombination of atoms photoionized by the Sun during the day, luminescence resulting from cosmic rays hitting the upper atmosphere, and chemiluminescence caused by oxygen and nitrogen reacting with hydroxyl free radicals a few hundred kilometers above Earth. Airglow can affect the performance of ground-based optical telescopes, which is one reason space telescopes like Hubble and Webb can view much fainter objects at visible wavelengths.
As a brief aside, if you want to learn more about the history of Nikon cameras in space, check out this article we published in 2020. You can also learn about Nikon’s storied past by visiting this excellent, detailed history website.
Pettit has also shot a longer star trail image from space. The photo below is a 30-minute capture.