Tuesday, October 4, 2022

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Star trails in space captured by NASA astronaut in incredible viral image

An astronaut has wowed the internet by capturing an image he says most space photographers “can only dream of” – star trails from space.

The space photo was taken by Donald Pettit, an active NASA astronaut who has visited the International Space Station (ISS) three times.

Pettit, an avid astrophotographer, used his free time during missions to take photos of space from inside the station’s Cupola, a small glass dome with seven windows that allows astronauts to observe the space and Earth from orbit.

When he last visited the station in 2012, Pettit installed his Nikon D3s camera in the cupola and let it take in all the light possible in a 15-minute shot. The result can be seen below.

The photo is deliberately out of focus because the camera continuously picks up light for 15 minutes, allowing it to capture movement. The white lines at the top of the image are the distant star trails, curved due to the rotation of the space station orbiting Earth.

The lower half of the image shows Earth itself, with orange streaks of city lights and countless blue dots, each a thunderbolt from a thunderstorm below.

Pettit posted the photo, which he calls Lightning Bugs, to Reddit on September 11, 2022. As of September 21, it has earned over 68,000 likes and hundreds of user comments.

talk to PleasemynewsPettit – now back on Earth – discussed the background behind the photo.

“We work 12 to 14 hour days six days a week on the station, and outside of that you’re off duty,” he said. “Outside of your normal working hours, you can do whatever you want, including sleeping, eating and keeping in touch with your family. And then you can spend that time doing photography. If I could do a few hours of photography a day, it would be a real treat.”

A limiting factor is that the conditions are not always good for a photo. The ISS orbits the Earth every 90 minutes. Of that, there are about 30 minutes during which the ISS is in the shadow of our planet, shielded from the glare of the sun.

It’s worth the wait, though. “Stars don’t twinkle because twinkle is an atmospheric phenomenon, and stars are brighter than you’re used to, and they’re more colorful,” Pettit said.

A notable feature of the image is the green glow that separates Earth from space. This is a phenomenon called airglow, and its color can be similar to the twinkling lights in the night sky known as the aurora – the northern and southern lights.

However, airglows and auroras are separate phenomena, driven by different processes.

“Auroras are excited by electrons and other solar particles coming down from Earth’s magnetic fields, which is why you see them in the polar regions,” Pettit said. “Airglow is everywhere on Earth, and molecules in the upper atmosphere are excited by solar activity.”

This causes molecules to collapse to a ground state. An atom is in a ground state when it is at its lowest possible energy as defined by the orbits of its electrons. If an atom enters its ground state from a more excited state, it typically emits a photon of light in the process.

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