Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2021 August 10
The picture shows a glowing soot in a spherical flame in the
microgravity of space. 
Please see the explanation for more detailed information.

Fire in Space
Image Credit: NASA

Explanation: What does fire look like in space? In the gravity on Earth, heated air rises and expands, causing flames to be teardrop shaped. In the microgravity of the air-filled International Space Station (ISS), however, flames are spheres. Fire is the rapid acquisition of oxygen, and space flames meet new oxygen molecules when they float by randomly from all directions -- creating the enveloping sphere. In the featured image taken in the ISS's Combustion Integration Rack, a spherical flame envelopes clusters of hot glowing soot. Without oxygen, say in the vacuum of empty space, a fire would go out immediately. The many chemical reactions involved with fire are complex, and testing them in microgravity is helping humanity not only to better understand fire -- but how to put out fire, too.

Tomorrow's picture: bubble cloud row


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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