The Largest Nuclear Test in Outer Space Had Startling Effects on Hawaii

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A little more than fifty-seven years ago, on July 8, 1962, a bright new "sun" dawned in the nighttime sky over Hawaii. Briefly resembling the blazing sphere of nuclear fusion that is our bright sun, this fiery burst quickly ballooned to seem as if it would consume the sky itself. It was a thermonuclear blast, 250 miles up, triggered by a 1.4 megaton fusion bomb called Starfish Prime. To date, it remains the largest nuclear test ever conducted in outer space.

Photograph of the Starfish Prime high-altitude nuclear test explosion.

U.S. government personnel with the Atomic Energy Commission and the Defense Atomic Support Agency carried out the experiment, witnessed by thousands of Americans on the Hawaiian Islands. Though Starfish Prime detonated roughly 900 miles away, the initial spherical explosion could be viewed quite clearly from the ground. The sky then lit up with artificial auroras, a result of some of the 10^29 energetic electrons released from the blast reaching and being absorbed by the atoms and molecules of Earth's mesophere. These could be seen as far away as New Zealand.  For roughly seven minutes, the night was a glorious light show, "like turning on all the lights over the Hawaiian Islands for a super-super athletic contest," the Honolulu Advertiser reported. Afterwards, the sky gradually dimmed to an eerie glow which persisted for four hours.

Starfish Prime's effects were also felt on the ground. The blast triggered an electromagnetic pulse (EMP), a result of electrons being rapidly accelerated and fleetingly forming their own powerful magnetic field. Citizens reported that almost at the very instant of the blast, radios blacked out, telephones stopped working, and thirty strings of streetlights on the island of Oahu spectacularly failed.

Higher up, Starfish Prime's effects lingered for months. Extra energetic electrons trapped by Earth's magnetic field formed their own radiation belts which damaged the internal components of various orbiting satellites. At least six were rendered inoperable over time, including Telstar 1, the first satellite to relay television pictures and telephone calls through space.

Only a few more nuclear tests in space were performed in the wake of Starfish Prime, and none came remotely close to its daunting power. The Partial Test Ban Treaty would enter into effect the following year, ending all above ground nuclear tests.

It's a good thing we haven't seen another nuclear test in space since. Subsequent analyses suggest that any detonation in low-Earth orbit would be extremely hazardous to the 1,400+ satellites and six astronauts currently inhabiting in the region.

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