In 1962, the US detonated a 1.4-megaton nuclear warhead 400km above the Pacific, creating artificial auroras visible from Hawaii, knocking out streetlights in Honolulu, and accidentally inventing electromagnetic pulse warfare.
U.S. Air Force 1352nd Photographic Group, Lookout Mountain Station, Public domain, via Wikimedia Commons
A Star Is Born
At 11:00 PM local time on July 9, 1962, the sky over the Pacific Ocean tore open. A Thor missile, launched from Johnston Atoll, had carried a W49 thermonuclear warhead 400 kilometers (250 miles) into the upper atmosphere and detonated it. The test, codenamed Starfish Prime, had a yield of 1.4 megatons, roughly 100 times more powerful than the bomb dropped on Hiroshima. For several minutes, a blood-red and pink aurora stretched across the sky, visible from Hawaii to New Zealand. Some hotels in Hawaii even held "rainbow bomb" parties on their rooftops to watch the display.
The test was part of Operation Fishbowl, a series designed to study the effects of nuclear weapons in the exo-atmosphere. Earlier high-altitude tests in 1958 had produced unexpected results, and scientists wanted to gather more data on the potential military applications, particularly for anti-ballistic missile systems. The explosion released an estimated 10^29 high-energy electrons that interacted with the Earth's magnetic field, creating the visual effects. But these electrons also produced consequences that scientists had not fully anticipated.
The Pulse and the Poisoned Belts
Almost 1,450 kilometers (900 miles) away in Hawaii, the detonation's effects were felt instantly. A powerful electromagnetic pulse (EMP)—far larger than predicted—surged through the islands. It knocked out about 300 streetlights in Honolulu, triggered countless burglar alarms, and damaged a microwave telephone link, cutting off communication from Kauai to the other islands. Many of the instruments designed to measure the EMP were driven completely off-scale.
A more lasting problem developed in the orbits above. The detonation injected a massive number of charged particles into the Earth's magnetosphere, creating a powerful radiation belt. This man-made extension of the Van Allen belts was far more intense and persistent than expected, with some electrons remaining trapped for over five years. This radiation proved fatal for the nascent satellite infrastructure of the era. Within months, at least seven satellites failed, including the United Kingdom's first satellite, Ariel 1, and the AT&T telecommunications satellite, Telstar 1, which was launched just one day after the test. The test effectively disabled a third of all satellites in low-earth orbit at the time. The unexpected and far-reaching consequences of Starfish Prime led to the Partial Test Ban Treaty of 1963, which prohibited nuclear detonations in the atmosphere, in space, and underwater.
💡Fun Facts
The first attempt at the Starfish Prime test, on June 20, 1962, ended in failure when the Thor missile's engine cut out after 59 seconds. The rocket was destroyed by the range safety officer, scattering radioactive debris over Johnston Atoll.
The artificial aurora created by the blast was unusually bright and long-lasting, with some colorful glows remaining visible for over seven minutes.
The EMP was so much stronger than anticipated that many scientific instruments intended to measure it were immediately knocked offline or had their readings go off the scale.
The radiation belt created by Starfish Prime was so intense it damaged Telstar 1, the world's first commercial communications satellite, which had been launched by AT&T the very next day.
