U.S. and UK secretly tested a nuclear missile at night over Puerto Rico

Footage posted on social media showed a bright object streaking across the night sky at about 23:25 UTC, the Caribbean Astronomical Society said, calling it a “military test” but not identifying the country responsible.

Analysts said the launch likely involved a UGM-133 Trident II D5 submarine-launched ballistic missile fired from either a U.S. Navy or Royal Navy submarine, carrying an unusual payload — possibly a hypersonic glide vehicle. There has been no official confirmation from Washington or London.

The Trident II D5 is the backbone of the U.S. and U.K. sea-based nuclear deterrent. The missile is deployed on 14 U.S. Ohio-class submarines (each carrying up to 20 missiles) and four British Vanguard-class submarines (each carrying up to 16). Its range is about 7,360 kilometers. The three-stage, solid-fuel missile can carry up to 12 independently targeted warheads.

The missile weighs about 58,500 kilograms, is 13.4 meters long and 2.1 meters in diameter. It is built by Lockheed Martin and is regarded as one of the most accurate and reliable sea-based strategic deterrent systems in the world.

The U.S. has already begun a modernization program to keep the Trident II effective into the 2080s. In January, Lockheed Martin won a $383 million contract to develop the D5LE2 life-extension program, which will equip the new Columbia-class submarines. Britain’s forthcoming Dreadnought-class submarines, due to replace the Vanguard boats in the early 2030s, will also carry upgraded missiles.

Officials in both countries stress that updating sea-based deterrent systems is critical as potential adversaries develop new missile-defense and anti-ship capabilities. The lack of comment following the Sept. 21 launch, however, leaves open key questions: whether the flight was the first test of a Trident II modified to carry a hypersonic vehicle, or a classified routine trial.