Fluorescent vapour clouds could be visible over Bermuda tonight when a Nasa rocket is launched into orbit – a day later than planned.

The rocket will lift off from a Nasa base in Virginia and release barium vapour while still in the atmosphere.

The green and violet clouds will be visible to the naked eye – but only for about 30 seconds.

The rocket, which at first scheduled to blast off yesterday, is expected to take off about 9pm and will release the cloud of vapour ten minutes into the flight.

A Nasa spokesman said: “Immediately after release of the vapour, the spherical clouds are a mixture of green and violet, but that phase only lasts about 30 seconds when the un-ionised component of the cloud has diffused away.

“After exposure to sunlight the vapour clouds quickly ionise and take on a violet colour.”

The spokesman added that the chemicals were not harmful to the environment or human health.

The rocket is part of Nasa experiments to find out how particles travel through different regions in space that are magnetically connected.