What was it?
they asked Barbican.

In a few words he explained it.

The beautiful luminous ring was simply an optical illusion, produced by the refraction of the terrestrial atmosphere.

All the stars in the neighborhood of the Earth, and many actually behind it, had their rays refracted, diffused, radiated, and finally converged to a focus by the atmosphere, as if by a double convex lens of gigantic power.
Whilst the travellers were profoundly absorbed in the contemplation of this wondrous sight, a sparkling shower of shooting stars suddenly flashed over the Earth's dark surface, making it for a moment as bright as the external ring.

Hundreds of bolides, catching fire from contact with the atmosphere, streaked the darkness with their luminous trails, overspreading it occasionally with sheets of electric flame.