A dazzling night out with Hale-Bopp

David Lister takes his seat on a flight full of enthusiasts in pursuit of the comet

A latecomer rushed breathlessly into the boarding lounge at Manchester airport: "Is this the flight to the comet?" It was. And the crowds at the next gate, leaving for Malaga, began to eat their hearts out.

Almost 200 of us were on the flight which left Manchester on Saturday night, was two hours long, and specified on the tickets Departure Manchester; Destination Manchester.

In simple terms it cost pounds 125 to go 37,000ft up on a Boeing 757, fly across Ireland and over the Atlantic, turn round and come back. But this was not a night for such a prosaic summary.

Here was a new form of space exploration, a seven-mile-high astronomy lesson with the stars a visual aid, a chance to commune with the universe; with a visit to the cockpit and a free bottle of plonk thrown in.

Two enterprising British Airways pilots, running their own company Aviatour, decided to take up two flights, one from London, one from Manchester, to show amateur astronomers, enthusiasts, and some who candidly admitted that there was not much on the television that night, to see the comet Hale-Bopp from an aircraft well above the light pollution, which makes observation of the night sky such a gamble on land.

Both flights were sold out. The London flight had as its communicator the television astronomer Patrick Moore; the Manchester journey had Dr John Mason, vice president of the British Astronomical Association, and knowledgeable, excitable and gesticulation-prone enough to be a Patrick Moore in the making.

Before we boarded, Dr Mason gave us all an illustrated talk about comets. Astronomers have little small talk. It is hard to discuss football and sex scandals when your business is galaxies and dust tails. So most of the audience sat staring intently into the middle distance until he appeared in the airport conference room, then listened with equal intensity.

It was astonishing stuff, fascinating that this comet had given such joy to astronomers that Dr Mason literally and unintentionally jumped, yes jumped, in the air while describing how we would see both its dust tail and gas tail from the aircraft: one could not do this from the ground. Even a simple instruction such as "no photography on the plane chaps" was couched in terms of time and space.

"There is no point using flash," he told us animatedly, "it will take eleven-and-a-half minutes for the light to reach the comet, and eleven- and-a-half minutes to be reflected back to you, by which time the plane will have moved on."

On board, Captain Peter Hughes delighted the aircraft enthusiasts by inviting us up in small groups to see the cockpit and view the comet from there, although it was hard for non- astronomers to know whether to be more excited about Hale-Bopp than about a full-frontal view of the coast of Wales.

In the cabin, the passengers got friendly: impossible not to when every 10 minutes you swap seats with your neighbours so that you all get a view out of the window, sharing your binoculars, with the cabin lights turned off for the whole flight so that for once you can really see the night sky out of an aircraft window.

The comet was distinctly visible, as were its gas and dust tail, but actually as exciting was Mars, shining pink, its big-brother light intimidating its neighbours. Indeed, the whole Milky Way was spread out on view and was described by Dr Mason on the public- address system. I was tempted to think, forget the comet, why are there not aircraft flights simply to view the stars on a regular basis; would it be more interesting than a film on a normal night flight?

And then a tremor went through the aircraft. A muttering, a shuddering, a frisson of excitement. The aurora borealis - the northern lights to you and me - lit up the sky, an unanticipated climax to show off Hale-Bopp to its best effect.

Dr Mason could not contain himself. "The northern lights," he all but shrieked. "We weren't expecting this, we were not expecting this!"

Disembarking, the chat, like the experience, was other-worldly. For one traveller, Alex Smith, from Manchester, who had always wanted to go into astronomy - "but there were more jobs in construction" - it was a dream come true.

"The comet is just a focal point," he said. "To have the universe as a backdrop is mind boggling. It's nature on the grandest scale, and it filled me with awe. It gives you a spiritual sense, makes you wonder about God. And you can't put a price on that."

Cosmic snowball that will fade from view soon

Comet Hale-Bopp will look be in our skies for a few weeks more before disappearing from view in mid May. It is one of the brighter comets of the last 500 years. Good views can be had in early April, free from interference by the moon. It will be easily seen in the north-western sky one hour after sunset. Binoculars will show its two tails best, one yellow the other bluish. After May it will not return until the 54th century.

A comet consists of ices such as water, carbon-dioxide, methane and rocky material, which boil off into vapour and dust as the comet draws near to the sun.

Radiation pressure from the sunlight pushes some of the dust away from the sun creating a long, curved yellow tail. The solar wind also blows the gases into a straight bluish plume.