Mars, Jupiter, Uranus, Venus, Neptune, Mercury and Saturn will be visible together in the UK during a brief window between sunset and around 1830 GMT.

Even though the planets are separated by huge distances in space and orbit the Sun at different speeds, there are moments when they appear to align from Earth's perspective.

Mercury has now joined the six other planets already in formation, and experts say the best chance of seeing all seven in the UK is from Tuesday to Friday.

The heavenly show has already been dazzling spectators around the world, from Mexico to Japan, though with different timings.

The UK is holding events across the country to celebrate the parade, including astronomer-led tours in a Welsh national park and open evenings at an observatory in the Scottish city of Dundee.

If Britain's notoriously fickle weather brings clear skies at the right time, Venus, Mars and Jupiter will be the easiest to see, astronomy education officer Jessica Lee, of London's Royal Greenwich Observatory, explained.

"They can be spotted with just your eyes, even from a place like London. Venus, the evening star, is really bright, while Mars is high in the southern sky, between the constellations of Orion and Gemini and Jupiter is also high in the south."

But stargazers will not be able to make out the full lineup with the naked eye.

"Uranus is really close to Jupiter but is so faint that most people would need a telescope," Lee said.

"Saturn is just above the horizon as the Sun is setting, so you might be able to see it if you have a clear view of the western horizon.

"You'll have to have a telescope to see Neptune but Mercury is just visible where the Sun is setting for a short period of time."