<preform>Stars & Planets: August</preform>

Mars is making a once-in-a-lifetime spectacular appearance

This month, Britain's stargazers will be opening up their observatories and telescopes to let everyone have a glimpse of what's really up there in the cosmos - 23-30 August is National Astronomy Week.

This month, Britain's stargazers will be opening up their observatories and telescopes to let everyone have a glimpse of what's really up there in the cosmos - 23-30 August is National Astronomy Week.

These days, every week is "national something week". But Britain's astronomers have always strived to be more focused. National Astronomy Week is not an annual event; it occurs every four or five years when there's something special to see.

It started in 1981, which was the 200th anniversary of the first discovery of a new planet. Musician and amateur astronomer William Herschel found the new world from outside his home in Bath in March 1781. Ever mindful of the importance of royal flattery, he wanted to name the planet after the king - but European astronomers thought a roll-call of planets ending Jupiter, Saturn, George didn't sound right, so it became Uranus.

In November 1985, Britain's astronomers homed in on Halley's Comet. Given how dim the comet appeared, as seen from northern latitudes, the best view most people had was through the telescope of a local observatory during National Astronomy Week. At one observatory on the South Downs, 100 people queued to see the "comet of a lifetime" on one frosty evening.

The National Astronomy Week in 1990 raised the problem of light pollution. It brought the subject of polluting the sky with light into public discussion.

In August 1999, another rare astronomical sight was the focus for National Astronomy Week - the first total eclipse of the sun for more than 70 years.

Now it's the turn of Mars. The Red Planet is putting on its finest show since Neanderthal times. It's opposite to the sun in the sky on 28 August, but because the planet has an oval-shaped orbit, it's closest to the Earth the previous day. National Astronomy Week is celebrating not just this historic event, but Britain's Beagle 2 spaceprobe, now on its way to the Red Planet for a landing on Christmas Day.

Wherever you are in the country, there's an observatory somewhere nearby that will be opening to show Mars at its best. And there'll be presentations where you'll have the chance to listen to Britain's top planetary scientists.

Off the Mars-circuit, there'll be exhibitions and talks on the Sun, the Big Bang, the history of astronomy. The Observatory Science Centre at Herstmonceux in Sussex, is holding a whole week of activities and competitions for children. And the West of London Astronomical Society promises several nights to remember at the Ruislip Lido, including a "Starlight Express" ride through a vast model solar system.

www.astronomyweek.org.uk

What's Up

"Star" of the month is of course the planet Mars, making its historic close approach to Earth. Currently it's shining far brighter than any of the stars. In fact, Mars is the brightest object you'll see in the night sky, after the Moon.

On the downside, Mars isn't that high in the sky. If you have tall buildings or trees to the south, you may not be able to see it at all. So do make an effort to find somewhere with a good southern view to see this once-in-history appearance.

High above Mars, look out for the Summer Triangle. It's marked by three bright stars, set well apart in the sky. The lower apex is Altair, the most prominent member of the constellation Aquila (the eagle). To the upper right is brilliant Vega, in the otherwise faint star-pattern of Lyra (the lyre).

And the third corner is marked by Deneb, to the upper left. It's the main star of Cygnus (the swan), a large cross-shaped constellation. To the ancient Greeks, this was a flying swan, with its brightest star denoting its tail. The name Deneb is Arabic, and means "tail".

To the lower right, the bottom star of the cross - Albireo - marks the swan's head. The Arabs called it Al Minhar, appropriately denoting "the beak". The star's current name is meaningless, and seems to be the result of mistakes in copying down the years. Regardless of its name, Albireo is one of the loveliest sky sights when seen through a small telescope. It's actually a close double star, with one star yellow-gold and the other blue.