August is usually regarded as “meteor month”, with one of the best meteor displays of the year reaching its peak around mid-month, usually coinciding with the feast of St Lawrence.

This display is of course the annual Perseid Meteor Shower. This year, however, most of the meteors will be drowned by moonlight, coming as it does just three days past full moon.

The peak of the meteor shower is expected to be on the night of 12 – 13 August, when our planet silently drifts through the orbit of comet Swift-Tuttle, encountering debris left in the comet’s wake each time it approaches the sun every 130 years.

This debris rams into the upper atmosphere at speeds of about 60 kilometres per second, causing the air to ionise and shed bright streaks of light as the grain sized particles vaporise. This is what we see as “meteors” or “shooting stars”.

The Perseid shower has been observed for a long time and is known to Maltese folklore as “Dmugh Ta’ San Lawrenz.” The point in the sky – the Radiant – from where these meteors appear to originate lies in the constellation of Perseus, and hence the name of the meteor shower.

Every 12 years, the shower becomes stronger than average. This is due to the effect of the planet Jupiter, which orbits the sun every 12 years, on the meteor stream. The passage of the massive planet pulls the meteoroids closer to the sun, and the core of the stream may be shifted closer to Earth resulting in more meteors being observed. Predictions cannot be accurate, but the normal rate of the meteors from midnight to dawn is 60 per hour. Interference from moonlight this year would drastically reduce this number.

Watching meteors does not require any equipment; only dark skies. Before midnight, when the radiant is still low in the northeast, the meteors enter the upper atmosphere at a low angle and few are visible. As night advances, the radiant rises higher in the sky and meteors arrive nearly straight down, so larger numbers may be observed.

The Astronomical Society Of Malta invites all to join its members and observe this meteor shower from next to the Chapel at L-Ahrax tal-Mellieha from 9.30pm onwards on the night of Saturday 12 –13 August. A computer presentation will also be running continuously from 9.30pm.

The planets Jupiter, Uranus and Neptune are also visible at the time of year and well placed in the sky for observation. Also of interest is the minor planet Ceres, which reaches opposition, that is being opposite the sun in its orbit, on 16 August, making it visible visible almost all night. With a diameter of 933km, Ceres is the largest asteroid in the Solar System. It was discovered by Giovanni Piazzi on 1 January 1801.

Telescopes will also be set up by society members for public viewing of these objects.

Further information about The Astronomical Society Of Malta is available at www.maltastro.org