The July night sky

WELCOME TO the July night sky.This month gets off with a ‘bang’, as on July 4, NASA will try to blow a hole in a comet! This attempt is called ‘deep impact’ for obvious reasons.

The science behind the attempt is simple, as up until now no one knows exactly what a comet is made of, and how it would react in such a situation as, for example, a close encounter with the Earth. This is important as comets have in the past, (and will again in the future), posed a threat of collision with the Earth. Also, they are made up of frozen gases that formed at the very beginning of the solar system and may hold clues to the materials involved and the likelihood of other solar systems forming around Sun like stars in our galaxy.

The Deep Impact Probe consists simply of a camera platform and a 350kg mass of solid copper as an impact missile. This mass will hit the comet at the speed of twenty thousand miles per hour and should make a hole the size of a football stadium. The cameras in the probe will image the inside of the comet and relay the data back to Earth. The name of this lucky Comet is Temple One and it orbits the Sun every five and a half years. At the time of the impact, the comet will be in the constellation of Virgo, just one hand’s width to the left of Jupiter from our point of view here on Earth. The actual impact happens during daylight hours in the Algarve, but at nightfall it might be worth having a peak with a small telescope or binoculars just to see if anything is visible – but most astronomers believe the affect will be too small to be easily seen from Earth.

During the first week of July, we have an excellent chance of catching a glimpse of elusive planet Mercury, as this planet is just below and slightly to the left of Venus.

Now Venus is unmistakable in July, shining brightly just above the west northwest horizon. Mercury, in comparison to the brilliant planet Venus, will be seen as a faint pinkish star like object. The crescent Moon will be close to them both on the evening of the 8.

The Moon is new on July 6, first quarter on the 14th, full on the 21st, and last quarter on July 28.

• Clive Jackson is the director of the Astronomical Observatory of Tavira (Sitio do Malhão) and the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach. Tel.: 281 321 754, Fax: 281 324 688, Email: [email protected]. Homepage: