By CLIVE JACKSON
WELCOME TO the July night sky. This month begins with the giant planet, Jupiter, with a volume 1,300 times larger than our Earth, visible high in the south at sunset. On the night of July 5, the Moon was below Jupiter, in the constellation of Libra. Through a small telescope or even just binoculars, Jupiter is a fine sight, with its four major moons easily visible.
The surface of this planet is not solid but gaseous, covered in colourful cloud belts, representing weather patterns high in the atmosphere of Jupiter. The winds in these cloud belts can exceed 400kph, and storm systems can last for decades in this turbulent atmosphere. Jupiter really is a giant planet.
Low in the west, just after sunset, the planets Saturn and Mars are rapidly disappearing in the evening twilight. On July 27, the very thin crescent Moon will be just above Mars.
Low in the south during July, the zodiacal constellation of Scorpius is easily seen, with the bright star, Antares, glowing red, just about a hand’s width to the left of Jupiter. Antares is a super giant star, more than one million times the volume of our Sun. The Moon will be in Scorpius on July 7.
Just to the left of Scorpius, we have the constellation of Sagittarius. The summer Milky Way passes through this area, and the centre of our galaxy is contained in this wonderful star field. Right overhead, in July, is the brilliant white star Vega. This star is one of our closest neighbours, 26 light years away, in the constellation of Lyra.
Our Earth was at the aphelion point of its orbit on July 3, which means that it is at its furthest away from the Sun at this time. The difference is slight and will not make our summers noticeably cooler.
The Moon is at First Quarter on July 3, Full on July 11, Last Quarter on July 17 and New on July 25.
• Clive Jackson is the director of the Astronomical Observatory of Tavira (Sítio 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, e-mail [email protected] – visit www.cdepa.pt