WELCOME TO the January night sky. This month is often clear and cold in Portugal, with more than 14 hours of darkness for night sky watching.
If you feel cold outside at this time, it is good to remember that we are actually closer to the Sun in January than we are in July. This is due to the slightly elliptical orbit of the Earth. In fact, we are five million kilometres closer to the Sun (about three per cent) than in July.
After midnight on the third, there is the peak of the Quadrantid Meteor Shower. This shower is not particularly bright, but at least the sky should be dark as the Moon is not around at this date.
The planet Mars is still dominating the night sky, glowing bright orange high in the south at nightfall. Mars is noticeably less brilliant than it was a few weeks ago, as then it was closer to Earth.
Looking to the east soon after sunset, you should see a bright yellow “star” rising in the constellation of Cancer the Crab. This “star” is, of course, the giant ringed planet Saturn. With a small telescope or strong binoculars, the rings should be visible at this time. The Moon one day past full will be near to Saturn on the night of January 14/15.
In January, Saturn raises approximately at the same time as Sirius, the brightest star in the nighttime sky. Sirius is in the constellation of Canis Major the Big Dog and will flash and sparkle with many different colours when close to the horizon. Saturn, in contrast, will twinkle a lot less and this may help to identify it. Half way between Saturn and Sirius is the bright star Procyon in the constellation of Canis Minor the Little Dog.
The year 2005 was one second longer than 2006. This leap second was added to compensate for the slight slowing down of the Earth’s rotation due primarily to the tidal drag of the Moon. The last time this happened was seven years ago. This is a completely natural effect that has been going on for billions of years.
The Moon is at first quarter on the sixth, full on January 14, last quarter on January 22 and new on January 29.
• Clive Jackson is the director of the Astronomical Observatory of Tavira (Sítio do Malhão) and the Câmera 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], or visit http://www.cdepa.org