Scotland’s Sky in January, 2017

Moon between Venus and Mars on the 2nd

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st. Arrows depict the motions of Mars during the month and of Venus from the 12th. (Click on map to enlarge)

The new year opens with the Moon as a slim crescent in our evening sky, its light insufficient to hinder observations of the Quadrantids meteor shower.

Lasting from the 1^st to the 6^th, the shower is due to reach its maximum at about 15:00 GMT on the 3^rd. Perhaps because of the cold weather, or a lingering hangover from Hogmanay, this may be the least appreciated of the year’s top three showers. It can, though, yield more than 80 meteors per hour under the best conditions, with some blue and yellow and all of medium speed. It can also produce some spectacular events – I still recall a Quadrantids fireball many years ago that flared to magnitude -8, many times brighter than Venus.

Although Quadrantids appear in all parts of the sky, perspective means that their paths stream away from a radiant point in northern Bootes. Plotted on our north map, this glides from left to right low across our northern sky during the evening and trails the Plough as it climbs through the north-east later in the night. The shower’s peak is quite narrow so the optimum times for meteor-spotting are before dawn on the 3^rd, when the radiant stands high in the east, and during the evening of that day when Quadrantids may follow long trails from north to south across our sky.

Mars and Venus continue as evening objects, improving in altitude in our south-south-western sky at nightfall and, in the case of Venus, becoming still more spectacular as it brightens from magnitude -4.3 to -4.6. Mars, more than one hundred times fainter, dims from magnitude 0.9 to 1.1 but is obvious above and to Venus’ left, their separation falling from 12° to 5° during the month as they track eastwards and northwards from Aquarius to Pisces.

On the evening of the 1^st, Mars stands only 18 arcminutes, just over half a Moon’s breadth, above-left of the farthest planet Neptune though, since the latter shines at magnitude 7.9, we will need binoculars if not a telescope to glimpse it. At the time, Neptune, 4,556 million km away, is a mere 2.2 arcseconds wide if viewed telescopically and Mars appears 5.7 arcseconds across from a range of 246 million km. On that evening, the young Moon lies 8° below and right of Venus, while on the 2^nd the Moon stands directly between Mars and Venus. The pair lie close to the Moon again on the 31st.

As its distance falls from 115 million to 81 million km this month, Venus swells from 22 to 31 arcseconds in diameter and its disk changes from 56% to 40% sunlit. In theory, dichotomy, the moment when it is 50% illuminated like the Moon at first quarter, occurs on the 14^th. However, the way sunlight scatters in its dazzling clouds means that Venus usually appears to reach this state a few days early when it is an evening star – a phenomenon Sir Patrick Moore named the Schröter effect after the German astronomer who first reported it. Venus stands at its furthest to the east of the Sun, 47°, on the 12^th.

The Sun climbs 6° northwards during January and stands closer to the Earth in early January than at any other time of the year. At the Earth’s perihelion at 14:00 GMT on the 4^th the two are 147,100,998 km apart, almost 5 million km less than at aphelion on 3 July. Obviously, it is not the Sun’s distance that dictates our seasons, but rather the Earth’s axial tilt away from the Sun during winter and towards it in summer.

Sunrise/sunset times for Edinburgh change from 08:43/15:49 on the 1^st to 08:09/16:44 on the 31^st. The Moon is at first quarter on the 5^th, full on the 12^th, at last quarter on the 19^th and new on the 28^th.

The Moon lies below the Pleiades on the evening of the 8^th and to the left of Aldebaran in Taurus on the next night. Below and left of Aldebaran is the magnificent constellation of Orion with the bright red supergiant star Betelgeuse at his shoulder. Soon in astronomical terms, but perhaps not for 100,000 years, Betelgeuse will disintegrate in a supernova explosion.

The relics of a supernova witnessed by Chinese observers in AD 1054 lies 15° further north and just 1.1° north-west of Zeta Tauri, the star at the tip of Taurus’ southern horn. The 8^th magnitude oval smudge we call the Crab Nebula contains a pulsar, a 20km wide neutron star that spins 30 times each second.

The conspicuous planet in our morning sky is Jupiter which rises at Edinburgh’s eastern horizon at 01:27 on the 1^st and at 23:37 on the 31^st. Creeping eastwards 4° north of Spica in Virgo, it brightens from magnitude -1.9 to -2.1 and is unmistakable in the lower half of our southern sky before dawn. Catch it just below the Moon on the 19^th when a telescope shows its cloud-banded disk to be 37 arcseconds broad at a distance of 786 million km. We need just decent binoculars to check out the changing positions of its four main moons.

Saturn, respectable at magnitude 0.5, stands low in our south-east before dawn, its altitude one hour before sunrise improving from 3° to 8° during the month. Look to its left and slightly down from the 6^th onwards to glimpse Mercury. This reaches 24° west of the Sun on the 19^th and brightens from magnitude 0.9 on the 6^th to -0.2 on the 24^th when the waning earthlit Moon stands 3° above Saturn.

Alan Pickup