Venus and Orion dominate our January evenings

Alan Pickup

Author: Alan Pickup
The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st.

Our chill January evenings bring the spectacular sight of Orion at the centerpiece in an array of bright stars and constellations. The annual Quadrantids meteor shower should also enliven the next few nights, but, with the conspicuous exception of Venus, the brighter planets are taking an extended New Year holiday.

Venus, brilliant as always, improves from magnitude -4.0 to -4.1 while its altitude in Edinburgh’s south-south-western sky at sunset climbs from 15° to 26° and by the month’s end it sets in the west four hours after sunset. It lies in the middle of Capricornus as the year begins but speeds east-north-eastwards and onwards through Aquarius where it makes an impressive sight 5° above-right of the young earthlit Moon on the 28th. Telescopes show its dazzling gibbous disk which swells from 13 to 15 arcseconds as its distance, still on the far side of its orbit, shrinks from 191 million to 163 million km.

Quadrantid meteors are already arriving but the shower builds to quite a sharp peak on the 4th. Perspective means that they appear to diverge from a radiant point which lies low in our northern sky (see chart) during the evening and trails below and left of the Plough’s handle as it climbs high into the east during the morning hours. Under prefect skies before dawn on the 4th a lucky observer might spot 80 or more medium-speed Quadrantids per hour, with many of the brighter ones leaving persistent glowing trains in their wake.

Orion rises in the east as darkness falls and lies below and left of Taurus as it climbs through our south-eastern sky to cross the meridian at 23:00 GMT on the 1st and by 21:00 on the 31st.

After our focus on Taurus last month, it is time to turn to Orion, which, since it straddles the sky’s equator and forms such a distinctive pattern, is recognised in cultures worldwide. Its earliest representation appears to have been carved into a piece of mammoth ivory more than 32,000 years ago.

The Orion we know makes his appearance in Greek mythology as an all-powerful hunter. In one myth, he fell in love with the Pleiades and is pursuing them across the sky while many stories tell of his death from a scorpion’s sting – said to be the reason that the constellation of the scorpion, Scorpius, is set opposite Orion in the sky.

A line through the three stars of Orion’s famous Belt slants up towards Aldebaran and down to Sirius in Canis Major, the larger of the Orion’s two faithful hunting dogs. The other is Procyon in Canis Minor which, together with Sirius and the red supergiant star Betelgeuse at Orion’s shoulder, form the nearly-equilateral triangle we call the Winter Triangle.

Betelgeuse, perhaps 700 light years (ly) away, is some 15-20 times more massive than our Sun but 800 times wider with a surface at 3,300°C, much cooler and redder than the Sun’s 5,500°C. Although it formed only around 8 million years ago, the star is already exhausting the hydrogen and helium nuclear fuel near its core and is predicted to explode as a supernova within the next million years. It pulsates slowly and erratically in size and brightness over the months and has occasionally outshone the contrasting blue supergiant star Rigel at Orion’s knee. Recent weeks, though, have seen Betelgeuse fade to magnitude 1.2, less than half as bright as Rigel and a level not seen in fifty years.

Rigel, thought to lie about 950 ly away and be slightly more massive than Betelgeuse, is one tenth as wide with a surface at a blistering 12,000°C. Like most of Orion’s other bright stars, it, too, is approaching its end in a supernova.

Don’t miss the chance to spot the Orion Nebula which appears as a fuzzy cloud in Orion’s Sword, a line of relatively dim stars that hang below the Belt. This region, 1,350 ly away, is a cloud of gas and dust in which new stars and planets are forming. If light pollution stops us seeing it with the unaided eye, then binoculars make it obvious.

Sunrise/sunset times for Edinburgh change from 08:44/15:49 on the 1st to 08:10/16:43 on the 31st. The Moon is at first quarter on the 3rd and full on the 10th when it moves through the northern region of the Earth’s shadow, the penumbra, in the first of four penumbral lunar eclipses in 2020. We see very little of the other three, but this one is visible in its entirety between 17:08 and 21:12 as the full moon climbs through our eastern sky. The Moon’s southern part should dim noticeably around mid-eclipse but it doesn’t stray into the central dark umbra of the shadow. Last quarter occurs on the 17th and the Moon is new on the 24th.

Jupiter, bright at magnitude -1.9, begins to emerge from our morning twilight later in the month and lies 10° below-left of the waning Moon on the 22nd. Mercury and Saturn reach conjunction on the Sun’s far side on the 10th and 13th respectively and remains hidden in the Sun’s glare.

Mars rises at about 05:15 throughout January and brightens a shade from magnitude 1.6 to 1.4 even though its location one hour before sunrise drops from 12° to 9° in the south-south-east. Tracking eastwards against the stars, it stands 6° below-left of the Moon and 7° north of Antares, the lead star in the aforementioned constellation of Scorpius, on the 20th. Another pulsating red supergiant, Antares has a name which derives from the Greek for “rival to Mars” because of its colour, though it is currently brighter than the Red Planet.

Diary for 2020 January

3rd 05h First quarter

4th 09h Peak of Quadrantids meteor shower

5th 08h Earth closest to Sun (147,091,144 km)

7th 22h Moon 3° N of Aldebaran

10th 15h Mercury in superior conjunction

10th 19h Full moon and penumbral lunar eclipse

12th 00h Moon 1.3° N of Praesepe

13th 12h Moon 4° N of Regulus

13th 15h Saturn in conjunction with Sun

17th 04h Mars 5° N of Antares

17th 13h Last quarter

20th 15h Moon 7° N of Antares

20th 19h Moon 2.3° N of Mars

23rd 03h Moon 0.4° S of Jupiter

24th 22h New moon

27th 19h Venus 0.1° S of Neptune

28th 07h Moon 4° S of Venus

This is an extended version, with added diary, of Alan’s article published in The Scotsman on December 31st 2019, with thanks to the newspaper for permission to republish here.