Inconstant stars in stunning New Year sky
Our evening sky is bursting with stellar interest but devoid of bright planets. Instead, Mars partners Jupiter in the predawn in the south-east to south while the impending spectacle of the annual Quadrantids meteor shower is rather blunted by bright moonlight.
The charts show Taurus high on the meridian, above and to the right of the unmistakable form of Orion whose brightest stars are the distinctly reddish supergiant Betelgeuse and the contrasting blue-white supergiant Rigel.
Between them lie the three stars of Orion’s Belt, while hanging below the middle of these is his fainter Sword with the Orion Nebula. The latter’s diffuse glow, visible to the unaided eye under decent conditions and obvious through binoculars, comes from a region where new stars and planets are forming. It lies some 1,350 light years away and is one of the most intensively studied objects in the entire sky.
Two iconic variable stars, Algol and Mira, are well placed in the evening. Algol in Perseus, the archetype of eclipsing variable stars, has two unequal stars that orbit around, and hide, each other every 2 days 20 hours and 49 minutes. Normally Algol shines at magnitude 2.1 and is almost identical in brightness to the star Almach in Andromeda, 12° to its west and labelled on the chart.
However, when Algol’s fainter star partially obscures its brighter companion, their combined light dips to magnitude 3.4, one third as bright, in an eclipse that lasts for about 10 hours and can be followed with nothing more than the naked eye. This month, Algol is at its mid-eclipse faintest at 02:45 on the 13th, 23:34 on the 15th and 20:23 on the 18th.
Mira, by contrast, is a single red giant star that pulsates in size and brightness every 332 days on average. It lies well to the west of Orion in Cetus, the sea monster of Greek mythology which was slain by Perseus when he rescued Andromeda.
During a typical pulsation, Mira varies between about magnitude 3.5, easy for the naked eye, and the ninth magnitude, probably needing a telescope. Unlike Algol, whose variability is like clockwork, Mira is less predictable and it has been known to touch the second magnitude, as it did in 2011. Now is the time to check, for it is close to its maximum as the year begins. Markedly orange in colour, it dims only half as quickly as it brightens so should remain as a naked-eye object throughout January.
Named for the extinct constellation of Quadrans Muralis, the Quadrantids meteors diverge from a radiant point in northern Bootes which lies low in the north at our map times and climbs to stand high in the east before dawn. Meteors are seen between the 1st and 6th but peak rates persist for only a few hours around the shower’s peak, due this time at about 21:00 on the 3rd when 80 or more meteors per hour might be counted by an observer with the radiant overhead in a clear moonless sky. However, with the radiant low in the north and moonlight flooding the sky at the time, expect to see only a fraction of these, perhaps trailing overhead from north to south.
Earlier on the 3rd, at 06:00, the Earth reaches perihelion, its closest point to the Sun in its annual orbit. Edinburgh’s sunrise/sunset times change from 08:44/15:49 on the 1st to 08:09/16:44 on the 31st. The Moon is full at 02:25 on the 2nd, only four hours after it reaches its closest point to the Earth for the entire year. There is a relatively modern obsession in dubbing such an event a supermoon, because the Moon appears 17% wider than it does when at its furthest. The difference between an average full moon and this one, though, is hardly “super” and far from obvious to the eye.
The Moon’s last quarter on the 8th is followed by new on the 17th, first quarter on the 24th and full again on the 31st when it passes through the southern half of the Earth’s shadow in a total lunar eclipse. Sadly, the event is over before sunset and moonrise for Britain.
Venus slips around the Sun’s far side to reach superior conjunction on the 9th and leave Jupiter as our brightest morning planet. Seen from Edinburgh, the latter rises in the east-south-east at 04:04 on the 1st and is climbing more than 15° high into the south before dawn. Conspicuous at magnitude -1.8 to -2.0, it creeps 4° eastwards to the east of the famous double star Zubenelgenubi in Libra and rises at 02:30 by the month’s end.
Mars, much fainter at magnitude 1.5, lies almost 3° above-right of Jupiter on the 1st and tracks more quickly eastwards to stand only 14 arcminutes (half a Moon’s breadth) below Jupiter before dawn on the 7th. The pair lie below the waning Moon in our predawn sky on the 11th when Jupiter’s cloud-banded disk 34 arcseconds wide and visible through any telescope, while Mars is still too small to appear interesting. Mars is brighter at magnitude 1.2 and stands 12° to the left of Jupiter by the 31st.
Mercury, bright at magnitude -0.3, may be glimpsed through binoculars as it hovers very low above our south-eastern horizon for more than 90 minutes before sunrise until the 8th. Given a clear horizon it may still be visible on the 15th when it stands 2.6° below-right of the vanishingly slender waning Moon. Saturn, half as bright at magnitude 0.5, lies 4° right of the Moon on that morning but is easier to spot by the month’s end when it rises almost two hours before the Sun.
This is a slightly revised version of Alan’s article published in The Scotsman on December 30th 2017, with thanks to the newspaper for permission to republish here.
Moon between Venus and Mars on the 2nd
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 1st to the 6th, the shower is due to reach its maximum at about 15:00 GMT on the 3rd. 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 3rd, 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 1st, 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 2nd 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 14th. 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 12th.
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 4th 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 1st to 08:09/16:44 on the 31st. The Moon is at first quarter on the 5th, full on the 12th, at last quarter on the 19th and new on the 28th.
The Moon lies below the Pleiades on the evening of the 8th 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 8th 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 1st and at 23:37 on the 31st. 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 19th 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 6th onwards to glimpse Mercury. This reaches 24° west of the Sun on the 19th and brightens from magnitude 0.9 on the 6th to -0.2 on the 24th when the waning earthlit Moon stands 3° above Saturn.
This is a slightly-revised version of Alan’s article published in The Scotsman on December 31st 2016, with thanks to the newspaper for permission to republish here.
Quadrantids bring New Year fireworks on the 4th
If one of our resolutions for the New Year is to get to grips with the sky at night, then we could hardly do better than start with our January evenings. The unmistakable constellation of Orion the Hunter rises in the east at nightfall and is the centrepiece of a star-strewn region in the south-south-east by our star map times. On the other hand, most of the brighter planets, and what may be our brightest comet of 2016, are best seen in the morning sky.
Just as last month brought the Geminids as the best meteor shower of 2015, so the imminent Quadrantids shower may provide our best display of 2016. Lasting from today until the 6th, but with most of its activity in the hours before dawn on the 4th, its medium speed meteors are seen in all parts of the sky but diverge from a radiant point below and left of the Plough’s handle. The Plough itself lies in the north at nightfall and climbs through the north-east and east to lie overhead before dawn.
Most of the constellation figures show little relation to the things, persons or animals they represent. Orion is a striking exception, for he has conspicuous stars at his shoulders and knees and an iconic line of three stars to define the belt around his waist. Admittedly, his head is marked only by a knot of fainter stars, although if we look carefully we can find an arc of other faint stars to represent the shield he holds in the face of the charging bull, Taurus. Another line hangs below his belt to form his sword.
Use binoculars or a telescope to inspect the sword and it is easy to spot the Orion Nebula, a cloud of gas and dust that lies some 1,350 light years away. This miasma of greens, reds and blues is a region where new stars are forming, together with their nascent planetary systems.
The line of Orion’s belt slants downwards to the brightest star Sirius in Canis Major, the larger of Orion’s two dogs. Extend the line the other way and we reach Taurus with its leading star Aldebaran in and the Pleiades star cluster. As Orion sinks towards our western horizon early on the morning of the 20th, Aldebaran is once again occulted by the Moon. As seen from Edinburgh, the star disappears behind the upper edge of the Moon just before 03:24.
It may be hard to believe, but the Earth is closest to the Sun for the year (147,100,176 km) when it reaches perihelion late tomorrow. Sunrise/sunset times for Edinburgh vary from 08:44/15:49 today to 08:10/16:42 on the 31st, while the Moon is at last quarter tomorrow, new on the 10th, at first quarter on the 16th and full on the 24th.
Jupiter rises at Edinburgh’s eastern horizon at 22:39 tonight and two hours earlier by the 31st. Now in south-eastern Leo and already twice as bright as Sirius, it brightens from magnitude -2.2 to -2.4 this month and reaches a so-called stationary point on the 8th when its easterly motion reverses to westerly. If you did get a telescope for Christmas, then enjoy the view of its fascinating cloud-banded disk which swells in diameter from 39 to 42 arcseconds. Jupiter stood near the Moon last night and the two are even closer on the 28th-29th.
Mars rises in the east-south-east by 02:15 and lies to the left of Spica in Virgo as they pass 25° high in the S before dawn tomorrow. The Moon is nearby on Sunday and even closer on 1 February, by which time Mars has travelled east-south-eastwards into Libra where it lies just above the double star Zubenelgenubi. Mars improves from magnitude 1.3 to 0.8 to overtake Spica in brightness, but is shows only a small 6 arcseconds disk through a telescope.
Venus continues as a brilliant morning star (magnitude -4.1 to -4.0) though its altitude in the south-east at sunrise sinks from 15° today to 8° by the 31st. It lies to the right of the waning Moon on the 7th when a telescope shows its disk to be 79% sunlit and 14 arcseconds wide. Venus is just 2° to the right of Saturn on that morning and within 7 arcminutes of Saturn on the 9th. At magnitude 0.5, Saturn is much the fainter of the two as it creeps eastwards in southern Ophiuchus.
Mercury has a few more days as a difficult evening star. It is bright at magnitude -0.2 tonight, but it hugs our south-western horizon at nightfall and sets less than 100 minutes after the Sun. As the month ends it is back in our morning twilight, a few degrees to the left of Venus.
Comet 2013 US10 Catalina has remained stubbornly below naked eye brightness in our morning sky, though photographs reveal a striking divergence between its tails of dust and ionized gas, the latter being torn and billowed by the solar wind.
Following perihelion 123 million km from the Sun in mid-November, the comet is closest to Earth (108 million km) on the 17th. Likely to appear as a small greenish fuzzy blob through binoculars, it moves from less than 0.5° west of the conspicuous star Arcturus in Bootes this morning to lie 1.2° east of Alkaid, the star at the end of the Plough’s handle, before dawn on the 15th. It is currently around the sixth magnitude but may be a magnitude dimmer by the month’s end as it sweeps within 9° of Polaris and recedes on a trajectory that will never bring it back towards the Sun.