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.
Jupiter and Orion rule our New Year nights
The annual Quadrantids meteor shower hits its intense peak even before Jupiter comes to opposition on the 5th. The giant planet shines brightly throughout our January nights and Orion, too, is ideally placed in a sky awash with bright stars.
What is missing, though, is any sign of Comet ISON. Any hopes that the comet might blossom into a spectacular sight during December were shattered when its icy nucleus failed to survive its brush with the Sun on 28 November. A so-called ghost of ISON did emerge from its perihelion, but this must have been a dispersing cloud of dust which soon disappeared. Searches since then, including by Hubble, have failed to spot anything at all. So much for the Comet Of The Century.
Our charts show the Pleiades in Taurus glimmering high in the south at our map times as Orion strides towards the meridian. Trailing Orion are his two dogs, Canis Major and Canis Minor, with their bright stars Sirius and Procyon. Together with Betelgeuse at Orion’s shoulder, these form the Winter Triangle. Orion’s immediate foe, of course, is Taurus the Bull whose main star Aldebaran lies against a more remote V-shaped star cluster, the Hyades. The tips of the bull’s long jutting horns are marked by the stars Elnath and Zeta Tauri and it is just 1.1° north-west of Zeta that we find the famous Crab Nebula. The debris from a supernova explosion recorded by Chinese astronomers in 1054, it lies about 6,500 light years away and appears as an oval eighth magnitude smudge through a telescope.
January sees the Sun climb 6° northwards as 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 new on the 1st, at first quarter on the 8th, full on the 16th, at last quarter on the 24th and new again on the 30th.
With no moonlight, and if the weather permits, this could be good year for Quadrantid meteors. The shower lasts from the 1st to the 6th but has an unusually brief peak when the meteor rate could reach 80 or so per hour for an observer under ideal conditions. That peak is expected at about 19:00 GMT on the 3rd when the radiant, the point in the sky from which the meteors diverge, lies rather low in the north so that only a fraction of the ideal number of meteors may be seen. Even so, I’d expect to see several long-trailed meteors speeding overhead from north to south. Later in the night, the radiant follows the Plough as it climbs through the eastern sky.
The brightest object on our charts, Jupiter, shines at magnitude -2.7, three times brighter than Sirius, when it stands opposite the Sun on the 5th. It then rises in the north-east at sunset, crosses our high meridian at midnight and sinks to set in the north-west at dawn. The arrow on our chart shows it tracking westwards against the stars of central Gemini, some 10° below and right of Castor and Pollux. As such, it is unmistakable above and to the left of Orion later in the night. Look for it to the left of the almost-full Moon on the evening of the 14th. Jupiter is 630 million km distant at opposition, its slightly rotation-flattened disk measuring 47 arcseconds in diameter.
Appearing even larger than Jupiter is the dazzling magnitude -4.3 evening star Venus which sinks from 10° above Edinburgh’s south-western horizon at sunset on the 1st to set itself 100 minutes later. A full arcminute in diameter but only 4% illuminated, its slender crescent is obvious through binoculars. Weather and horizon permitting, the view may be more stunning on the 2nd when Venus lies 2.7° below-right of the narrow arc of the 2% illuminated Moon.
Venus soon disappears from our evening sky as it sweeps through inferior conjunction on the Sun’s near side on the 11th. Within another four or five days, though, Venus reappears as a morning star in the south-east and by the 31st it rises two hours before the Sun, shines at magnitude -4.6 and is a 12% sunlit crescent 52 arcseconds across.
Mercury emerges as an evening star later in the month as it moves to lie 18° east of the Sun on the 31st. Between the 19th and 31st, its altitude in the south-west forty minutes after sunset doubles from 4° to 8° as it dims only slightly from magnitude -0.9 to -0.5. Use binoculars to spy it in the twilight if you have a favourable horizon.
Mars rises in the east in the middle of the night and is tracking eastwards against the stars of Virgo to pass 5° north of Spica on the 28th. Its pink-red glow brightens from magnitude 0.8 to 0.3 and its disk swells to 9 arcseconds by the month’s end, large enough for some surface detail to be visible telescopically. It is best to observe it when it is highest as it crosses the meridian at an latitude of almost 30° shortly before dawn. The Moon lies alongside Spica and below Mars on the 23rd.
Saturn, another morning object, is creeping eastwards in Libra, about 6° to the east (left) of the wide double star Zubenelgenubi. It rises in the east-south-east at about 04:20 on the 1st, two hours earlier by the 31st, and at mag 0.6 to 0.5 is the brightest object low down in the south before dawn. When it lies alongside the Moon on the 25th, its disk appears 16 arcseconds wide while its glorious rings are 37 arcseconds across and have their north face tipped 22° towards us.