Sky notes by Neil Bone 2008 December & 2009 January

ern limb, potentially a Sun, Moon and Earth spectacular sight with multiple disappearances The Sun reaches its most southerly position and reappearances behind on the celestial sphere at 12h 04m Universal lunar mountains. Scottish Time (UT; equivalent to GMT) on Decem- observers have grazes for ber 21, the time of the northern hemisphere mag +4.25 Merope winter solstice. For several days around this (along a line from NE to date, the Sun rises as far south of east, and SW Scotland), and mag sets as far south of west, as possible, mean- +5.18 Pleione (Black Isle ing that the hours of daylight are at a mini- to south of Skye). mum for the year. Also, the Sun cuts a low arc At New Moon on across the southern sky, making observations January 26, an annular more difficult for those attempting to follow solar eclipse occurs. The sunspot activity (the safe method of projec- track is mainly across the tion is best for most observers). Southern and Indian Sunspot activity has remained very low Oceans, and no part of throughout 2008, and the minimum between the event is visible from The waxing crescent Moon showing strong Earthshine on 2006 cycles 23 and 24 is the longest that most the British Isles. March 1. Neil Bone modern observers have experienced. The ex- pectation is that activity must surely pick up from view in the solar glare for the next few in 2009. It remains to be seen how the new months. Jupiter, too, is poorly placed, reach- cycle will turn out. Some have forecast a very ing solar conjunction on January 24. On De- rapid rise to a high spot-number maximum in The planets cember 31, the giant planet is a degree north 2010; other studies, however, suggest that of Mercury, and may prove a useful guide for long minima are usually followed by shallow, Mercury is visible in the evening sky from observers seeking out the more elusive inner- relatively low-activity maxima. We have much late December, reaching greatest elongation most world of our solar system. yet to learn about our local star! 19° east of the Sun on January 4. For about Saturn, in Leo just south of the Lion’s The Moon is New on December 27 and a week centred on this date, the planet sets ‘haunches’, is a good late evening object, ris- January 26, giving darkest evening skies in 90 minutes after the Sun, and an hour after ing around 22h UT in December. The ring the closing fortnight of either month – ideal, sunset stands about 5° above the southwest- system is now close to edge-on in its presen- in December, for giving new Christmas tel- ern horizon. Brighter than magnitude 0, tation towards us, and as a result, the planet escopes ‘first light’! Full Moon falls on De- Mercury should be reasonably easy to find appears fainter than in recent years, at mag cember 12 and January 11. December’s Full in the deepening twilight. The planet reaches +1.0. Not only do the rings reflect less light Moon in Gemini shines down from high alti- inferior conjunction between Sun and Earth towards us, they also show a narrow 0.5 tude in the midnight sky – not far from the on Jan 20. arcsecond diameter along their minor axis; position occupied by the Sun at noon in mid- Venus steals the show as a prominent small telescopes may not show them at all, summer – and its glare will swamp all but the ‘Evening Star’ throughout December and Janu- while in 150mm and larger instruments they brightest stars. ary, setting four hours after the Sun as the will appear as little more than linear exten- As it emerges into the evening sky after New Year begins. Greatest elongation 47° east sions to either side of the planet. New, the waxing crescent Moon is well pre- of the Sun is reached on January 14, and the While the rings’ narrow presentation robs sented at this time of year, thanks to the steep dazzling mag –4 planet is outshone in the Saturn of much of its grandeur – a pity for angle of the ecliptic to the western horizon. night sky only by the Moon itself: the 4-day 2009’s International Year of Astronomy; the By the time it is a 4-day crescent, the Moon waxing crescent will be 3° to Venus’ north on planet is usually a ‘wow’ object for the pub- in early January remains above the horizon the evening of Hogmanay, December 31. Tel- lic – there is at least a largely unobstructed for five hours after sunset. Earthshine on the escopically, Venus will show a diminishing view of the globe and its subtle cloud features non-sunlit part of the Moon may be promi- gibbous phase (similar to that of the Moon for observers using larger telescopes. nent at this time, the result of light reflected between first quarter and full) during Decem- The brightest and largest of Saturn’s satel- from Earth’s bright cloud-tops. ber. Dichotomy – half-phase – is usually lites, mag +8 Titan, can be found just over 3 A standout event in this interval is the reached a few days before greatest elongation arcminutes east of the planet on December 3 Moon’s passage through the Pleiades star clus- in evening apparitions (the so-called Schröter and 18, and January 4 and 20; it is due west ter early on the evening of Wednesday January Effect), and thereafter Venus exhibits a shrink- by the same angular distance eight days later. 7–8, during which multiple occultation events ing crescent phase, which is evident even in a will occur as stars disappear behind the dark, 60mm aperture instrument at a magnification leading (easterly) lunar limb. The Moon at this of ×30. As the phase decreases, Venus’ ap- time will be waxing gibbous, and quite glary – parent diameter grows, from 20 arcseconds a telescope will be needed to see these events in late December to nearly 30 arcseconds by Meteors to best advantage. For observers on a line from the end of January. This is a result of the southern East Anglia to the Isle of Wight, the planet coming closer towards the Earth. The glary, near-Full Moon wipes out any re- brightest of the Pleiades – magnitude +2.96 Mars reaches conjunction on the far side alistic prospect of observing the Geminids, Alcyone – will be grazed by the Moon’s south- of the Sun on December 5, and will be lost at maximum on December 13–14.

J. Br. Astron. Assoc. 118, 6, 2008 359 Sky notes

The Ursids, much less active and woefully range during December. A location chart with under-observed, are rather better placed in suitable comparison stars can be found on dark skies. Active from Dec 17–25, the shower p.104 of the 2008 BAA Handbook. Also in reaches maximum on December 22–23, usu- binocular range, fading from its early Novem- ally producing peak observed rates of per- ber peak brightness during December, is Chi haps 5–6 meteors/hr. Outbursts of higher ac- Cygni, now becoming a tricky object best seen tivity have been seen on occasion, and the in early evening or just before dawn. Ursids shower clearly merits greater atten- Each of these stars is best observed by tion than it normally receives. The radiant is making estimates at roughly weekly intervals circumpolar, close to the ‘bowl’ of Ursa Mi- to avoid bias. nor, and is high in the NNE sky late on a Eclipsing binary Algol (Beta Persei) has December evening. favourable minima for the British Isles on the The New Year opens with the short, sharp nights of December 4–5, 7, 24–25, 27–28 and maximum of the Quadrantids on Saturday Janu- 30, and January 16–17 and 19–20. During ary 3. Timing isn’t ideal for the British Isles, eclipses, Algol drops markedly in brightness with maximum expected around mid-day. How- from mag +2.1 to +3.4. ever, watches in the last couple of hours of the The well-known Hubble Space Telescope im- night of January 2–3 may catch the early part age of the ‘Spirograph’ nebula (IC418). of the rise towards maximum in dark skies, (NASA/STScI/AURA) with the radiant, in northern Boötes not far from Alkaid at the end of the Plough’s ‘han- Deep sky h3752, and from there it’s a half degree (a dle’, high in the eastern sky. Some activity Moon-width) hop ENE to the globular. 10×50 should still be evident in early evening on Janu- On midwinter nights, Orion dominates the binoculars show it quite well, and in a small ary 3–4, but at this time the radiant is low in southern midnight sky and, hardly surpris- telescope of 80mm aperture it is remarkably the northwest, and the first quarter Moon will ingly, is the focus for a lot of observers’ atten- prominent. At ×40 M79 shows as a circular make the sky unfavourably bright. Quadrantid tion. The splendid Orion Nebula M42 is al- haze about 6 arcminutes in diameter, with the meteors are quite slow, and in the hours imme- ways a favourite target, and the constellation core perhaps slightly offset to the west. diately after maximum can be bright, some- is home to a number of other attractions in- Lepus is also home to IC418, a planetary times showing strong blue or green colours. cluding the fainter nebula M78. nebula made famous by a Hubble image as Tucked below Orion’s ‘knees’ (Saiph and the ‘Spirograph’. This is one of many such mag 0 Rigel) is the quadrilateral of third-mag- objects which has a small angular diameter nitude stars marking the main part of Lepus, (10 arcseconds), appearing almost stellar in a sometimes rather overlooked constellation small telescopes. Use of an OIII filter, iso- Variable stars which contains a couple of deep sky objects lating the oxygen emission lines which are of note. The brighter is the globular cluster strong in such objects, makes IC418 stand The long-period variable Mira (Omicron Ceti) M79 (NGC 1904) one of very few such ob- out from the field stars and is a great aid to should be at maximum brightness at the end jects visible in winter skies. identification. At mag +9.2, of 2008, an easy naked eye target at perhaps At mag +7.8, and culminat- IC418 is relatively bright and is mag +3. Located just west of the triangle of ing less than 15° above the well within reach for an 80mm Alpha, Gamma and Delta Ceti (the Sea Mon- southern horizon from the aperture instrument. In my own ster’s head), Mira can have its brightness es- UK, M79 may seem a diffi- small telescope at ×40, IC418 timated using nearby constant-magnitude cult target, but it is surpris- appears almost stellar; at ×100, stars as comparisons. Mira will remain in ingly easy in small instru- it’s slightly diffuse with a strong naked eye range through January, and its slow ments. Location is straight- central condensation. The decline can be followed into early spring be- forward – a hop 4° south nebula is found just south of fore it becomes lost in the evening twilight. from Alpha and Beta Rigel, to the east of a parallelo- Another long period variable, U Orionis – Leporis (at the west of the Neil Bone’s drawing of IC418 gram of 7th-magnitude stars. near the upraised ‘club’ of Orion north of quadrilateral) takes the view with an 80mm refractor and Betelgeuse – should be coming into binocular to the 5th-magnitude star OIII filter. Neil Bone

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360 J. Br. Astron. Assoc. 118, 6, 2008