The Night Sky This Week

by Mark Armstrong

16 - 31 March

What's up this week? Our weekly guide to the night sky will point you to all the planetary goings on, as well as pick out some deep sky objects for your viewing pleasure. Let's get started with a round-up of the Solar System, or follow the links above to jump to your favourite section.

Solar System Round-Up

Let's hope for clear skies for the last two weeks of March, as there is so much Solar System action with Saturn's opposition taking centre stage and Mars still in the frame for visual and digital observers alike. Don't forget that British Summer Time (BST) starts at 1am local time on 28 March, with the clocks advancing by one hour to 2am BST.

Saturn
Saturn comes to opposition on 22 March and shines moderately brightly at magnitude +0.5 with a distinctly creamy hue. It nestles in the 'bowl of Virgo', just below the main concentration of galaxies on the Virgo/Coma border. By the time the sky is dark at around 7.30pm the ringed planet is about 15 degrees up, still climbing away from the house and treetops and all the murk hugging the eastern horizon. By 9pm most observers, including city-dwellers, should be able to get a 'scope on it and it culminates just after midnight in the south at a respectable 40 degrees altitude. Saturn is a splendid sight even through a small telescope; don't let the narrow angle of the rings put you off observing it. The rings have been steadily 'closing up' from our perspective in 2010 and at opposition they are tilted by just over three degrees. This process continues until May but then the rings open out again to a full ten degrees by the end of the year. Titan is Saturn's largest moon and can be seen in 10x50 binoculars but easier in a small 'scope. In the last fortnight of March it reaches greatest western elongation on 18 March can be seen mere arcseconds north of its parent on opposition night.

At dusk on 31 March, with the Sun six degrees below the horizon, Venus and Mercury make a splendid early-evening pairing. AN graphic by Greg Smye-Rumsby.

Mercury and Venus
Mercury rapidly reappears in the evening sky following superior conjunction on 14 March. In fact this is the best evening apparition of the year for the UK, with the elusive innermost planet reaching greatest elongation east (19.2 degrees) early next month. Mercury is brighter before greatest elongation and by 31 March at around 30 minutes after sunset it will be eight degrees above the western horizon shining at mag. -0.9 and telescopically sports a gibbous phase of 71 percent. This apparition has a real bonus as Venus joins in the fun, passing just over three degrees east of Mercury as it makes its serene progress away from the western horizon. Venus' presence really will help track down Mercury and given clear skies, it is worth making a special effort to secure a flat horizon, especially if you have never seen the planet. Furthermore, this conjunction should make for a really nice photo opportunity!

Mars
Once the inferior planets have been observed, swing your 'scope eastwards to Mars. Although well past opposition, the red planet still has much to offer and besides, March is probably the last good month to observe it. On 16 March as darkness falls around 7.30pm Mars is about an hour from culmination and is 60 degrees up in western Cancer. It is still a great sight, outshining everything bar Sirius and Venus at mag.-0.2. Through a telescope it is still above 10 arcseconds apparent diameter and given good seeing the dusky V-shaped wedge of the Syrtis Major, slap bang on the Martian central meridian, should be well seen. The red planet finally shrinks to under ten arcseconds on 23 March and by then you will need to stay up to 11.30pm to see the Syrtis Major at its best, with Mare Cimmerium in Mars' southern hemisphere favoured early evening. By the month's end Mars will have faded to mag. +0.16 and the great volcano Olympus Mons lies close to the central meridian.

The lunar graze of the star HIP 31696 (top) and the profile of the lunar limb that will be grazed on 23 March. AN graphics by Greg Smye-Rumsby.

Lunar occultation
There is a good lunar occultation on the early morning of 27 March. The wide double star omicron Leonis with components of mag. +3.5 and +9.5 separated by 85 arcseconds, will disappear at the dark limb of a waxing gibbous moon at 1.51am for observers in Edinburgh and at 1.59am for those in London. There is a grazing lunar occultation too on the evening of 23 March, which is well worth checking out if you are lucky enough to be able to live on or travel to the narrow track. HIP 31696 (ZC 1017, mag. +6.8) appears to scrape along the dark edge of the gibbous moon with the graze track running across south-west Ireland from Clifden in County Galway to Waterford, crosses St George's channel and heads across south-west England from Bude in Cornwall (10.15pm) to Slapton on the coast of Devon (10.17pm).

Dwarf planet Makemake
Heading into the frozen depths of the deepest Solar System, dwarf planet Makemake reaches opposition on 16 March, shining at a photon-challenged mag. +16.9. CCD observers using even small telescopes can image Makemake and its slow crawl eastwards against the backdrop of the stars of Coma Berenices will be detectable in a series of images taken a few nights apart. Centre your 'scope at R.A. 12h 35.29m and Decl. +28° 27.7' on opposition night. Moving back in towards the Sun, comet 81P/Wild is at it?s brightest at around mag. +9; it's best to chose the moonless third week of the month to attempt to track it down as it tracks through eastern Virgo, passing a couple of degrees south of iota Virginis.

Details of Comet 81P/Wild 2's path over the coming month.

Comets
Comet 81P/Wild is at its brightest this month at mag. +9 and is well worth tracking down as tracks through Virgo in the early morning skies. It should be picked up in 10x50 binoculars and an ideal time to try for it is mid-month when the Moon is at or close to new and the comet is around two degrees south of iota Virginis.

Happenings down under

It's up to Mars and Saturn to hold the fort on the planetary scene in the first half of March but the Moon steps in with some interesting occultations. There are also a number of comets well worth tracking down but alas nothing in the Hale-Bopp class.

Saturn
Saturn takes centre stage in March, reaching opposition in the second half of the month in Virgo. By 9pm local Sydney daylight savings time (EDT) the sky is truly dark and those with a clear eastern horizon should notice the creamy hue of the ringed planet about 10 degrees (about a fist's width held at arms length) up. By 11pm Saturn is well clear of all the muck and rubbish close to the horizon and the view through even a small 'scope will be pretty amazing. To the naked eye Saturn is not especially bright at this time at only mag. +0.6 and some observers may confuse it with Spica, only some 20 degrees south east of the ringed planet (about an outstretched hand). Saturn doesn't twinkle whereas Spica invariably will and this, together with the planet's distinct colouring, should be sufficient to avoid confusion. Some of Saturn's telescopic glory has been diminished by the shallow angle of the rings at present and this accounts for its relative dimness.

Saturn is over 30 degrees up in the east-north-east by 11pm local Sydney time. Graphic made using the Sky version 5 software http://www.bisque.com/sc/pages/thesky6family.aspx

Mars
Mars culminates around 10pm Sydney time at the end of the first week of Mars. It is still a glowing ember at mag. -0.44 and spans a respectable 11.5 arcseconds through the eyepiece; make the most of this months observing time as Mars fades rapidly. So what surface features can be seen or imaged if you have access to a moderate aperture, say a 150-mm? Luckily Mars' most prominent dark feature, the wedge-shaped Syrtis Major will be slap-bang on the central meridian around midnight in the first half of March. The use of colour filters will enhance Martian surface features with a red (Wratten 25), orange (Wratten 21) or yellow (Wratten 15) doing the job on dusky dark markings. By the end of the second week the Tharsis region will be on show early evening; there have been many high altitude orographic white clouds seen and imaged over Tharsis already, so look out for these; a blue filter (Wratten 44A, 80A), green (Wratten 58) or blue-violet (Wratten 47) will help.

The Moon
The Moon is very busy in the first week of March with the following occultations:

4/5th; HIP 69658 (mag. +5.5) is occulted by the Moon with the reappearance at the dark lunar limb (RD). Local times including any adjustments for daylight saving; Perth 11.06pm; Darwin 12.14am; Brisbane 1.33am; Adelaide 2.04am; Melbourne and Sydney 2.47am; Auckland 5.22am; Wellington 5.35am; Christchurch and Dunedin 5.36am.

Sixth magnitude HIP 69658 reappears from occultation on 4/5 March across Australia and New Zealand. This is how Perth observers will see it. Graphic made using Guide 8 software.

4/5th; HIP 69929 (CS Virginis, mag. +5.9) is occulted by the Moon (RD); Perth 12.43am; Darwin 2.24am; Brisbane 4.07am; Adelaide 4.15am; Melbourne 5am; Sydney 5.12am.

5/6th; HIP 74732 (mag. +5.5) is occulted by the Moon (RD). Perth 1.49am; Darwin 3.21am; Brisbane 5.13am; Adelaide 5.16am; Melbourne 6.01am; Sydney 6.15am.

Observers can enjoy a double lunar occultation reappearance on the morning of 8 March. This is the view from Wellington, New Zealand. Graphic made using Guide 8 software www.projectpluto.com

7/8th; Two sixth mag. stars occulted by the Moon (RD) within minutes of each other for observers in New Zealand. HIP 83176 (mag. +5.9) North Island (Wellington) 3.22am; South Island (Dunedin 3.23am. Then 26 Ophiuchi (HIP 83196, mag. +5.8) North 3.24am; South 3.30am.

Asteroids & comets
Also asteroid (249) Ilse occults delta Capricorni in daylight for narrow track across S.E. Australia. Times; Brisbane 1.14pm EST and Adelaide 1.44pm CDT. For more information visit: http://asteroidoccultation.com/2010_03/0308_203_23018.htm

Comet 29P/Schwassmann-Wachmann is an evening object in Leo close to the border with Cancer. This comet is prone to outbursts and it is currently undergoing one, with latest estimates having it hovering around mag. 10-11. 81P/Wild is in the eastern midnight sky among the stars of Virgo and appears to be holding steady at 9th magnitude and should be bright enough to be picked up in 10x50 binoculars; it is three degrees south of iota Virginis on 6/7 March. Comet C/2009 K5 (McNaught) is brighter than expected at mag. +10 but observers will need to be a night owl to track at down as it lives in Aquila at present and won't be at a decent altitude until close to dawn.

Deep Sky