Night Sky

Sky Notes for March 2012, with James Abbott

The long awaited conjunction between Jupiter and Venus takes place this month, with the two planets at their closest on the evenings of the 12th and 13th. Regular observers will have seen the gap between the two planets close over recent months and during the evenings around the conjunction Venus appears to move past Jupiter, a real time view of our dynamic Solar System.

With a closest separation of just 3 degrees, the two planets will be within the field of a pair of typical binoculars.

Venus-Jupiter conjunction (as shown in Stellarium)

The best time to look will be between 7pm and 9pm with the two planets setting at around 10pm in the West.

On the evenings of the 25th and 26th of March the young crescent Moon will pass by both planets, producing another close encounter. Spring is often a good time to see the “dark” portion of the young Moon lit up by Earthshine.

By mid-month, looking to the South East, Saturn is about 20 degrees up by 11pm. To the right of it and similar in brightness will be Spica, the brightest star in Virgo.

The Moon is Full on the night of the 7th/8th, passing about 10 degrees below Mars. The Red Planet reaches its closest point to the Earth on the 4th at a distance of about 63 million miles. This is much further than the closest approaches possible and so in a telescope the disc of the planet is modest at 14 arc seconds. Nevertheless, it will peak at mag -1.2 and at nearly 50 degrees in altitude when due South, Mars will be above the worst of the turbulence that causes bad seeing.

Daylight increases at its fastest for the whole year in March and with the clocks going forward to BST on Sunday 25th March, the change is dramatic. By the end of the month, Sunset is at 7.30pm and it is not fully dark until 9.30pm BST.

The stars appear to march in tune with the changing clocks. By late evening at the end of March, the familiar winter constellations are setting in the West, but in the North East the brilliant blue/white star Vega is already on show, a herald of the summer to come.

Also in the North East at the start of March is comet C/2009 P1 Garradd. The comet has been putting on a show for months and remains well placed in the late evening throughout March. Its starts the month at around mag 6.5 and from dark sites it is possible to make out parts of its extensive complex of tails even in binoculars and small telescopes.

Image of Comet 2009 P1(Garradd) by Rolando Ligustri

More information can be found on the BAA Comet Section website – http://www.ast.cam.ac.uk/~jds/

James Abbott is an astronomer, NEAS member and CfDS Regional Information Officer.

You can download a free map of the evening sky here:

The summer solstice takes place at about 12.30 BST on June 21st, just before local noon. The Sun will be nearly 62 degrees in altitude, the highest it can get from Essex. If the weather allows the Sun to shine, we can also see our shortest shadow of the year.

Venus, Mars and Saturn are now starting to line up nicely in the West after sunset and will be joined by the young Moon in mid-month. On the 15th, the crescent Moon will be near Venus, then on the 17th Mars and then on the 18th/19th Saturn. In each case the Moon will be to the left and slightly below the planet.

Summer twilight is at its maximum during late June so the sky is never fully dark from Essex, restricting the opportunity to see the stars. But it is often the best time to see Noctilucent clouds, in the north just above the twilight arch. To see these “night shining” clouds, find a fairly clear northern horizon and have a look from about 22.30 BST onwards.

Full Moon will be on the night of the 26th/27th when our partner in space appears to glide low, just over 14 degrees in altitude, over the Southern horizon at 1.30am BST. Co-incidently, Pluto, which is a similar physical size to our Moon, will be along the same line of sight although being about 40 billion times fainter than the Moon and lost in its glare will not be visible !

In the second half of July as twilight recedes and darker skies return, there will be a window of opportunity around midnight to see Pluto visually with telescopes of about 300mm aperture and upwards.

The NASA New Horizons mission to the Pluto-Charon system and the Kuiper belt has the potential to be as inspiring and surprising as the Voyager and Pioneer probes. As well as a fly-by of Pluto, New Horizons will spend 5 years exploring the Kuiper Belt and given the exotic discoveries of Voyager – such as nitrogen geysers on Triton, there are bound to be more surprises. Who would bet on how far out, and how cold, these icy bodies can still show activity !

New Horizons is now approaching the orbit of Uranus but still only just over half way to Pluto, where it will arrive in July 2015.

Just before launch, 2 new Moons in the Pluto system were discovered, Nix and Hydra, but there may be more. Like our Earth-Moon system, Pluto and Charon could be described as a double planet.

You can find a wealth of information including the current position of New Horizons at

http://pluto.jhuapl.edu/index.php