24-02-2007 March night sky (Article 74)

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Simon Kenny
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Location: Shannon, Co. Clare, Ireland

24-02-2007 March night sky (Article 74)

Post by Simon Kenny » Wed Feb 04, 2009 10:43 am

March night sky (Article 74)

This month the part time gardener in us wakes from winter hibernation and digs the lawn mower from the shed.

This is a consequence of Earth’s 5 billion year relentless orbiting of a star we call the Sun. If Earth’s axis was not tilted 23 ½º from its plane with the Sun we would have no seasons. Orbiting the Sun allows us to see the different star groupings, called constellations, in the surrounding neighbourhood of our solar system. It takes 12 months of solar orbiting to see all our stellar neighbours before the cycle starts again. This is why all the major winter constellations have nearly set in the west when the sky darkens, only to be replaced by the Spring constellations like Leo and Virgo creeping further over the eastern horizon each evening.

Virgo is a large constellation with only one really bright white star called Spica above the SE horizon from about mid March. When looking at Virgo we are actually looking out and away from our home galaxy, the Milky Way. What makes Virgo very interesting is the cluster of thousands of galaxies that lie in this direction. A typical galaxy contains billions of stars and some of these galaxies are as big and even bigger than our home galaxy. They lie mind blowing distances from Earth and even with a large amateur telescope they visually appear as just smudges of light.

Mercury has now moved around the Sun and is a morning object rising at 05:47 on 2 March, and skirting the E/SE horizon through March. (Warning: do not use a telescope or binoculars with the Sun above the horizon — instant blindness will occur). On 1 March the waxing gibbous Moon will be 12.8 days old and 96% of its disc will be illuminated by the Sun.

On 1 March from about 18:00 Saturn will be well above the SE of E to horizon and will lie just below the Moon (7oclock position) and will climb higher in the sky to lie S of SE on 31 March, when it will not be dark enough until after 19:00. All through March Venus will shine brightly by reflected sunlight from its cloud tops. On 1 March it will lie unmistakably about 17º above the horizon in a SW to W direction with 87% of its disc illuminated by the Sun. By 31 March it will be 31º above a SW of W horizon with only 79% of its disc illuminated but it will have become a little brighter. The reason is because the orbit of Venus lies between Earth and the Sun, and on the 1 March it is 127.1 million miles from Earth while on 31 March it is nearer at 114.5 million miles. Despite it’s reduced reflected sunlight being nearer to us means it will be larger and thus brighter.

Jupiter rises at 02:19 on 1 March but only gets to 14º above the horizon through March in a dawn bright sky. Mars rises at 05:19 on 1 March but in an even brighter dawn sky. Clear skies!

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