02-08-2008 August Night Sky (Article 148)

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Simon Kenny
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Joined: Tue Feb 12, 2008 9:17 pm
Location: Shannon, Co. Clare, Ireland

02-08-2008 August Night Sky (Article 148)

Post by Simon Kenny » Tue Dec 30, 2008 9:30 pm

August Night Sky (Article 148)

The end of the summer is officially here. August, the first month of autumn usually proves to be a better month for astronomy when compared to July. The long stretch in the day that was there in mid summer is starting to dwindle and the nights are coming in a lot sooner.
For the first week or so of the month, with a good flat western horizon after sunset, you might be able to spy the planets Venus, Mercury, Mars and Saturn at approximately 09.45pm. If you wait until 10pm, Mars and Saturn are more easily seen but will be right on the horizon. You must wait until the sun is well below the horizon before searching for these, do not look at the sun with binoculars or a telescope as instant blindness will result.
By 10pm, you might notice a very bright looking star towards the south, this is the planet Jupiter in the constellation Sagittarius, it is unmistakable as it is easily the brightest star in that section of the sky, it will be visible all month long and almost any telescope will show it’s 4 star like moons, namely Io, Europa, Ganymede and Callisto. The disk of Jupiter will also be visible as a small disk and if you’re lucky you might be able to see it’s cloud bands stretching across it’s disk. If you wait until midnight when its dark enough, you might notice that Jupiter lies to the left of a rich part of the milky way, this glowing section of the sky stretches up and to the left and then to the north east, the milky way is infact our own galaxy.
The nights of the 10th, 11th and 12th of August is the peak time of the Perseid meteor shower, it usually gives the best meteor display of the year. Annually at this time, the Earth passes through a debris trail left over by comets, this debris hits the Earth’s atmosphere where it burns up, and we see it as meteors. At sunset, you are looking into space where the Earth has just been, after midnight the Earth has rotated on its axis enough so that you are looking into space where the Earth is moving into, for this reason you are more likely to see meteors after midnight. It’s akin to looking out the back window of a moving car between sunset and midnight and the front windscreen of a car between midnight and sunrise, you are not going to see many bugs hitting the back window of the car. The reason why this meteor shower is called the Perseids is that if you manage to draw all the meteors you see onto a star chart, nearly all of them will appear to be emanating from the constellation Persues, you get the same effect if standing on top of a bridge looking down on a motorway, from a distance the cars all appear to coming from a single point, they approach and finally wiz past you to your left and right.
Always remember never to look at the sun through binoculars or telescopes, as instant blindness will result.
The next club meeting is on Wednesday 6th August in room 207, Mary Immaculate College, Limerick.

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