02-02-2008 February Night Sky (Article 123)

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

02-02-2008 February Night Sky (Article 123)

Post by Simon Kenny » Fri Jan 02, 2009 4:43 pm

February Night Sky (Article 123)

So far in 2008 there have not been too many opportunities to note the continuous position changes of the stars and their home constellations as they appear to drift across the sky from East to West. Even experienced observers can be surprised at just how much things change ‘up there’ when they have not seen the sky for a while. All of this change is of course caused by Earth’s relentless orbit around the Sun.

In the NW, the familiar W-shape of Cassiopeia and neighbouring Perseus are easy to find. The Plough hangs upside down in the northern sky and looks like a gigantic question mark. Due south lies the brightest star seen in our sky, Sirius, in the constellation Canis Major, and best seen this month.

Look SE at the constellation of Leo on 15th at 10pm, just below it you will find the planet Saturn. The rings of Saturn are now gradually closing, as observed from Earth. It will shine at magnitude 0.25 and will be about 40º above the horizon. It takes Saturn 29.4 earth years to make orbit the Sun and the tilt of its axis makes its rings appear to gradually open or close as it progresses through this orbit. The image below shows Saturn’s position relative to the constellation of Leo (the lion). The connecting lines help to show the impression of a crouching lion. Also marked in this image is the position of Saturn one year from now.

Just a few stats to take the breath away. The diameter of Saturn’s rings system is 171,000 miles compared to the minimum Moon to Earth distance of 227,000 miles! Saturn is now 773 million miles from Earth. The brightest star in the constellation of Leo is Regulus at 78 light years (LY) away, or 460,000,000,000,000 miles. Of the stars in the constellation of Leo, Regulus is the brightest and one of the nearest, with others at several hundreds of LY’s away and Eta Leonis at a staggering 2,174 LY’s.!

The stars that make up a constellation are only ‘a line of sight’ collection and as in Leo, the individual stars vary in size, brightness and distance from Earth.

The Moon rises at 04:48 on 2nd Feb. — much too late for most folks. However, at 6pm on 9th if you look to 15º above the West horizon you will see a 2.7 day old waxing crescent Moon with 8% of its disc illuminated. Watch it change over the coming evenings and on 15th at 19:00 it will be 9.2 days old waxing gibbous with 69% of its disc illuminated and about 64º above the horizon. Looking South it will be almost directly above the obvious 3 stars in the belt of Orion and just east of the Moon will be the distinctive orangey/red coloured planet Mars.

Mercury, Jupiter and Venus are not very favourable for observing during February.

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