A Close Encounter between 2 Planets & a Swarm of Stars - 15 to 17 June 2006

A close encounter between the red planet Mars and the ringed planet Saturn was promised in mid June, and Mars was to pass right through the Beehive star cluster in Cancer. Unfortunately, the planets were near the end of their 2005/2006 encounters with the Earth (that is, well past Opposition), so from the latitude of the UK were low in the west after sunset so would not be seen in truly a dark sky.

This was definitely a binocular / telescope event because Mars, the fainter of the two planets at magnitude +1.5, was hard to see so low down in the not quite dark sky, and the Beehive stars were individually much fainter than that, although there are dozens of them.

This map shows the positions of Mars and Saturn within the constellation of Cancer on 16th June, with Mars slap bang in the Beehive. Each vertical line represents 10 minutes or 2.5 degrees of Right Ascension (longitude), so Mars and Saturn are currently about 1.5 degrees (or 3 Moon diameters) apart.

The Encounter

Although the UK was having a spell of warm sunny weather around the critical dates, the sky was frequently veiled with a thin layer of cirrus clouds. The obscuring effect was especially noticeable nearer the horizon, so the view was nowhere near as clear as it should have been. A couple of weeks earlier the Beehive, with Saturn nearby, was a fine sight in binoculars when still further from the Sun (i.e. a little higher in a darker sky), but by now there was just too much cloud and light in the sky to see it.

I managed binocular views on all three days, and brought my Helios 80mm refractor to bear on the 16th, with Mars in the Beehive, but this was the worst day for cloud so none of the stars were seen and no decent photos were obtained. Here is a photo from the 15th, which shows Saturn, clearly the brighter of the two planets, just above the star Delta (47) Canceri. This star, considerably fainter than either planet, lies just below an aircraft trail in this 4 second exposure, but nothing of the Beehive, which lies to the left of Mars, is visible.

Saturn and Mars on 15 Jun 2006

Saturn and Mars at 2142UT (2242BST) on 15 Jun 2006.

Minolta Dimage 7, 37mm plus 1.5x teleconverter; 4s @ f/3.4, ISO400

By switching between photos from the 15th and 17th the movement of Mars compared to the much more slow moving Saturn is plain to see. The following pictures are aligned on Saturn so roll the mouse over to see Mars move.

Saturn and Mars on 15 (2142UT) and 17 (2131UT) Jun 2006.

Minolta Dimage 7, 37mm plus 1.5x teleconverter; 15th = 4s @ f/3.4, 17th = 1.4s @ f/3.4, ISO400

To put the small distance between the planets into perspective, this photo puts them in the context of their surroundings - shrinking the picture for the internet renders them practically invisible, so the inset shows them as they are on the original photo.

Wide view of Mars & Saturn, 17 Jun 2006

Compare the picture above with the one below taken on 21 May 2004, from almost the same place - the street lamp to the left is the same one in both instances. Mars and Saturn were beside each other again, but in the intervening 2 years 1 month Saturn has moved on by 25 degrees (it takes 30 years to orbit the Sun), Mars has completed one circuit of the Sun, plus 25 degrees, and the Earth of course has completed a little more than 2 circuits of the Sun.

Saturn, Mars, Moon and Venus; 21 May 2004


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