Venus and Jupiter in conjunction

I hope many of you got to view the transit of Mercury across the sun, which took place last Tuesday morning.

I was lucky enough to witness the event from Cooks Beach Reserve near Whitianga in Mercury Bay, just a stone's throw away from the site where James Cook and Charles Green saw a similar transit almost precisely 250 years previously. Despite the low altitude, clear sky meant I got a superb view of Mercury's tiny silhouette crossing the sun.

After the excitement of a relatively rare transit, this week, I would like to draw your attention to another fascinating event called a planetary conjunction that is taking place in the western sky after sunset. A conjunction is the fancy name astronomers give to a close approach between planets.

This particular conjunction involves Venus and Jupiter, and it comes to a climax on Sunday night when the planets are separated by just under one and a-half degrees (or roughly three times the apparent diameter of the moon). The conjunction gives us a chance to compare the visual appearance of the two planets; Venus (which will be higher in the sky) will be the brighter of the two and will shine with a distinctly blue/white colour in contrast to Jupiter's predominantly yellow tone.

Of course, while the planets appear close together in the sky, this is just a line-of-sight effect. On Saturday, Venus is only 220 million kilometres from us, whereas Jupiter is more than 913 million kilometres away.

If you have binoculars or a small telescope, it should be possible to fit both planets into the same field of view. If you do this, you should easily be able to spot Jupiter's four major moons as bright points of light close to the planet. If you use a high-power eyepiece and zoom in, you should be able to see that Venus has a tiny disc, which this week is approximately 90% illuminated, and that Jupiter's disc appears three times bigger and is covered with distinctive cloud belts.

-By Ian Griffin

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