Solstice approaches

It's nearly the summer solstice and there's a plethora of exciting events going on in the sky, writes Ian Griffin.

At 11.22am on December 22, the sun reaches the southernmost point in its annual journey around the sky. This is the exact moment of the summer solstice, which means that December 22 is the longest day of the year.

Here in Dunedin, with sunrise at 5.44am and sunset at 9.28pm, the sun will be above the horizon for 15 hours and 44 minutes.

While hours of darkness are at a premium, there is still a plethora of exciting events going on in the sky. In particular, over the weekend, early-rising stargazers across Otago get to enjoy a very close approach between the planets Mercury and Jupiter.

To see the close approach (which astronomers call a conjunction) you need to get up early, and find yourself a spot with an entirely unobstructed view towards the southeast.

In practice, it's probably best to find somewhere with a view of the ocean, since any obstructions will hide the planets from view, and the best chance of viewing the planets against a dark sky is when they are still relatively low.

The conjunction should be visible with the unaided eye, but as usual for events like this, I suggest you bring along a pair of binoculars to aid you in your conjunction hunt.

This week's chart is drawn for 4.45am on Sunday. Venus will be an unmistakable object, blazing low in the eastern sky. Once you find Venus, turn your eyes to the right, and scan the sky just above the horizon.

If you are lucky, and the sky is very clear, you should be able to spot Jupiter as a bright yellow-white star just clearing the horizon. Once you find Jupiter, you should be able to spot another slightly dimmer yellowish "star'' less than one degree away (that's about the distance subtended by your little finger at arm's length).

Both planets will be rising as darkness fades, and by about 5.15am the sky will be too bright for you to spot them, so there really is a narrow window of time in which to observe this planetary close approach.

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