THE SOUTHERN CROSS

If you have a clear sky to the south early after dark, you will see the Southern Cross, or Crux, high in the sky, with the two bright pointer stars to its left.

The Southern Cross is a bit like the hands of a clock for us here in the south, as it moves continuously around the point in the sky that is due south.

It is actually Earth, rotating on its axis, that causes this apparent motion by the stars.

The Cross, however, doesn't keep perfect time as a clock, since it makes one full circle plus four extra minutes every 24 hours.

So depending on what time of year and time of night you are looking, it will be in different positions all around the circle, always followed by the two pointers to help you find it.

The pointers are called Alpha and Beta Centauri, the brighter of the two being the "alpha" star in the group.

Alpha Centauri is the closest visible star to the Sun, and is not a single star at all, despite how it looks to our eyes.

It is a star system consisting of two sun-like stars that orbit each other very closely, plus a third very dim star that we can't see without a strong telescope.

The third one, called Proxima Centauri, comes closer to us than the other two.

In addition to being the closest star, Alpha Cen is also the third brightest star in the sky, from anywhere on Earth, and it takes almost four years for its light to arrive here on Earth.

Our photographer, Fraser Gunn, is part of a research project at Mt. John Observatory looking for planets in the Alpha Centauri system.

THE PLANETS

Mercury appears as a much dimmer version of Venus, the usual "evening Star" in the west.

Look for it around 45 minutes after the Sun goes down.

The moon is growing toward its fullest point which will be during the wee hours of Wednesday morning.

Already at the beginning of the week its brightness is obscuring all but the brightest objects.

Looking north, the brightest things you will see (besides the moon of course) will be Mars on the left, then higher and to the right Saturn with the star Spica above it, and farther right and lower than the others is the star Arcturus.

If you can manage to be awake a couple of hours before the Sun, 6am or 6.30am should be good for most of the country (depends on your location and whether you are surrounded by mountains), you will see a special sight: the breathtakingly brilliant morning "star" Venus accompanied by dimmer, but still quite bright, Jupiter to its left.

If they aren't up yet when you go out to look, wait for it, as they are a very beautiful pair shining out of that predawn deep blue sky above the eastern horizon.

- © Fairfax NZ News

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