The sky: Last chance to spot Pot before winter

By IAN GRIFFIN*

This is the month of "the Pot" in the evening sky, and it will be our last chance to see it for a while.

The Pot is a peculiarly New Zealand name describing the central part of a region astronomers elsewhere call Orion. In summer it is high in the sky, but with the approach of winter each night brings it closer to the horizon as the sun goes down.

By month's end, the Pot will be lost in the glare of the sun's setting rays. So for a last glimpse of it, why not try spotting it and the region around it before then.

To find the Pot, face west after sunset. Its base is made of three bright stars forming a vertical line in the sky about a third of the way between the horizon and the overhead point.

From top to bottom, the stars are called Alnitak, Alnilam and Mintaka. They are noticeably blue in colour, and astronomers have calculated that each of them outshines our own star, the sun, many thousands of times.

They look like dim points of light only because they are incredibly far away - each is more than 1000 light years distant.

The pot's handle is made up of a curve of dimmer stars pointing south.

If you have a pair of binoculars, a peek at the handle of the Pot will reveal that one of the "stars" is actually a fuzzy patch of light.

Astronomers call this a nebula, and inside its glowing clouds of gas and dust new stars are forming.

To the left (or south) of the Pot is the brilliant blue-white star Rigel, while to the right (north) is a bright orange-coloured star called Betelgeuse.

Directly above the Pot is Sirius, the brightest star in the sky, which will probably be twinkling.

The line formed by Alnitak, Alnilam and Mintaka should be obvious once it gets dark. This Sunday, the crescent moon will be below and to the right of the Pot, while on Monday it will be level with and to the right of Betelgeuse.

The light hitting your eye as you gaze at this star began its journey more than six centuries ago, about the time Rangitoto last erupted.

Betelgeuse is an old star approaching the end of its life, and astronomers predict that its days will end in a massive explosion.

It is amazing to think that if this happened today, the star's tremendous distance means that we would not see the blast here until at least the year 2600.

* Ian Griffin is director of the Auckland Observatory and Stardome Planetarium.