Going to be once in a "blue" moon

Sky gazers await once in a blue moon phenomenon on New Year's eve. Announcing this to reporters in Chennai today, Director of Birla Planetarium P Iyamperumal said the lunar eclipse on 31 December can be viewed in Chennai and the annual solar eclipse on 15 January, a rare happening after 108 years, can be viewed from Kanyakumari.

'The lunar eclipse will take place from 12.21 pm to 1.24 am. About 80 per cent of the eclipse can be viewed from Chennai. It can be watched with the naked eye,' he said.

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Stating that special arrangements had been made at the planetarium to watch the eclipse, he said an exclusive goggle is needed for the purpose.

Meanwhile, an agency report from New Delhi said when a second full moon in a calendar month appears in the night sky, the occurrence is known as a blue moon.

There are 12 full moons most years but every two or three years there is an extra full moon which is called a blue moon.

'We've already had a full moon on 2 December and the next one is on New Year’s Eve that is on 31 December,' Science Popularisation Association of Communicators and Educators (SPACE) president C B Devgun said.

On rare occasions the moon actually had a blue appearance - often caused by smoke from large-scale fires or excessive dust particles in the atmosphere.

Explaining the phenomena of bue moons, Devgun said the moon cycle takes about 29.53 days to complete that is almost a month. That is why there's one full moon once a month, at least on most years.

'Because the lunar cycle does not reach a full 30 days, the full moon happens about a half-a-day earlier each month. So over time, this small difference eventually pushes the date of the full moon until there can be two full moons in one month. When this happens, the second full moon in that month is called the blue moon,' Devgun said.

This comes about quite rarely, only about seven times in 19 years, which is equal to one blue moon every 2.7 years more or less.

The next blue moon will occur on 21 November, 2010. After that, planet watchers will have to wait until 21 August, 2013, to see another blue moon.