An exceptional celestial treat is in store for sky gazers as ‘supermoon’, the biggest and brightest full moon of the year which will be closest to Earth in 18 years, will be seen in the night sky on Saturday.

“The ‘supermoon’ will be closest to the Earth in 18 years tomorrow and will appear to be the biggest and brightest of 2011, Director of Science Popularisation Association of Communicators and Educators (SPACE) C.B. Devgun said on Friday.

Saturday’s full moon will be around 10 per cent bigger and 30 per cent brighter as compared to other full moons during the year, he said.

The term ‘Supermoon’ was first coined by Astrologer Richard Nolle in 1979. According to him, it is a situation when the moon is slightly closer to the Earth in its orbit than average, which is 90 per cent or more of its closest orbit, and the moon is a full or new moon.

On Saturday, the moon will be only 3,56,577 km away from the Earth, the closest while at the full moon phase in 18 years.

Earlier, there were supermoons in 1955, 1974, 1992 and 2005.

Regular situations of full moons coinciding with the moon’s closest point to Earth in fact happen after about every one year, one month and 18 days when it is about 3,63,104 km away from the Earth, Mr. Devgun said.

“This is because the moon’s orbit is an ellipse with one side 50,000 km closer to Earth than the other. In the language of astronomy, the two extremes are called ‘apogee’ (far away) and ‘perigee’ (nearby),” Mr. Devgun said.

At the closest, our natural satellite moon lies roughly 3,56,630 km from the Earth compared to its average distance of 3,84,800 km from the planet.

“The moon will not only shine brighter but will also appear bigger as compared to other full moons during the year,” he said.

The full moon will be at its best at around 3:30 a.m. R.C. Kapoor, a retired professor of Indian Institute of Astrophysics said.

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