The Hindu : New Delhi News : A celestial spectacle for night sky watchers

Online edition of India's National Newspaper
Saturday, Mar 04, 2006

New Delhi

New Delhi

A celestial spectacle for night sky watchers

Gaurav Vivek Bhatnagar

NEW DELHI: Delhiites will be able to witness a celestial spectacle this coming Sunday night as a beautiful configuration of jewel-like stars would be seen around the moon with the stars of Pleiades first shining around it and then moving behind the Earth's satellite one by one.

According to Nehru Planetarium Director N. Rathnasree, such an occultation of Pleiades can be viewed in North India from around 7-30 on Sunday evening. To get a clear picture, night sky watchers will have to keep the moon in sight through their binoculars or telescopes. And then they will be surprised to see bright activity all around it. The stars will first surround the half-lit moon and then move behind it.

Around 8-56 p.m., the first of these stars will then reappear behind the bright limb of the moon, adding slowly to the ring of jewels than can be seen under the bright limb of the moon.

Dr. Rathnasree said it would be easier to see these stars before the occultation begins as they are close to the dark limb of the moon. Close to the bright limb, when they reappear, they could easily be hidden in the glare from the bright portions of the moon.

Lunar occultation

She said a lunar occultation happens when a celestial body appears to have moved behind the moon. Such events happen very frequently, but in most cases the star being occulted may be very faint. However, when bright stars or planets such as Venus are occulted by the moon, it can be even seen with the naked eyes.

This time, Dr. Rathnasree said, binoculars or telescopes would be needed to view the spectacle. "The moon occupies about half a degree of the sky -- that is, its angular diameter is about half a degree. If one sees a bright star moving close to the moon, it is unlikely that one would see any other bright star within the same field of view. In general, one does not see reasonably bright stars very close to each other in the sky."

But, she said, there are a few exceptions to this. "In the winter evening skies, we see a cluster of stars in the sky which was described by Tennyson as `glittering like a swarm of fireflies tangled in a silver braid'. This cluster of stars is knows as the Pleiades or the Krittikas. When the moon moves in front of one of the starts in this cluster, it is likely that many of the other stars in this ground can be seen cluttered around the moon, giving a beautiful view through a good pair of binoculars."

And that is exactly what is on the cards this weekend.

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