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Playing hide and seek

ECLIPSE: The sun peeps out. Photo: AFP

ECLIPSE: The sun peeps out. Photo: AFP  

Would you like to witness the solar eclipse on October 3? Make your way to the planetarium.

The plane in which the earth moves around the sun is known as ecliptic plane. The moon moves in a smaller orbit around the earth. The plane of the moon's orbit is not aligned with the ecliptic, but it is inclined to the ecliptic plane by about five degrees. Because of this, only very rarely, the moon crosses the imaginary line connecting the sun and the earth. Whenever this happens, an eclipse of the sun takes place. Had this plane of the moon aligned with the ecliptic plane, every new moon day an eclipse of the sun would have occurred and every full moon day an eclipse of the moon would have occurred.

By an extraordinary coincidence, the moon appears as big as the sun in the sky. This is why during a total eclipse of the sun, the moon completely blocks the sun. This is due to the fact that, though the moon is smaller than the sun, it is nearer to us. That is the sun is 400 times bigger than the moon at the same time it is 400 times farther than the moon.

The moon moves in an elliptical orbit around the earth. Due to this, the moon sometimes comes closer to the earth and some times goes farther to the earth. Its distance from the Sun varies from 3,57,200 km to nearly 4,07,100 km. When it is farther away, its apparent size as seen from the earth slightly diminishes. During this time if an eclipse of the sun takes place, the moon will not be able to completely block the entire sun. An annulus of the outer regions of the sun will still be visible during the maximum eclipse. So this kind of eclipse is known as annular eclipse.

One such annular eclipse of the sun will take place on October 3. The annular phase of the eclipse will be visible in parts of Europe, North African countries and in Indian Ocean. The eclipse begins at 13:05 hours (IST) and ends at 18:59 hours (IST)

India, Western Asia, Europe and most of the Africa will witness partial phase that is only a fraction of the sun will be covered by the moon. In Chennai 38.5 per cent of the diameter of the sun will be covered. In Chennai, the eclipse begins at 16:25 hours (IST) and ends after the sunset.

It is unsafe to look at the sun directly. Even during partial or annular eclipse one should not attempt to view the sun without any eye protection. Permanent eye injury or loss of eyesight will result.

At B. M. Birla Planetarium, Periyar Science and Technology Centre, Gandhi-mandapam Road, Chennai-25, elaborate arrangements will be made for the public to witness the eclipse safely from 16:25 hours on October 3.

Courtesy: B.M. Birla Planetarium

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