The Hindu : Tamil Nadu / Chennai News : Rare spectacle delights astronomers

Online edition of India's National Newspaper
Wednesday, Jun 09, 2004

Tamil Nadu

Tamil Nadu - Chennai

Rare spectacle delights astronomers

By Lalithasai

CHENNAI, JUNE 8. Venus, the evening star, made itself evident as a small black spot slowly moving across the solar disk between 10.45 a.m. and 4.52 p.m. in Chennai.

At the B. M. Birla Planetarium in the city, all eyes were fixed on the heavens. By 10 a.m., seven telescopes and a sun spotter were positioned and ready. Expecting a good crowd to view the event, the organisers fitted solar filters in the Celestron telescope, which has an aperture of 8 inches, for safe viewing. The other telescopes projected the image of the Sun on different screens.

Much to the joy of astronomers, the principal events of the transit occurred precisely as predicted. These events, characterised as contacts, are analogous to the contacts of an annular eclipse. The transit began at 10.45 a.m. with contact I -- the instant that the planet's disk touched the Sun's rim externally. Later, it was seen as a small notch along the solar limb. Soon, at 11.04 a.m., the entire disk of the planet was seen inside the Sun at contact II. The point of second contact is an important moment when Venus appears to cross the inner edge of the Sun. Venus then seemed to elongate near the internal contact and its edge appeared deformed. This phenomenon, called the `black drop effect,' was clearly visible. Since the brightness of the Sun is diminished near the visible `edge,' astronomers call it `limb darkening'.

Contact III took place at 4.33 p.m. This is when the planet reached the opposite limb. Finally the grand transit ended with contact IV at 4.52 p.m.

Contacts I and II define the phase called ingress, while contacts III and IV define the egress phase.

The crowd that kept growing through the day also had the advantage of closed circuit televisions installed for easy viewing of the event. Students from more 50 schools in the State were involved in various projects relating to the transit of Venus. They tracked the path of Venus, every 15 minutes. Students were given access to a separate telescope to carry out their experiments with the help of their teachers.

A science teacher of Bharat Senior Secondary School, accompanying more than 100 students said, "Our students are lucky to have an opportunity to catch a glimpse of the event."

But not everyone was satisfied. Some like Gunjan, studying in class three, was disappointed with the `small' size of the planet and the black-and-white nature of the event. But five-year-old Sanskrutha was content to see just a black dot against a bright background. The event also fascinated K. P. Natarajan, an auto driver. "Since this event is occurring after 120 years, I wanted to see it." He was amazed at the astronomers' ability to forecast the celestial event so precisely.

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