Last update: November 07 2006, 11:50 PM
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Sorsogon town Ďbest spotí to observe cosmic event

November 07, 2006

GUBAT, SORSOGON -- A group of astronomers will troop to this resort town on Nov. 9 to document what they described as the cosmic event of the year -- the transit of Mercury or its passing in front of the sun.

The phenomenon could be observed worldwide, but there are only several areas in the Philippines where the maximum transit will be visible, according to Rochelle Derilo, education committee chair of the Philippine Astronomical Society (PAS).

Maximum transit occurs when Mercury, the planet in the solar system nearest the sun, is at the midpoint of its path across the sun.

Derilo said the phenomenon could be observed anywhere in the Philippines, but the maximum transit could be seen only if one was observing it from the eastern side of the Philippine archipelago.

She said this town is the best spot in Luzon because it is the easternmost and the shore faces the spot where the sun will rise.

Derilo, whose parents are both from Sorsogon province, said the transit would start at 3:12:28 a.m. for the first contact; 3:14:20 a.m., 2nd contact; 5:42:09 a.m., maximum transit; 08:08:49 a.m., 3rd contact, and 08:10:42 a.m., 4th contact.

Earthís point of view

During the transit, the sun and Mercury will look like disks from Earthís point of view, according to Derilo.

The first contact takes place when both disks touch each other; the second contact is when the other side of Mercuryís disk touches the sun -- thus, Mercury is completely in the sunís disk.

In the third contact, Mercury starts to exit the sunís disk. The fourth contact is the point in which Mercury will have completely come out of the sunís disk.

Only two planets -- Mercury and Venus -- transit the sun, according to astronomers. The transiting comes in pairs.

A pair of Venus transits is eight years apart, while that of Mercury is three years apart.

The last Mercury transit occurred on May 7, 2003, and the next will be on May 9, 2016, Derilo said.

Transits are important because they help in refining a planetís orbital elements, determine if the planet is being ďtuggedĒ by small rocky bodies within its orbit, or if there are discrepancies in the gravitational pull from the sun.

Timing equipment

Derilo said the PAS would set up an observation post in Gubat for the event using sophisticated timing equipment.

The astronomers will use white light filter, which is used to observe the photosphere of the sun, and hydrogen-alpha filter. The second filter blocks all wavelengths except hydrogen-alpha which is seen from the sunís chromosphere.

Although Mercury is small (9.95 seconds of an arc), it will be noticeable because the dark spot on the sunís disk will be very sharp as the planet does not have atmosphere to blur its edges, according to Derilo.

Doís and doníts

She, however, cautioned the public against looking at the sun directly without using appropriate filters.

She recommended Neutral Density 5 aluminized Mylar filters for those who will observe with the naked eye, and higher neutral density numbers for those who would be using telescopes and other optical devices.

Using sunglasses, smoked glass, X-ray negatives or diskettes to observe the sun, especially through an optical instrument, could damage the eyeís retina because of the infrared and ultraviolet rays, she said.

For those who want to observe the transit but lack the necessary filters, the PAS suggested that the safest way was to project the sun onto a piece of white paper.

Aside from Gubat, areas in the country where the phenomenon can be best observed are the cities of Sorsogon, Tacloban and Surigao because of their eastern location.

Viewers in these areas will have a fuller view of the transit than those who are in Manila, Derilo said.

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