Solar Eclipse : Rahu and Ketu

Rahu and Ketu, from my previous post are the astronomical points in the sky respectively called the north and south lunar nodes.

To the observer on earth, the paths of the sun and the moon appear to be two great circles projected on the celestial sphere . The sun’s path, the solar ecliptic, makes a complete revolution in one year. At the same time, the moon’s circular path is completed in about one month. Every month the moon will overtake the sun which moves more slowly. This is called new moon or in Sanskrit, amavasya. Usually the moon’s path passes above or below the sun’s path and no eclipse occurs.

But, periodically the moon overtakes the sun at the place where their paths intersect. This causes the sun or the moon to be hidden from the earth’s view and is thus called a solar or lunar eclipse.

These places of intersection are the north and south lunar nodes, or as they are referred to in Hindu mythology, Rahu and Ketu.

Therefore, in the symbolic language of mythology, Rahu and Ketu are said to “swallow up” the Sun and the Moon.

Solar Eclipse : Hindu Mythology

In Hindu mythology there is a wonderful story that describes how the gods and the demons once formed an alliance to produce a nectar that could give them immortality. This is the story of the churning of the milk-ocean and the descent of Lord Visnu as the Kurma avatara, the divine tortoise. When the nectar that was churned from this ocean was being served to the gods, a demon, disguised as a god, sat between the Sun and the Moon in an attempt to procure the nectar. When he was detected by the Sun and the Moon, Lord Visnu immediately severed his head from his body. Unfortunately, it was not fast enough, for the demon had already tasted a small quantity of the nectar and had become immortal. Ever since, this demon is said to wreak vengeance on the Sun and Moon whenever they come near. The head of this great demon is known as Rahu and his tail is known as Ketu.

In Hindu astrology Rahu and Ketu are known as two invisible planets. They are enemies of the Sun and the Moon, who at certain times of the year (during conjunction or opposition) swallow the Sun or the Moon causing either a solar or a lunar eclipse. In Sanskrit this is known as grahanam or seizing.

Solar eclipse: how it happens

A total solar eclipse occurs when the Moon passes between the Earth and the Sun during New Moon, replacing the intensely bright solar disk with a lunar silhouette. Though New Moon occurs every 29 and a half days, eclipses only occur when the angle of the Moon is such that it obscures part or all of the Sun.

This morning's eclipse was part of series 136 in the Saros cycle, which governs the recurrence of eclipses over periods of around 6,585 days.

Only the solar corona was visible during the eclipse: a much fainter white ring 600,000 miles from the Sun's surface.

Between two and five solar eclipses occur each year across the world, with each existing only along a narrow corridor in the relatively small area of the Moon's shadow.

Although they occur somewhere on Earth around every 18 months, it has been estimated that total eclipses recur at any given place only once every 370 years on average.

During this morning's eclipse, the Moon's shadow moved from west to east across the Earth at over 1500mph.

Its exceptional duration of six minutes and 39 seconds at its maximum point was a result of the Moon being near perigee – its closest position to the earth.

It is impossible for an eclipse to last more than seven minutes and 40 seconds at its maximum point, and is usually much shorter: during each millennium there are typically fewer than 10 total solar eclipses exceeding seven minutes. The last was in 1973.

The longest total solar eclipse during the 8,000-year period from 3000BC to 5000AD will occur on July 16, 2186, when "totality" will last seven minutes and 29 seconds.

Due to tidal acceleration, the orbit of the Moon around the Earth becomes approximately 3.8cm more distant each year. It is estimated that in 600 million years, the distance from the Earth to the Moon will have increased by 23,500km, meaning that total eclipses will no longer be possible.

Longest solar eclipse of the century plunges Asia into darkness

It was viewed by millions across densely populated regions of Asia and is thought to have been the most-viewed eclipse in human history. Around 30 million people watched the event in China alone.

The eclipse first appeared just before 1a.m. GMT at in India's Gulf of Khambhat just north of the metropolis of Mumbai. The shadow of the Moon then moved east across Nepal, Burma, Bangladesh, Bhutan and China before hitting the Pacific.

Astronomers travelled across the world for a rare prolonged view of the sun's corona, a white ring 600,000 miles from the sun's surface.

According to Nasa, Taregana in the eastern Indian state of Bihar was the best place to witness the event.

Shadow Chasers

The sun's disappearing act attracts so-called eclipse tourists, who travel the world to watch solar eclipses which happen between two and five times a year, though total solar eclipses are less frequent.

Solar Mystery

Scientists wants to understand why the sun's corona—gas that extends millions of miles out from the sun—is millions of degrees hotter than the sun.

The sun is just about 6,000 degrees Fahrenheit (3,300 degrees Celsius).

"Somehow energy has been put up into the corona from lower down, heating the gas, and we'd like to see how that happens," said Pasachoff, a National Geographic Society Committee for Research and Exploration grantee, will witness his 49th solar eclipse and 29th total eclipse since he began chasing the sun on October 2, 1959.

Scientists believe the coronal phenomenon has to do with the sun's magnetic field, and are looking to identify vibrating magnetic waves that move from the sun out into the corona.
Scientists can't usually see the corona from Earth because its light is fainter than the blue sky created by our atmosphere.
Furthermore, instruments attached to space satellites can't isolate all areas of the corona because the sun and the light it scatters are too bright.

The only time certain observations are possible is when the moon blocks out the sun, creating a darker sky, which highlights the coronal light around the sun.
Although the sun is about 400 times bigger than the moon, it's also about 400 times more distant. So from the ground, the moon appears to be just a little bigger than the sun.

Total Solar Eclipse Wednesday, July 22nd, 2009 : longest eclipse in the 21st century

On Wednesday, July 22nd, 2009, parts of Asia will see the earths longest total solar eclipse of the 21st century. The eclipse of the sun will be visible from within a narrow corridor in Asia and into the Pacific Ocean.

The path of the eclipse begins in India and crosses through Nepal, Bangladesh, Bhutan, and China. After leaving mainland Asia, the path crosses Japans Ryukyu Islands and curves southeast into the ocean.
A small portion of Japan will see the longest eclipse.

Compared to other solar eclipses. In fact, that will be the longest one we will have in the 21st century.

During a total solar eclipse, the moon comes between the sun and the earth and it casts a shadow on the earth. And for those people that happen to be in that small area where the shadow is, they re going to experience what we call a total solar eclipse.

And basically the moon exactly blocks out the solar disc, which is a good thing for those of us that study the outer atmosphere, because in blocking out the very, very bright solar disc, we are then able to view the outer atmosphere called the corona, which is much less brightest about a million times less bright than the disc.

So, the solar eclipse provides a rare opportunity to view the outer atmosphere, and the moon just happens to be at the exact perfect distance away from the earth that it completely blocks out just the disc of the sun.

You have to be right in the exact place where that shadow is crossing in order to experience the total solar eclipse.A larger area is covered by the penumbra, and that will provide a partial solar eclipse. But total solar eclipses are only viewed from a very small area of the earth.

Scientists warn not to view the sun with the naked eye or through binoculars or telescopes. They say failure to use filtration can result in permanent eye damage or even blindness.

Total Solar Eclipse of 1995 October 24

The three photographs of the total solar eclipse of 1995 Oct 24 were taken by Fred Espenak of NASA Goddard Space Flight Center from the small town of Dundlod, India.

The eclipse was unique for its low altitude (23 °) and short duration (40 seconds), due to the fact that the Moon was only 1.1% larger than the Sun. As a result, the limbs of the Sun and Moon were in close proximity to each other over a rather long arc at second and third contacts.

Small thing that make big difference : Electronic Appliances

Air conditioners are real energy wasters. An average room air conditioner operates at 1000 W, causing around 650 g of CO2 emissions per hour. Fans might be an alternative, otherwise use ACs sparingly and look for the most energy- efficient model

Clean AC filter every month. A dirty air filter reduces airflow. Clean filters enable the unit to cool down quickly and use less energy.

Defrost old fridges and freezers regularly. Even better is to replace them with newer models, which all have automatic defrost cycles and are generally up to twice as energy-efficient as their predecessors.

Move your fridge and freezer. Placing them next to the cooker or boiler consumes much more energy than if they were standing on their own.

According to the US Dept of Energy an electric dryer can use between 1800-5000 watts of power. You can save this energy when you air dry your clothes out.

India : Annual Mean Temperature risen by .52 Celsius

Annual mean temperature for the country as a whole has risen by .52 degree Celsius in the past 107 years since 1901, according to a data analysis by the Met department.

Environment minister Jairam Ramesh said,the concentration of green house gas (GHG) in the atmosphere was leading to global warming and that spatial pattern of trends in the mean annual temperature show significant positive (increasing) trend over most parts of the country.

However, in parts of Rajasthan, Gujarat and Bihar significant negative (decreasing) trends were observed, the minister added.

Regarding the melting of glaciers, he said as per Geological Survey of India, the majority of himalayan glaciers were receding at varying rates during the twentieth century.

The receding of glaciers may lead to reduction in their ice reserves, besides changes in the river hydrology, enhanced silt and debris production, ecological disturbances and rise in sea level, Ramesh said.