Guess what happened yesterday? It was the total solar eclipse.Do you know how it happens? Let me tell you how. A solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth, with between zero and two of them being total eclipses.[1] Total solar eclipses are nevertheless rare at any location because during each eclipse totality exists only along a narrow corridor in the relatively tiny area of the Moon's umbra.A total solar eclipse is a spectacular natural phenomenon and many people travel to remote locations to observe one. The 1999 total eclipse in Europe helped to increase public awareness of the phenomenon, as illustrated by the number of journeys made specifically to witness the 2005 annular eclipse and the 2006 total eclipse. The recent solar eclipse of January 26, 2009 was an annular eclipse (see below), while the solar eclipse of July 22, 2009 was a total solar eclipse.
In ancient times, and in some cultures today, solar eclipses have been attributed to supernatural causes. Total solar eclipses can be frightening for people who are unaware of their astronomical explanation, as the Sun seems to disappear in the middle of the day and the sky darkens in a matter of minutes.
Thursday, July 23, 2009
What is a solar eclipse?
A total solar eclipse is one of the most spectacular astronomical events. It occurs when the Moon passes between the Sun and the Earth.
For a short period of time, the Sun is completely blocked out by the Moon, when viewed from the Earth.
Day briefly turns into night, causing tempreatures to drop, birds begin to roost and many animals become confused.
For a short period of time, the Sun is completely blocked out by the Moon, when viewed from the Earth.
Day briefly turns into night, causing tempreatures to drop, birds begin to roost and many animals become confused.
Celestial mechanics
The Moon orbits our planet once every 29 and a half days. If you looked at our solar system from above the Earth, you would see that during its orbit the Moon passes between Earth and the Sun.
If you viewed the solar system from the side, however, you would see that the Moon's orbit is not always in line with the Sun and the Earth. That's why an eclipse doesn't happen every month.
Approximately once in every seven orbits the Earth, Moon, and Sun line up, and a solar eclipse occurs.
The diameter of the Sun is approximately 400 times larger than that of the Moon, but when you look at the Sun or the Moon from Earth, they appear to be the same size. This is because the Sun is almost 400 times farther away. A strange cosmic coincidence.
If you viewed the solar system from the side, however, you would see that the Moon's orbit is not always in line with the Sun and the Earth. That's why an eclipse doesn't happen every month.
Approximately once in every seven orbits the Earth, Moon, and Sun line up, and a solar eclipse occurs.
The diameter of the Sun is approximately 400 times larger than that of the Moon, but when you look at the Sun or the Moon from Earth, they appear to be the same size. This is because the Sun is almost 400 times farther away. A strange cosmic coincidence.
Shadow of the Moon
Not every solar eclipse is total. If the Sun and the Moon don't line up perfectly, then only a fraction of the Sun is covered. This is called a partial solar eclipse.
A partial solar eclipse occurs when the Moon does not cover all of the Sun.Photo by Mr J Sarkissian, CSIRO
The area experiencing a total solar eclipse will be in darkness, because the Moon blocks any sunlight from reaching the Earth.
This temporary darkness is known as the umbral shadow, and it's usually a path less than 100 kilometres in width.
Because the Moon and the Earth are always in motion, the shadow also moves. That's why a total solar eclipse doesn't last forever. In fact, viewed from any one place, it is never longer than seven minutes.
People watching in an area outside but close to the umbral shadow will see a partial solar eclipse. This is known as the penumbral shadow, and is much larger than an umbral shadow. Partial solar eclipses can last for over an hour.
A partial solar eclipse occurs when the Moon does not cover all of the Sun.Photo by Mr J Sarkissian, CSIRO
The area experiencing a total solar eclipse will be in darkness, because the Moon blocks any sunlight from reaching the Earth.
This temporary darkness is known as the umbral shadow, and it's usually a path less than 100 kilometres in width.
Because the Moon and the Earth are always in motion, the shadow also moves. That's why a total solar eclipse doesn't last forever. In fact, viewed from any one place, it is never longer than seven minutes.
People watching in an area outside but close to the umbral shadow will see a partial solar eclipse. This is known as the penumbral shadow, and is much larger than an umbral shadow. Partial solar eclipses can last for over an hour.
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