Types of Solar Eclipse

 

There are four different types of solar eclipse, namely Partial eclipse, Annular eclipse, Total Eclipse and Hybrid Eclipse.

 

Partial Eclipse

 

A partial solar eclipse occurs when only part of the Sun is covered by the Moon which appears to take a ďbiteĒ out of the Sun. This is the general appearance of a partial eclipse.

 

Partial eclipses occur when the umbral shadow of the Moon misses the Earth and only its penumbral shadow falls on the Earthís surface. Refer to Figure 1B. In this case, the umbral shadow will either pass over the north or south poles of the Earth. Note that the area of the Earth that falls within the area of the penumbra will experience the partial eclipse.

Figure 1B

Within the penumbral area, the Sun is partly covered and there is dim light of varying degrees. Observers within the area of the penumbra and close to the umbra will see the Sun almost covered while observers at the edge of the penumbra will see a crescent Sun.

 

A partial eclipse begins occurring with the onset of the First Contact and the onset of the Third Contact of a total eclipse where it looks like the crescent Sun as in the picture above. A partial eclipse also always accompanies a total eclipse, falling over a larger area of the Earthís surface. This is due to the penumbra always surrounding the umbra.

 

 

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Observers outside the path of totality or annularity during a total or annular eclipse may also experience a partial eclipse.


Partial Solar Eclipse. In courtesy of http://www.hartrao.ac.za/eclipse2002/

 

 

 

 

 

Annular Eclipse

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An annular(annular comes from the Latin annulus or ring) eclipse occurs when the Sunís center is covered by the moon , leaving its edges left uncovered, producing a ring (or annulus) of the Sun around its edges.

 

Annular eclipses occur when the moon appears smaller than the Sun.

 

 

 

1994 eclipse animation courtesy of Fred Espenak

and http://www.MrEclipse.com

 

 

Annular Eclipse

 

The Moon and its elliptical orbit is further from the Earth and its umbra is too short to reach the Earth. But the moon is located exactly in front of the Sun. This enables the umbral area below to observe the centre of the Sun covered, leaving a ring (an annulus) of the Sun visible around the edges of the moon. Observers in the penumbral area witness a normal partial eclipse instead.

 

In an annular eclipse, you don't get to see any of the "special effects" of a total eclipse, such as the corona, or diamond ring effect. The thin sliver peeking around the moon is far too bright to allow this.

 

 

 

 

Total Eclipse

 

A total solar eclipse takes place when the Sun becomes completely covered by the moon.

 

 

 

In a total solar eclipse, the moon, in its elliptical orbit, passes between the Sun and the Earth at a point where it is also quite close to the Earth. As this occurs, a shadow is cast upon the Earthís surface. The umbral part of the moonís shadow is the area where the Sun is completely blocked off by the moon. The moon appears close enough to the Earth during a total eclipse and observers within the umbra will witness a total eclipse of the Sun where the Sunís face is totally blocked off by the moon.

 

 

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Total Solar Eclipses

 



Total Solar Eclipse

In courtesy of http://www.hartrao.ac.za/eclipse2002/

 

  

 

 

Hybrid Eclipse

 

The Hybrid eclipse is a fairly rare event. A hybrid, or annular or total eclipse, is one which is seen as annular by observers in one part of the Earth, and at the same time, is seen as a total eclipse by others in another part of the Earth. The diagrams below show how a hybrid eclipse is formed.

 

 

 

 

The moon is merely far enough from the Earth but the umbra cannot reach the sides of the Earth. As eclipse takes place, the western part of the Earth will see an annular eclipse. Observers in the outer parts of the eclipse track (outlined in green) will witness an annular eclipse.

 

The eclipse is annular when it begins and ends. However, as a result of the curvature of the Earthís surface, the apparent size of the moon increases in size till it is just enough to produce a total eclipse.

 

 

 

 

As the eclipse path continues to move on, the umbra does not need to travel far to reach the Earth, and is also just long enough to reach the center which faces the moon directly. Observers in the outlined blue area will witness a total eclipse.

 

The eclipse remains a total eclipse till the end of the eclipse when it will develop into an annular eclipse again.

 

Hybrid eclipses always have short duration of the annular and total eclipse phases.

 

 

Deciding Factors for the type of Solar Eclipse to Occur

 

The type of eclipse that does occur depends on several things. First, if the eclipse happens when the sun is further from the node, it is more likely that the eclipse will be a partial one. In this type of eclipse, the dark umbra passes above the North Pole or below the South Pole, never touching the earth. All we ever see is part of the sun covered.

Diagram: Earth & Moon orbits

There's another variable, though. Remember that the orbits of the earth and moon are not perfect circles, but rather ellipses. Note that in the diagram above (again wildly out of scale), the earth is sometimes closer to the sun and sometimes further. The same is true for the moon--sometimes it's closer to the earth and sometimes it's further. See the table below:

 

 

Close Distance

Far Distance

 Sun

147,101,455 km

152,098,155 km

 Moon

356,749 km

406,282 km

 

As you can see, both the sun and the moon change their distances quite significantly. The moon changes by about 14 per cent, and we vary our distance to the sun by about 3 per cent. Because of this, the sun and moon look bigger sometimes and smaller at other times. If we're far from the sun so that it looks smaller, and close to the moon so it looks bigger, the moon will be able to cover over the entire face of the sun as seen from earth, and we'll see a total eclipse. If the opposite is true and we're close to the sun and far from the moon, the moon will appear too small to cover the face of the sun, refer to table 1A below.

In this case, it's like trying to cover a penny with a dime. You would see a ring of copper penny sticking out on all sides of the dime. This happens with the sun and moon. You see a ring of the sun shining around the edges of the moon --- annular eclipse.

 

Position of Earth

Position of Moon

Type of Solar Eclipse

Aphelion

(maximum distance from Sun) Sun image minimum

Perigee

(minimum distance from Earth)Moonís image maximum

Total

Perihelion

(minimum distance from Sun) Sunís image maximum

Apogee

(maximum distance from Earth) Moonís image minimum

Annular

Table 1A. Orbital conditions of Earth and Moon for solar eclipses.