ECLIPSES OF SUN
Data from Wikipedia and NASA (C)
A Sun
eclipse happens when the Moon passes between the Earth and the Sun and so obscures totally or
partially the vision of the Sun from our planet. This situation can only happen
in the phase of new Moon, when the Moon and the Sun are in conjunction as seen from
the Earth. The total eclipses are rare events, that
happen only in some part of the globe in how much the totality verificates when the lunar shadow touches the earth surface.
TYPE OF ECLIPSES
They
exist 4 type of solar eclipses :
Total,
happens when the Sun is completely darkened from the Moon. The disc of the Moon covers that one of the Sun, with consequent
strongly decrease of brightness; it can see only the crown that
encircles our star. The line of totality on the Earth is a tightened wraps said
path and only who is found in its inside will see the Sun totally eclipsed.
Annular,
happens when the Sun and the Moon are aligned but the lunar disc is smaller
than that solar one for via of the Moon near to the apogee or of the Earth to
the perihelion. In such eclipses the Sun appears like an
luminous ring that encircles the lunar disc.
Hybrid,
happens when the eclipse is total and annular to second of the point of earth
observation. They are extremely rare.
Partial,
it happens when the Moon and the Sun aren’t perfectly aligned and only a part
of the Sun comes darkened. This phenomenon generally is seen from a great part
of the earth’s surface in the outskirtses of the
totality zones or annlarity. Moreover some eclipses
are exclusively partial when only a part of the lunar shadow intersects the earth
surface.
The
distance between Earth and Sun is approximately 400 times the Earth-Moon
distance; the diameter of the Sun is approximately 400 times that lunar one.
This analogy of relationships provokes that the Sun and the Moon as seen from
the Earth have approximately the same angular diameter, half degree.
Since
the orbit of the Moon around to the Earth is a elipse, therefore like that one of the Earth regarding the
Sun, the apparent dimensions of Moon and Sun varies continuously. The magnitude
of a eclipse is the relationship between the dimension
appearing of the Moon and that one of the Sun during a eclipse. If the Moon is
near the perigee its disc will appear enough large to cover the Sun and its photosfera, in such case the magnitude is greater of 1 and
the eclipse is total. Viceversa if the Moon is near
the apogee the eclipse will be annular and the magnitude inferior to
Analogous
in the periods in which the Earth it near the aphelion will take place more
easy a total eclipse, if it near then perihelion an annular.
La definizione “eclisse centrale” spesso è usata
genericamente per totale, anulare o ibrida. Tuttavia non è corretto, poiché
l’eclisse è centrale solo quando la linea dell’ombra tocca la
superficie terrestre. E’ possibile, ma raro, che una
parte dell’ombra intersechi
The
definition "central eclipse" is used generically for total, annular
or hybrid. However it is not corrected, since the eclipse is cental only when the line of the shadow touches the earth
surface. It is possible, but rare, that a part of the shadow intersects the
Earth giving place to a annular eclipse or total and
that the line is not centrals (total eclipse or non central annular).
The same
term solar eclipse would be wrong in how much the passage of the lunar disc on
that solar one is a occultation; a true eclipse is had when a body passes in
the shadow of an other, typical the case of the Moon eclipses.
PREDICTIONS
The
outline, not in scale, shows an alignment Sun-Earth-Moon during a solar
eclipse. The black region to right of the Moon is its shadow, place in which
the Sun is completely darkened. The small area that touches the Earth is where
the eclipse is seen like total. The blue zone of the image that encircles the
shadow is said penumbra, place in which the Sun is covered partially and it
generates therefore partial eclipses.
The plan
of the lunar orbit is tilted regarding that earthling of the ecliptic of 5°.
Because of that in the moment of the new Moon the Moon usually passes over or
under the Sun. An eclipse can only happen when the new Moon is close to one of
the points (sayings nodes) in which the lunar orbit intersects that earthling,
the ecliptic.
As said
over the lunar orbit is elliptic and the distance of the Moon from we varies of approximately 6% around to the medium value.
Adding to this effect the variations of the earth orbit is clear that
approximately 60% of the central eclipses are annular.
The
lunar orbit intersects the ecliptic in the two nodes distant between they 180°. The new Moon happens close to the nodes in two
periods distant between they approximately 6 months,
and therefore in these periods there will be at least a solar eclipse.
Sometimes the new Moon happens enough near to a node in two consecutive months.
This means that in that year there will be at least 2 solar eclipses, with a
maximum of 5. However some of they will be only partial since the shadow passes
over or under the earth poles.
During a
central eclipse the lunar shadow (or the antishadow
in the cases of annular eclipse) moves quickly from the west to east long the
Earth. The Earth same rotates from the west to east but the shadow moves more
and more fastly so that it seems that the eclipse is
moved from the west to east on the earth surface.
The amplitude
of path of totality varied in relation to the relative diameters of Sun and
Moon. In the more favorable conditions, when a total
eclipse happens very close to the perigee, the totality can extend for
The
solar total eclipses are rare events and although happen in average every 18
months esteem that in a point whichever of the Earth happen every 370 years in
average. The duration of eclipse in a place whichever is a few minutes since
the lunar shadow move to the speed of
If one
knows the date and the hour of a solar eclipse it is possible to foretell the
successive ones by means of the use of the cycles. The most famous are the
Saros and the Inex. The Saros, the most accurate, durates 6585,3 days, a little less
than 18 years, and that means that after this period the eclipses are repeated
practically in identical way. The more remarkable difference is a movement of
120° in longitude and a few in latitude. A cycle of
Saros always begins with a partial eclipse in the polar
regions then traslates on the globe with an
series of totals and annular eclipses and ends in the opposite polar region. A Saros durates from 1226 to 1550 years
and with 69-87 eclipse, of which 40-60 centrals.
Because
of the tidial forces the lunar orbit
goes away of approximately
OBSERVATIONS
The
direct observation of the Sun, also only for little second, cause permanent
damn to the hairnet of the eyes causing also the blindness.
In
normal conditions the Sun is therefore luminous that isn’t the tendency to
watch it. However during an eclipse, when great part of it is covering, is
easier to watch it a long time. Ill-fatedly also in this situation they are serious
risks, much more if binoculars or telescopes are used. They are absolutely
necessary special glances or protections for the sight; the better way for its
observation is the projection on a sheet.
Only
exception is an observation during the short moments of totality since the
solar brightness is so attenuated not to damage the eyes.
TECHNICAL NOTES
Said γ (gamma) the minimal distance from the axis
of the shadow of the Moon to the center of the Earth,
in unit of earth land equatorial radius
·
if
γ > 0 the
axis passes to north of the center of the Earth and it
is favorite for the observation the hemisphere north
·
if
γ < 0 the
axis passes to south of the center of the Earth and it
is favorite for the observation the hemisphere south
·
If |γ| < 0,9972
the eclipse is central, that is exists a line of central eclipse on the surface
of the Earth
Saying u the radius of the cone of shadow of
the Moon in the fundamental plan, that it is the plan that passes for the center of the Earth and is perpendicular to the axis of the
shadow of the Moon
·
if
u < 0 the eclipse is total
·
if
u > 0,0047 the eclipse is annuar
·
if
0 < u < 0,0047 the eclipse is annular or total-annular
In this
last case saying ω = 0,00464√(1-γ²)
·
if
u > ω the
eclipse is annular
·
if
u < ω the
eclipse is annular-total
The radius
of the cone of shadow of the Moon in the fundamental plan is u+0,5460
·
if
|γ| is between 0,9972
and 1,5432+u the eclipse is non centrla is always
partial
·
if
|γ| is between
0,9972 and
·
if
0,9972 < |γ|
< 0,9972+|u| the eclipse is non central total or annular; eclipse of this
type is only one, on
·
if
|γ| > 1,5432+u there
aren’t visible eclipses from the earth surface
In the
case of partial eclipses the maximum magnitude in the better place of visibility
on the Earth, that it is more close to the axis of the shadow is
1,5433+u-|γ|
------------
0,5421+2u
CURIOSITY
As
saying the maximum possible number of eclipse in a year is 7:
5 solar
+ 2 lunar, on 1805,1935,2206 (4 on 5 are partial)
4 solar + 3 lunar
3 solar + 4 lunar
2 solar +
5 lunar on 1879, 2132
In some
cases all the eclipses in a year can be partial, 2 on
The
maximum number of solar eclipses in a year is 2, on 1973
The
maximum number of annular eclipses in a year is 2
The
maximum number of solar total+annular eclipses in a
year is 3, 1489, 1666, 3192
Usually
the hybrid eclipses are totals in the beginning moments, then they annular and
finally they return totals. The eclipse of
2
consecutive eclipses cannot be both only total
2 consecutive
eclipses can be both hybrid, ex. 23/12/1908 e 7/06/1909
The
smallest partial eclipse of Sun of this century will have magnitude 0,005, on
24/10/2098. A more small will happen on 23/08/2883
with magnitude 0.001.
Between
the year 0 to 4000
If 2
successive new moon give place to a solar eclipses in
nearly all the cases they are both partial and visible from opposite
hemispheres.
The
intersection of the cone of shadow with the fundamental plan creates a small
circumference whose the maximum is 3% of the Earth. In the case of the penumbra
it is between the 53 and 58%.
Between
the year 0 and 4000
In our
century only 11 eclipses will exceed 5 minuteren, the
longest on
The
maximum duration of a annular eclipse is 12m30s.
Between
the year 0 and 3000
Two
successive solar eclipses generally are separated from 6 lunations,
much more rarely from 5 or less. When they be distant only 1 lunation the
phenomenon calls Duo. In 20° and 21° century there are 31 Duos. Last in the 2000 (
The christmas eclipses are much rare,
in our single millenium 13, of which 4 totals, 3 annulars and 6 partial ones, the next one in 2038.
Rare also the eclipses on 29 February, from year 0 to 3000d.C. only the
8 cases, the next one in 2044.
The
eclipse with the longest line than totality exceeds the
TYPE OF ECLIPSES
TYPE I
The
entire lunar penumbra passes on the Earth, exists therefore a centrality line.
The eclipse can be annular, total or hybrid.
In all
the points of the curve D’UM' the eclipse begins at daybreak, an observer sees
all the eclipse. In all the points of the curve D’QM' the eclipse it ends at daybreak,
an observer will not see nothing. In all the points of the curve D’G'M' the
maximum of the eclisse happens at daybreak. In the
region D’G'M'V the Sun rises eclipsed and it will look the maximum of eclisse and the end. In the region D’QM' G' the Sun rises
eclipsed, but the end will be only the end. In all the points of the curve L’VR'
the eclipe ends to the sunset, an observer sees
however all the eclipse. In all the points of the curve L’TR' the eclipe begins to the sunset, an observer does not see
nothing. In all the points of the curve L’H'R' the maximum happens to the
sunset. In the region L’VR'H' the o Sun set eclipsed, will look the beginning
and the maximum. In the region L’H'R'T the o Sun set eclipsed, will look only the
beginning of the eclipse. In the region L’VR'M'U all the eclisse
will be visible, from the first one to the last contact. The line G'H' is the
totality line. In the places on the curves D’L’ and M'R' the Moon touches the Sun, the eclipse is partial with magnitudine
0,000.
Are of type
I the eclipses on
TYPE II
Only a part of the lunar penumbra passes over the Earth, therefore a
centrality line exists and the eclipse it can be total, annular or hybrid.
The
visibility conditions are the same ones of type I, but the curves that delimit
rising and the sunset of the Sun aren’t separated but they form an 8, the curve
M'QWVR'TWU. On arc WUM' the eclipse begins to the dawn. In region WQM'U the Sun
rises eclipsed. On arc WTR' the eclipse begins to the sunset. In area WTR' V
the sun sets eclipsed. In area WUM' R'V the eclipse is visible entire. The
curve M'G'H'R' is the line of "maximum eclipse on the horizon". The
curve G'UVH' is the totality line.
Are of
type II the eclipses on 1° august 2008,
TYPE III
Less of
the half of the lunar penumbra passes on the Earth and the cone of shadow or
its extension does not touch it. The eclipse is partial.
The
visibility regions are same of type II, except that does not exist
the centrality line. The maximum magnitude of the eclipse happens in Y' not far
away from W. Y' is in fact the point on the earth surface more near to the axis
of the shadow.
Are of
type III the eclipses on
The
eclipses type I, II e III are the most frequent.
TIPO IV
The
entire lunar penumbra passes on the Earth, however the limit north (or south)
of the penumbra touches the Earth from the same part regarding the meridian centers them (DL regarding NS in figure).
In the
point D’ the eclipse begins at daybreak, in L’ ends at daybreak. The limit
north D’L’ often is an arc much small. The curves of beginning and ending with
the Sun on the horizon are separated, but one of they is distorted and forms an
8. On the arc D’UM' the eclipse begins at daybreak. On the arc D’QM' the eclipse
ends at daybreak. On the curve R' VW the eclipse ends to the sunset of the Sun.
On the curve WaL' the eclipse ends at daybreak. On the
curve R'TW the eclipse begins to the sunset. On the curve WbL'
the eclipse begins at daybreak. In the area WaL'b the
Sun rises eclipsed. In area WVRT the Sun set eclipsed. The limit south of
the eclipse is the curve M'R', the centrality line the curve G' H', and there
are the classic 2 curves of "maximum on the horizon": on D’G'M' the
maximum it happens at daybreak, on W'H'R' to the sunset. The area WaL'b can be also on the first curve, neighbor
to D’, or in M' or R', but not on two curves at the same time.
In some
cases 2 consecutive eclipses are of type IV.
In the
first figure saying ψ the angle between NS and GH, will be
an eclipse of type IV if
0,997 sin ψ < |γ| + u < 0,997
It is of
type IV the eclipse on
TYPE V
This
type of eclipse happens when the central line touches the Earth from the same
part regarding the central meridian.
In this
case the central line begins and ends at daybreak. G and H are both in area
NMS. Obviously G and H could be also in area NRS and in this case the central line
begins and ends to the sunset of the sun. In any case the W node is not between
G' and H'. In no case the eclipse will be visible to
So that happens
a eclisse of type V must be
taken place
0,997
sin ψ < |γ| < 0,997 with ψ like up.
Will be
of type V the eclipses on
TYPE VI
This
type of eclipse happens when only a small part of the cone of penumbra of the
Moon touches the Earth.
In such
situation the curve of the limit north (or south) begins or ends at daybreak
(or to the sunset). In no case the eclipse he is visible to
So that happens
a eclisse of type VI must be
taken place
0,997
sin ψ < |γ| - L < 0,997 with ψ like up.
The
eclipse will be always partial with the maximum magnitude 0,25
and visible in the polar regions.
Will be
of type VI the eclipses on
TYPE VII
This
type of eclipse happens when only a part of the cone of shadow of the Moon
touches the Earth. The eclipses areannular or total
(not central)
The area
in which the eclipse is visible is a small semicircle. The visibility
conditions are like in type III. The totality region is delimited from the
curve of "maximum on the horizon". In the case in figure an observer
in the small semicircle can see the beginning of the partial phase and the
totality, but not the end of the eclipse. If the small semicircle it were on
the curve M'W it would see instead the maximum and the end but not the
beginning. If the small semicircle it coincided with the W point happens a
strange event: the eclipse it begins with the Sun under the horizon, it can see
the phase of maximum, and the end of the eclipse happens with the Sun under the
horizon, like
An
eclipse of type VII was on il
NOTES ON THE SOLAR ECLIPSES
The
medium frequency of a total eclipse of Sun for a data point on the Earth is of
375 years.
The
medium frequency of an annular eclipse of Sun for a data a point on the Earth
is of 224 years.
The
medium frequency of a total or annular eclipse of Sun for a data point on the
Earth is of 140 years.
There
are nations in which a total eclipse does not happen from centuries:
·
Tahiti,
·
Seychelles,
·
Bermuda,
·
Israele,
·
Vaticano,
·
Malta,
·
Madeira,
And many
will have to wait for centuries:
·
Falkland,
·
Danimarca,
·
Madeira,
·
Tahiti,
Considering
the period from 1401 to 3000 it discovers that there are places in which in
less than 7 years happen 3 total solar eclipses:
mare di Java,
Messico, 1796,1799,1803
Filippine, 1814,1817,1821
Oceano Indiano, 1849,1854,1856
Oceano Indiano, 2194,2197,2201
In a
place of the pacific Ocean from the 2447 will be
looked 4 total eclipses in only 4 year!
But the
record is 5 total eclipses in 32 years.
During a
solar eclipse often some planets are looked near the Sun; from 1900 to
Rare also the occultation of planet from part of the eclipsed Sun, only
one from year 0 to 3000, on
If we
consider the duration of an eclipse from the moment of the first contact to the
moment of the last contact, independently from the totality, annularity or
partiality, the time can exceed the 4 hours. The longer event happened on
The
wider path of totality: in the arc of 3 millenia,
there are 14 cases in which it is wider than
The
wider path of annularity, always from year 0 to 3000: 13 cases in which it is
wider than
In rare cases they can be
many successive eclipses of which no partial one, example, 6 eclipses, from the
In 348
they have been quite 7 consecutive eclipses and from the