astronomy new

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AstronomyUniverseOur Universe contains millions and millions of Galaxies. Each Galaxy contains millions andmillions of stars. Exact number of Galaxies and stars are not known to the mankind. Thedistances between stars and galaxies are very huge. Polar Star is 20 light years* away. In

other words light takes 20 years to reach to us from the Polar star. To see the Polar Star of year 2005 we will have to wait till the year 2025 on Earth. Nearest Star from Earth “Alpha-Proxima Centuri is 4.2 light years away from us. Broadly Stars are classified in four types.Small, Medium, Big and twin star systems. Our Sun is a medium star. Our Solar system isvery small as compared to the size of the Universe. Earth is close to the Sun than Planets of the Solar system except Mercury and Venus. Light takes 8 minutes to reach from Sun toearth.

* Light year = Distance travelled by light in one year.Speed of Light = 3,00,000 km per second.Therefore, Light year = 9462.9 billion km.

The big bang theory

HUGE MASS EXPLOSION

Fig 1.1 Fig 1.2

According to the big bang theory Universe started with an explosion which led to the formation of millions of galaxies Look at the Fig.1.1 which explains that all the matter in the Universe was one anddue to tremendous heat an explosion took place (Fig.2) which resulted into formation of Galaxies &Stars. All these galaxies are expanding and the universe is also expanding.Formation of Solar System

Fig. 1.3

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H e a v i e r M e t a ls

F O R M A T IO N O F P L A N E T S



Sun is a medium star in our galaxy. As for the origin of planets it is believed that the cloud of gas & dustcondensed from the spinning star, i.e. Sun. This cloud & dust contained heavier metals Fig.1.3. Due tocentrifugal force they moved away from Sun. It resulted in cooling down of this mass & formation of various planets & other heavenly bodies. Some astronomers are also of the opinion that when Suncooled down the planets were formed then.

The Solar SystemThe Solar system consists of Sun and other members of the family consisting of several celestial bodieswhich revolve around it. The Sun is at the center of this system and has light of its own. There are ninemajor planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, minor planetsor asteroids, meteoroids, comets, interplanetary gas, dust and solar wind. Some planets also havenatural satellites, which revolve around the respective planets and in many ways mimic the solar systemon a smaller scale.

Fig. 1.4

Out of the nine major planets, six were known. These in order of increasing distance from the Sun areMercury, Venus, Earth, Mars, Jupiter and Saturn. With advance in Astronomy, three new additions havebeen, made in recent years. These are Uranus, Neptune and Pluto. Sir William Herschel discoveredUranus, also called Herschel, in 1781. The German astronomers Johann Galle and Heinrich d’Arrestdiscovered Neptune in 1846. US astronomer Clyde Tombough discovered Pluto in 1930.

Ptolemy gave the theory that the Earth lay at the center of the universe and all the celestial objects

revolve around it. However Aryabhatta (born in 476 A.D.) stated that the Earth is in orbit around theSun. Historically the credit for this discovery has been given to Copernicus (1543 A.D.) The view of Copernicus was greeted with intense hostility by the Roman Catholic Church. Galileo, the notedastronomer was put in jail in the last few years of his life & was made to drink poison for supportingCopernicus that the Earth revolves round the Sun. Over a period of time, it got the acceptance itdeserved.

There were various theories with regard to planetary orbits also. But their accurate nature was explainedby Johannes Kepler in 17th century and is valid even till today. The planetary orbits are not in the sameplane and are elliptical in shape. The orbit of the Earth makes the ecliptic plane whereas all other planets are slightly inclined to the ecliptic.

The solar system can be divided into two types of planets based on their size and comparativedistances from the sun. The inner solar system consists of planets Mercury, Venus, Earth and Mars.

They are small in size and comparatively closer to the Sun. Jupiter, Saturn, Uranus, Neptune and Plutofall under the outer solar system. The large sizes, vast distances from the Sun and their ring systemscharacterize them. The only exception in size is Pluto, which is a small, cold and icy planet. Pluto’s

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N e p t u n e

P l a n e t s a n d t h e i r O r b i t s

S u n

M e r c u r y

V e n u s

E a r t h

M a r sJ u p i t e r

U r a n u s

S a t u r n

P l u t o



perihelion lies inside the orbit of Neptune and thus it is considered to be an escaped satellite of Neptune. In recent years Charon was also discovered Charon & Pluto form a two-object system & it issatellite of Pluto.

All planets revolve around the Sun and also rotate on their axes. The direction of their revolution androtation is identical. The period of rotation of planets on their axes and the period of revolution aroundthe Sun for the nine planets are :

Planets Period of rotation on its axes Period of revolution around the Sun

Mercury 59 days 88 daysVenus 243 days 225 daysEarth 23.9 days 365.25 daysMars 24.6 hours 687 daysJupiter 9.9 hours 12 yearsSaturn 10.2 hours 30yearsUranus 17.2 hours 84 yearsNeptune 18.4 hours 165 yearsPluto 6.4 days 248 years

Geocentric and Heliocentric systemHindu astrology is known as pratyaksha shastra which means what is visible or the apparent movement of planets.

In geocentric observations the Earth is taken as the center of the universe. Though we know that Earth is movinglike other planets around the Sun, yet for the purpose of ease of understanding Astrology we continue to follow the

ancient geocentric system of observations.

In heliocentric observations the Sun is at the center of the universe and other planets revolve round it. Astronomers are more interested in heliocentric observations.

In other words it has been so described because of geocentric observations, astronomically andpredictable results, astrologically.

Inner and Outer Planets

Mercury and Venus are situated between the Earth and the Sun and are called the minor, interior or inferior planets. Mars, Jupiter, Saturn, Uranus Neptune and Pluto are situated far away from the Earth.Their orbits are outside the Earth’s orbit. They are called outer, or superior planets are different from theinner and outer solar system explained earlier. It should be clearly understood that Venus & Mercury arecalled as inferior planets because of their smaller distance from the Sun than the outer planets & not for any other reason. Similarly the outer planets are said to be superior because of their large distancesfrom the Sun.

The SunIt is the prominent body of our solar system and life giver being the only luminary in the true sense. It isthe star around which the Earth and other members of the solar system revolve. Sun is having a meandistance of 1,49,600,000 kilometers from the Earth and is nearly 8 light minutes away which means thatthe time taken for the light of Sun to reach the Earth is about 8 minutes. The mean angular diameter of the Sun’s disc is 31’59.3” of the arc. Major constituent of Sun is Hydrogen. The brilliance of Sun is dueto millions of nuclear fusion reactions taking place daily. In a fusion reaction two Hydrogen atoms fuse

together which results single Helium atom giving rise to tremendous energy in terms of heat and light.

Hydrogen* + Hydrogen = Helium ** + Energy

*Constituents of Hydrogen: One Proton and One Electron** Constituents of Helium: Two Protons and two Electrons

Natural Satellites Any natural body that orbits around a planet is natural satellite of that planet. In our solar system thereare 60 known satellites of varying size. The seven largest are Earth’s Moon, Jupiter’s Io, Europa,Ganymede and Callisto, Saturn’s Titan and Naptune’s Triton. Some of the large satellites likeGanymede and Titan are bigger than Mercury. There are groups of small satellites in huge quantities,which form the ring system of large planets of the outer solar system. Jupiter, Saturn, Uranus andNeptune have prominent rings but the rings Saturn are most elaborate. Our closest neighbour Mars has

two small satellites called Phobos and Deimos. Since they are not spherical in shape they are believedto be captured asteroids. Pluto’s only satellite called Charon is nearly equal to Pluto’s size.

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Comets A Comet is a member of the solar system and visits it at regular intervals. Comets are formed of ball of ice, dust and frozen gases in definite and highly elliptical and eccentric orbits around the Sun. Therepath are so elliptical and eccentric that many of the comets come near to the nearest planet Mercuryand go out from the Puto’s orbit and come back to the same position after fixed time intervals. The ballof the comet is called its nucleus and the tail, which always points away from the Sun, is the halo of gasand dust continuously swept away by the solar wind. When a comet, in its orbit, comes near to the Sun

then the frozen ice and gas begin to vaporize and the comet becomes visible and the tails becomeslonger. The Comet looses some of its mass in the space when it approaches the Sun. Thus the greater periodicity of a comet to become visible leads to its destruction.

There are a number of comets in the solar system and the exact figure is not known. A famous comet isthe Halley’s comet, which visits our inner solar system after every 76 years. The Halley discovered it in1696. First recorded in 240 B.C. it is visible to the naked eye and orbits in the opposite direction to theorbit of the planets. It was last observed in 1986 and its next return is expected in the year 2061.

AsteroidsThe belt of minor planets located mainly between the orbits of Mars and Jupiter are called asteroids.There are an estimated 100 million asteroids in the main belt. Out of these there are over 1 million whichhave a diameter of over 1-kilometer each. There are certain asteroids, which travel in the same orbit asJupiter or Saturn and are 60 degree ahead or 60 degree behind as seen from the Sun. These are called

Trojan minor planets or asteroids. These are the fragments of once bigger minor planets. The orbits of asteroids are in the gravitational influence of Jupiter. Orbits of some the asteroids are highly elliptical sothat they sometime come in between the orbits of Earth and Mars.

Meteoroid, Meteor and Meteorite

Meteoroid: Meteoroids are small bodies in the interplanetary space, which are too small to be studiedindividually or separately. A meteoroid is a mass of rock, fragments of planets, or dust particles floatingin the space.

Meteor: When a meteoroid comes in contact with the atmosphere then due to the gravitational force itsvelocity increase and friction with the atmosphere creates enough heat to burn the meteor. A shootingstar or a streak of light seen at night is nothing but a meteoroid, which is burning due to the friction withthe atmosphere of Earth and is, called a meteor.

Meteorite: The remnants of meteors, which do not completely burn out in the atmosphere of the Earthand hit the Earth’s surface, are called meteorites. A meteorite has a velocity of 74 km/second when ithits the Earth. They are basically those asteroids, which have highly eccentric orbits during their journeythey cross the orbit of the Earth, get into the atmosphere and get attracted towards the Earth due togravitational force of the Earth.

Solar WindThe small particles in the interplanetary space consisting of protons, electrons, atoms, molecules andions get ionized due to Sun’s ultra violet radiation which is ejected from the Sun. This radiation canreach distance of over 100 astronomical units in the interplanetary space. The effect of solar wind isvisible to the naked eye when we see the tail of comet. Solar wind sweeps the nucleus giving rise to thetwin tails of the comet which always align away from the Sun.

The EarthThis planet is third in distance from the Sun and the only planet, which has life (as known by themankind). Radioscopic studies on oldest crystal rocks reveal that the age of Earth could be 3.8 billionyears. But there is evidence that the Earth must have formed along with other members of the solar system 4.6 billion years ago. The Earth is 12,756 kilometers in diameter at the equator and 12,714kilometers as measured through the poles. Distance around the earth’s equator is 40,074 km & thataround poles is 39,942 km. Weight of the earth is 5,976,000,000,000,000,000,000 tons & its volume is1,080,000,000,000 cubic km. It is the largest planet of the inner solar system and has a mean density of 5,520 Kg/m. it rotates on its axis in about 23 hours and 56 minutes. The Earth takes about 365.25 daysto complete on orbit around the Sun and has one natural satellite called the Moon.

The Earth rotates or spins on its axis from west to east. Therefore all heavenly bodies appear to bemoving or orbiting the Earth from east to west. The Earth’s axis is tilted at 23 degrees and 26 minutes toa line perpendicular to the Earth’s orbit around the Sun.

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Poles

The two points of this axis, which are 90 degrees above, or below the equator are the north and southpoles of the Earth.

Equator The imaginary line, which cuts the Earth’s globe into two equal parts and is perpendicular to the axis of the Earth, is known as the Equator Fig 1.5. It divides the Earth’s sphere into two equal halves called the

northern and southern hemispheres. All points at the equator are equidistant from the north & southpoles.

Geographical Longitudes and Latitudes

Longitude

Fig. 1.5

If we draw imaginary lines of concentric circles on the globe of the Earth (concentric means having thesame or common center as the center of the Earth), passing through the north and south poles, then

these circles will cut the Equator at right angles. These imaginary lines are known as the meridians of Longitudes (Fig. 1.5). Longitude is measured east or west of the Prime meridian. The Prime meridian onthe Earth passes through the original royal Greenwich Observatory near London. Therefore themeridian passing through Greenwich is considered the circle of zero longitude and all places falling onthis meridian have 0 degrees Longitude. It was accepted as the prime meridian of world at theWashington Conference of 1884. All places located east of this meridian have 0 to 180 degrees EastLongitudes and places located west of this meridian have 0 to 180 degrees West Longitudes. 180degrees east and 180 degrees west is the same meridian circle lying opposite to Prime meridian and iscalled the International Date Line.

Latitude

Fig. 1.6

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T h e M e r id i a n s o f L o n g i t u d e

T h e P a r a l l e l s o f L a t i t u d e

9 0 ° N

8 0 ° N

6 0 ° N

4 0 ° N

2 0 ° N

4 0 ° S

0 ° t o 9 0 ° N

N o r t h

S o u t h2 0 ° S

E q ua t o r



If we draw imaginary circles parallel to the Earth’s equator the centers of which fall at the axis of theEarth, these imaginary lines are known as parallel of Latitudes (Fig.1.6). All places located at theequator have 0 degree Latitude. Place located North of equator will have 0 to 90 degrees NorthLatitudes and places located south of equator will have 0 to 90 degrees South Latitudes dependingupon the location of these places. The point of intersection of 0 degree longitude and the Earth’sequator is the reference point for locating any place on the Earth.

Fig. 1.7

In short we can say that the longitude of a place is the angular distance of the place’s meridian, east or west of the prime meridian. Whereas latitude of a place is its angular distance north or south of the

equator, measured along its meridian. With these coordinates namely the longitude and latitudes, anyplace on the Earth can be located. The prime meridian of other heavenly bodies is defined with respectto a known surface feature.

The Moon

It is the only natural satellite of the Earth. We consider moon as luminary although it does not have lightof its own. It shines due to the reflection of Sun’s Light falling on it.The mean distance of Moon from Earth is 3,84,000 kilometers and its mean eccentricity is 0.0549.

Fig. 1.8

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L o n g i t u d e a n d L a t i t u d e

1 3 5 ° E1 8 0 °

8 0 °

6 0 °

2 0 ° N

4 0 °

2 0 ° S

0 °

4 0 °

1 0 5 ° E

7 5 ° E

1 3 5 ° W

4 5 ° E

8 0 °

7 5 ° W

1 0 5 ° W

4 5 ° W

1 5 ° W1 5 ° E

D i r e c t io n o f t h e E a r t h ’ s R e v o l u t io n

P a t h o f O r b i t

E a r t h ’

M o o n

S u n



Planetary Motion It was believed that planets had uniform circular motion round the Sun. Kepler explained the ellipticalorbits of planets around the Sun. Aphelion (1+e) is the point which is farthest from the Sun andPerihelion (1-e) is the point which is minimum from the Sun. For the Moon’s orbit round the earth weuse the word Aphelion as Apogee and Perihlion as Perigee. Aphelion : The distance of a Planet round the Sun = a (1+e)Perihilion : The distance of a Planet round the Sun = a (1-e)

At apogee the Moon is 406680 kilometers away from the Earth . At perigee the Moon is 35604 kilometers away from the Earth.

Note: - Here “a” is the mean distance between the Sun and a given Planet whereas “e” is theeccentricity of the orbit. No planetary orbits are circular in shape, but are elliptical having two diameters,one longest and the other shortest. With the result that they do not have one center or the focus but twocenters or foci.

Celestial SphereIf we imagine extending the surface of the Earth indefinitely on the heavens on all sides, with theobserver remaining at the center, we get what is known as the Celestial sphere, the cosmic sphere or Bramhand. As observer can observe only half of this celestial sphere as an inverted bowl over his head.

Similarly if we extend the Earth’s axis indefinitely on both the side to meet the celestial sphere, we getthe celestial north and celestial south poles (Fig.1.9).

Fig.1.9

Celestial Equator Similarly if we extend the Earth’s equator indefinitely on the heavens, we will get an imaginary greatcircle, which will cut the celestial sphere into two equal halves (Fig 1.10). This is known as the celestialequator. It divides the celestial sphere into northern celestial hemisphere and southern celestialhemisphere.

The entire celestial sphere together with all the planets appears to rise in the east and set in the west.This is due to the Earth’s own rotation on its axis from west to east.

The Position of a body on the celestial globe showing the spherical co-ordiantes of a star is shownbelow:

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T h e Z e n i t h

T h e S u n

N o r t h

T h e C e l e s t ia lN o r t h P o l e

S

E c l i p t i c

C e l e s t i a l E q u a t o r

K

&

&

Q

- ll

d

BC

P



Fig 1.10

Here, P = Polar Star (Dhruva)

ϒQΨ = Celestial equator

K = Pole of the ecliptic (Kadamba)

ϒ Ο = Plane of the ecliptic

Aries( ϒ) = First point of Aries (Vernal Equinox)

Cancer(Ο ) = First point of Cancer (Summer Solstice)

Libra (Ψ) = First point of Libra (Autumnal Equinox)

α = First point of Capricorn (Winter Solstice)

S = A heavently bodyPS = Great circle through P,S cutting equator at Q.

ϒQ = Right Ascension = α

QS = Declination = δ

KS = Great circle through K, S. cutting ecliptic at C.

ϒC = Celestial longitude = λ

CS = Clestial latitude = β

ϒB = Polar longitude or Dhruvaka = l

BS = Polar latitude or Vikshepa = d

The position of a stellar body may be defined by either its right ascension (α) and declination (δ) or its

celestial longitude (λ) and latitude (β).

Ecliptic An explained earlier, we follow the geocentric observations with the Earth at the center of the universeand all other heavenly bodies in revolution around it. Sun also likewise appears to revolve around theEarth, rising in the east and setting in the west. The apparent path of the Sun (which is actually the pathof Earth around the Sun) is known as ecliptic. This ecliptic is tilted at an angle of 23 degrees 26 minutesapproximately to the celestial equator due to the slant of the Earth’s axis (Fig.1.11). This angle betweenthe planes of ecliptic and equator is called the obliquity of the ecliptic and is 23 degree 26 minutes 25.2seconds at preset. Due to various influences of other planets this obliquity changes very slowly with

time.

Fig. 1.11

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Zodiac

The broad belt of about 16-degree extending 8-degree on either side of the ecliptic, in which all the

planets revolve, is known as Zodiac (Fig 1.12). This 16 degrees wide and 360 degree elliptical band inthe heavens is divided into 12 equal parts or imaginary compartments of 30 degree each. They arecalled the signs of zodiac. Each sign is named after a prominent constellation situated in it. There are 27Nakshatras or constellations of 13 degree 20 minutes each located in each sign.

Fig 1.12

Formation of Days & Nights

Due to the rotation of the Earth on its axis once a day, the zodiac also appears to revolve on its axisonce a day with all the Signs, Planets and Nakshatras located in it (Fig 1.13). This phenomenon alsogives rise to formation of Days & Nights on Earth.

Fig 1.13

The First point of Aries or the Vernal EquinoxWhen the Sun crosses from the southern celestial hemisphere to the Northern Hemisphere are reachesthe point of intersection of celestial equator ecliptic, it is known as the first point of Aries in sayanasystem of astrology. It is also called the vernal or spring equinox (Fig. 1.14). It occurs around 21st Marcheach year. Day & Night are of equal period or 12 hrs. each on this date.

The First point of Libra or the Autumnal EquinoxWhen the Sun crosses from the northern celestial hemisphere to the Southern Hemisphere and reachesthe point of intersection of celestial equator and ecliptic, it is known as the first point of Libra in sayanasystem (Fig 1.14). It is also called the autumnal equinox and occurs around 23 rd September each year.On this day too day & night are equal.

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T h e R o t a t i o n o f t h e E a r t h - D a y & N i g h t

A x

i s N o r t h P o l e

S u n

S o u t h P o l e

T h e e a r t h r o t a t e s f r o m w e s t t o e a s t o n i t s a x i s .

D a y

N i g h t

S I D E V I E W O FZ O D I A C

M A R SS A T U R N

S U N

M E R C U R Y

V E N U S

J U P I T E R

U R A N U S

N E P T U N E

E A R T H

C E N T R E O F E A R T H

C E N T R E O F S U N

8 °8 °

P L U T O



Fig. 1.14

Summer Solstice & Winter Solstice: When Sun starts its Northern Course that is on 13 th January everyyear it is called the Winter solstice. Sun enters Capricorn on this date and in Hindu Astrology it is calledMakar Sakranti or entry of Sun in Capricorn. Similarly entry of Sun in Cancer is called the Summer Solstice.

Declination: Declination of a Planet is its angular distance North or South of the celestial equator depending upon the Planets position and measured along the meridian through th Planet.Sidereal Period : Sidereal period is the true time of complete revolution of a planet around the Sunwith reference to distant stars.Sidereal Year :The sidereal year is the mean period of revolution of revolution of Earth in its orbit withrespect to a fixed star due to precession of the equinoxes(explained in the chapter) The length of thesidereal year is 365.256 in mean solar days.Tropical year : Tropical year is the time of the passage of the Sun from one vernal equinox to the nextvernal equinox. The vernal equinoctial point recedes by 50.2388475 sec therefore the Sun has to travel

this much distance less than 360 degrees to arrive at the new vernal equinoctial point therefore thetropical year is less than the sidereal year by the time taken by the Sun to traverse 50.2388475 sec .which is about 20 min. 26 sec.

Rahu and Ketu ( Dragon Head & Dragon Tail)

Rahu and Ketu have been considered in Hindu astrology as equivalent to planets. They are not physicalbodies but only mathematically calculated sensitive points having immense influence over the nativitieson Earth.

Moon in its orbit, on a northerly course from south to north, crosses the ecliptic. This point of intersectionis known as Rahu or Dragon’s head. 180 degrees away from this point, Moon on its southerly course,from north to south, again crosses the ecliptic. This point is known as Ketu or Dragon’s tail. Moon’s orbitis also inclined to the ecliptic (Fig 1.15) and hence on each such intersection the Sun, Earth and Moon

are not in a straight line and eclipse does not occur.

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Fig. 1.15

As Rahu and Ketu are only sensitive points having no physical entity of their own, they are calledshadowy planets or chhaya grahas. At Rahu and Ketu Moon’s latitude is zero, as Moon is on eclipticitself. Rahu and Ketu are not stationary in space but have a mean motion of about 19 degree and 30

minutes per year, and take about 18 years and 6 months to make a revolution around the Earth. Thismotion of Rahu & Ketu is retrograde most of the time.

Inclination of Earth’s axis and its significance

The Earth’s rotational axis is tilted at an angle of 23 degrees 26 minutes and 25.2 seconds to thevertical to ecliptic. During the Earth’s sojourn in its orbit, the Sun appears to move northwards or southwards relative to the Earth giving rise to seasons.

Summer solstice occurs around 21st June when Northern Hemisphere gets direct sunrays causingsummer season. The Sun at this point is at its north most position having latitude of 23 degree and 26minutes north. The line joining all points at this latitude is called the Tropic of Cancer .

Similarly, around 22nd December, at winter solstice southern hemisphere gets direct sun rays causing

winters in the northern hemisphere. The Sun at this point is at its south most position having latitude of 23 degree 26 minutes south. The line joining all points at this latitude is called the Tropic of Capricorn.

Around 21st March and 23rd September the Sun appears overhead at the equator causing vernal andautumnal equinox respectively. Vernal equinox is also known as the first point of sayana Aries and is thereference point for much astronomical and astrological calculation. At winter solstice the Sun turnsuttarayana in sayana system which means that it turns northwards.

In Hindu astrology however after applying ayanamsha correction (explained later), the Sun becomesuttarayna around 14th January each year in the present era. This coincides with Makar Sankranti or thesolar ingress into the Capricorn sign. Similarly around 21 st Jun Sun turns dakshinayana in sayanasystem which means that it turns southwards in its sojourn.

Sayana, Nirayana

The vernal equinox or the first point of Aries is the point of intersection of celestial equator with eclipticwhere the Sun crosses from south to north. This first point of Aries in the sayana system Sa + ayanameans with ayanamsha. In the present era the first point of Aries in sayana occurs around 21 st Marcheach year. This point is not fixed and the equinox is moving westwards each year with reference to afixed star. At the time of the Sun’s passage from vernal equinox, the Earth is 50.2388475 seconds of thearc westwards with reference to (Polar Star) fixed star, than the Earth was at the same equinox in theimmediately previous year. The regression of equinox is known as the precession of equinoxes.

In Nirayana system however the first point of Aries is fixed with reference to a background star. Thisfixed star is Spica in the Chitra nakshatra and 180 degree from this star is the nirayana first point of Aries. The difference between this fixed initial point and the Vernal equinox is known as Ayanamsha,which separates the sayana and nirayana systems. The fixed first point of Aries in nirayana (fixed withreference to a background star) is always at an angle of 180 degree to the chitra star. The word

Nirayana is derived from Nir + ayana which means without ayanamsha.

Planetary longitudes are measured from the vernal equinox, which gives us the sayana position. After applying ayanamsha correction to this, we get the nirayana longitudes. Western astrologers follow thesayana position of planets whereas Hindu astrologers follow the nirayana system.

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Precession of Equinoxes

Fig. 1.16

Precession of equinoxes referred to above can be explained as a wobbly motion of a rapidly spinningbody (Fig.1.16). The Earth is not spherical and is bulged at the equator. The attraction of the Moon andthe Sun exerts a gravitational torque, which slowly changes the direction of its rotational axis. Thisproduces a circular movement of the celestial pole near the North Pole of the ecliptic, resulting in a slowregression of the intersection of celestial equator with the ecliptic. The coordinates of any planettherefore alter with time in the moveable zodiac.

The precession of equinoxes is at the rate of 50.2388475 seconds per year.

AyanamsaAyanamsa is the rate at which the point of intersection of the Ecliptic & the celestial equator moves in

retrograde motion. The correct Ayanamsa is given by the figure 50.2388475". You should know that theNirayana zodiac & the Sayana zodiac were in the same degree in the year 291A.D.For casting the horoscope help can be taken from the K.P. Ephemeris or by Lahiri Ephemeris. Astrologers can take the help of correct software too available in the market. It is worth noting that K.P.& Lahiri Ephemeris are taking the same Ayanamsa but Lahiri had taken 285 A.D. as the year of coinciding of both the zodiacs. Astrologers should add 6’ to Ascendant. & all the positions of the planetsin case they are using Lahiri Ayanamsa.

Sidereal Day and Solar Day

Fig. 1.17

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The apparent solar day is from one sunrise to the next sunrise. In other words it is the differencebetween the two successive sunrise times from any location. The mean solar day therefore would bethe average length of the day in a year.

The time taken for the Earth to rotate once on its axis with reference to a fixed star is called the siderealdays. The sidereal month and year can also be defined similarly. The length of sidereal day is about 23hours and 56 minutes and is about 4 minutes shorter than the mean solar day. This difference is caused

by the Earth’s orbital motion in the following manner:

Look at Figure 1.17, at A, a point on the Earth faces the Sun. After making 90 rotations on reaching B,the Earth must move one fourth rotation more to enable the same point on the Earth to face the Sun. Onreaching C, after 180 rotations, it must make half rotation more to face the sun and so on till it reachesback at A after making 360 rotations or one revolution around the Sun. At this point it must make onemore rotation for the same point to face the Sun. In fact at the end of each rotation on its axis, the Earthmust rotate a little more to complete one apparent solar day.

Now let us understand the situation if the Earth was moving with reference to a fixed star. On movingfrom A to B, after 90 rotations, it need not move the additional one fourth rotation to face the fixed star.Similarly after 360 rotations, the Earth need not move one more rotation. Thus we understand that thesolar day is longer than the sidereal day.

In 360 sidereal days = 1 additional solar day24 hours

In one sidereal day = 24 x 60 / 3604 minutes more.

A sidereal day therefore is shorter than the mean solar day by about 4 minutes. Since we know that amean solar day is of 24 hours, the sidereal day is of 23 hours and 56 minutes. As there are 365.25 daysin a year and not 360, hence the duration of a sidereal day is 23h 56m 4.091s.

The Earth is rotation on its axis once in a day but for an observer, the celestial sphere is rotating. Thussidereal time is the local time reckoned according to the apparent rotation of the celestial sphere. Inother words whenever time is reckoned with reference to sidereal day, it is called sidereal time. Thesidereal time is zero when the first point of Aries in sayana or the vernal equinox crosses the observersmeridian. Sidereal time can therefore be defined geometrically as the hour angle of vernal equinox.

Fig. 1.18

Eclipses An eclipse is the total or partial disappearance of a celestial object behind another. When a celestialbody comes within the shadow cast by another body or when another obscures the light from onecelestial body, an eclipse occurs. The Sun is our illuminating body around which all the other planets arerevolving. In this interplay of journeys of planets in their orbits when the three heavenly bodies fall in thesame line the eclipses occur. Since an eclipse is the temporary obscuring of luster or brilliance of one’spower, the eclipse always occurs when the particular heavenly body is its best in brilliance and power.

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C o u n t e r c l o c k w i s e a t t h e N o r t h P o l e .

N . P .

N . P .

W

D i re c t i o n o f R o t a t i o nE a s t w a r d a t t h e E q u a t o r

E q u a t o r

E



The Solar EclipseThe Sun gets eclipsed on a New Moon day when it is at its best in brilliance. It occurs when the Sun ispartially or fully hidden by the Moon. For this eclipse to occur the Moon must come in between the Earthand the Sun and for an observer on the Earth, the Sun gets obscured and will not be visible. Thefollowing conditions must be fulfilled for the solar eclipse to occur.

1. It must be a New Moon or amavasya.

2. The Moon must be near Rahu or Ketu.3. The latitude of Moon should be near zero.

A solar eclipse can occur only on a new moon day when the Moon is weakest (not visible) and Sun at itsbest in strength and brilliance and this gets eclipsed. Further the longitudes of Moon and Rahu or Ketumust be very near. The latitude of Moon should be near zero and this will happen only when Moon is onor near the ecliptic.

It is a matter of chance that the angular diameter of the discs of Sun and Moon are equal. Therefore theMoon cannot hide the Sun for more than few minutes. However when Moon is at apogee, its angular size is slightly smaller than that of the Sun.

Solar eclipse is of three types.

Total Solar Eclipse: When Moon is at perigee (nearest to the Earth) the disc of the Moon is slightlylarger than that of the Sun, and for the observer the Moon will completely cover the Sun’s disc causing atotal solar eclipse Fig. (1.19). It happens when the angular size of the Moon exceeds that of the Sun (asat perigee) and the line joining their centers intersect the Earth’s surface. As the Earth and Moon aremoving in their orbits the point of intersection moves very rapidly across the Earth’s surface and sweepsout a narrow band called path of totality or annualarity. (Depending on whether it is a total solar eclipseor annular solar eclipse). It is never wider than 300 kilometers but can be thousands of kilometers long.The area of total shadow is called umbra. The speed of Moon’s shadow ranges between 1800 km/hr to8000 km/h depending upon its position. Therefore a total solar eclipse can not last for more than sevenand half minutes for any location.

Fig. 1.19

Partial Solar Eclipse :When only part of Sun’s disc is covered by the Moon, only a partial solar eclipse occurs. This isobserved beyond the path of totality explained above. The area of partial shadow is called penumbra.

Annular Solar Eclipse :

When Moon is farthest from the Earth (as at apogee) and the angular size of the Moon is slightly smaller than that of the Sun then during the eclipse the observer sees a dark lunar disc surrounded by a brilliantring of Sun’s eclipse is observed only during day time from the lighted surface of the Earth.

Fig. 1.20

14

T o t a l s o l a r E c l i p s e

A n n u l a r S o l a r E c l i p s e



The Lunar EclipseMoon gets eclipsed on a full Moon day when it is at its best caused by Sun’s reflected rays. When theEarth comes in between the line of Sun and Moon and the Earth’s shadow falls on the lunar surface alunar eclipse occurs( Fig 1.21). The totality of Earth’s shadow on the Moon is called umbra and thepartial shadow is called penumbra. At the Moon’s distance the angular radius of Earth’s umbral shadowis two and a half times the Moon’s angular diameter. Therefore the period of total lunar eclipse may be

maximum of 1 hour 40 minutes. The lunar eclipse too can be total or partial depending up the position of observer on the Earth. The lunar eclipse is observed only during night from the dark surface of the Earthon full moon night. Here also the longitude of Moon and Rahu or Ketu should be near and the Moon’slatitude should be zero.

Fig. 1.21

Due to the inclination of Moon’s orbital plane to the ecliptic, eclipses do not occur on every new Moonand the full Moon days. If the Moon’s orbit had coincided with the ecliptic then on every Full Moon andNew Moon there would have been a lunar or solar eclipse respectively. Moon in its orbit crosses theecliptic twice. At these moments the conditions for eclipses to occur get fulfilled. The time of occurrence,duration and circumstances of solar and lunar eclipses depend up the changing geometry of Earth –Moon – Sun system. This geometry repeats exactly after 18 years and 10 years therefore any eclipse isexactly repeated after this period. This is called Saras.

Phases of the Moon

Fig. 1.22

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T o t a l L u n a r E c l i p s e

P h a s e s o f t h e M o o n

G i b b o u s

F i r s t Q u a r t e r

C r e s c e n t

S u n ’ s

R a y ’ sD a yN i g h t

S u n ’ sR a y ’ s N e w M o o n

T h i r d Q u a r t e r

R e

v o l u t i o n

G i b b o u s

M

o

o

n

’ s

F u l l M o o n



Sun in lesser time than Jupiter. In the second position the Jupiter appears to be in Gemini to theobserver on Earth. This is why the Superior planets appear to move in retrograde motion when they arein opposition to Sun.

Retrogression of Inferior Planets (Mercury & Venus)Inferior Planets retrograde when they are in between Sun & Earth. They move fastest in a forward

motion when Sun is in between them & Earth. In the figure 1.24, see the initial position of Earth,E1 &

Fig. 1.24

Mercury M1. E2 & M2 are the positions of Earth & Mercury after some time. Motion of Mercury is morethan the motion of Earth. In figure it is clear that an observer on Earth will observe Mercury in the Sign,Virgo in the initial position & will observe it in Leo in the second position. This is how the phenomenon of retrogression takes place in case of inferior planets i.e. Mercury & Venus. Note that these planets alsocombust while in retrograde motion.

Rising, Setting and Combustion of Planets

Sun is so bright that any planet that comes near to its longitude becomes invisible as seen from theEarth because the brilliance of Sun totally overshadows the existence of such a planet. Thisphenomenon when the planet becomes invisible to the naked eye, as viewed from the Earth, due toconjunction with Sun is called helical setting of a planet. When the planet becomes visible, thereof it isknown as rising of a planet.

Combustion of a Superior Planet

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R E T R O G R E S S I O N O FI N F E R I O R P L A N E T S

J 2

J 1S U N

E 2

E 1S U N



Fig. 1.25

Whenever superior planet comes near the Sun it moves faster. It is explained in the figureabove. E1 & J1 is the initial position of Earth & Jupiter respectively in Fig1.25. E2 & J2 are theposition after some time because both are moving in same direction Native on earth willobserve that the planet is moving at more speed.

Combustion of inferior Planets

Inferior planets combust when they are in between Sun & Earth (Position1) and also whenthey are on the other side of the sun (Position 2)

Fig. 1.26Kya kar diy figure ka

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E 2

S U N

A q ua r i u

s

J 2

J 1 E 1

S a

g i t t

ari u

s

C a p r i c o r n

R E T R O G R E S S I O N O FI N F E R I O R P L A N E T S

J 2

J 1S U N

E 2

E 1S U N



When inferior planets are between Sun & earth they appear to moves in backward direction,retrograde motion.

Position 2

Fig. 1.27

M1 & E1 are the initial positions of Mercury & Earth. M2 & E2 are the positions of Mercuryand Earth after some time. Since both Earth & Mercury are on not on the same side of theSun and are moving in same direction. Mercury will appear to move at faster speed fromEarth.

Conclusion:

Inferior planets appear to move at faster speed when they are on the other side of Sun &appear to move backwards when they are in between Earth & Sun.This phenomenon of setting of a planet is also called the planet becoming combust. The longitudinaldistance between the planet and Sun which makes a planet combust are:

Planet Distance from Sun Planet Distance from Sun

Moon 12 Degree Jupiter 11 DegreeMars 17 Degree Venus 9 DegreeMercury 13 Degree Saturn 15 Degree

There are, however, divergent viewpoints with regard to the above mentioned degrees in direct or retrograde motion of planets.

Planetary warsWhen two planets are positioned in identical degree i.e. within 1 degree of each other, they are said tobe at war.

Note: Retrogression, Combustion & Planetry wars are Astronomical phenomenon & have nosignificance in Natal Predictive Astrology.

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E 2

S U NA q u a r iu s M 1

M 2

E 1

P u s i c s

C a p r i c o r n



TIMEModern Time MeasuresThe length of an astronomical year is 365.25 days or 365 days, 5 hours, 48 minutes, 45.2 seconds. Acommon year has 365 days and it becomes necessary once in four years to add a day to the year making it a leap having 366 days. The modern division of time is as follows:

60 seconds = 1 minute60 minutes = 1 hour 24 hours = 1 day7 days = 1 week30 days (commonly) = 1 calendar month365 days or 12 months = 1 year 366 days = 1 leap year 100 years = 1 century

Zodiac measure will be used later, for calculation of horoscope, hence they may be understood here : -

60 seconds ( “ ) = 1 minute ( ‘ )60 minutes ( ‘ ) = 1 degree ( º )30 degrees ( º ) = 1 sign or rashi

12 Signs or 360 degrees = zodiac

Longitude and Time

1 second or longitude ( “ ) = 1/15 second of time1 minute of longitude ( ‘ ) = 4 seconds of time1 degree of longitude ( º ) = 4 minutes of time15 degrees of longitude = 1 hour 360 degrees of longitude = 24 hours

Greenwich Mean Time or Universal Time A mean solar day is equal to 24 hours irrespective of the various factors explained above. The mean

solar time on the prime meridian of Green is chosen to be the Greenwich Mean Time (GMT) or theUniversal time. Noon at 12.00 Hours GMT occurs when the mean Sun crosses the Greenwich meridian. Almost all countries of the World follow the time which is + or – of GMT.

Local Mean TimeThe duration of a mean solar day is 24 hours. Whenever the Sun crosses the meridian circle of aparticular place, it is local noon for that place. At this moment the hour angle of the Sun is zero. Whenthe hour angle is 12, it is mid-night for that place having Local Mean Time (LMT) as zero, and the newday commences. Thus LMT is the time elapsed from the midnight of the place. Let us understand itmore elaborately.

The Earth rotates on its axis once in a day in 24 hours or 24 x 60 = 1440 minutes. This rotation is of 360degrees. Therefore to rotate 1 degree the Earth will take 1440/360 = 4 minutes. Due to this rotation onits axis, the Sun appears to rise in the east and set in the west. The eastern parts of the Earth getsunrise earlier and each 1 degree longitude towards the west gradually get the sunrise later, at about 4minutes interval. This time difference of 4 minutes per 1degree longitude is not uniform due to variousfactors like latitude, tilt of Earth’s axis etc. The time of each place therefore will be different and is calledthe Local Mean Time of the particular place.

Standard TimeThe local mean time of all places having different longitudes will be different even within a state, zone or country. If all the places, cities or towns were to follow their own LMT, things would become everydifficult and a chaotic situation may arise. What will then be the time followed by the Airlines, Railways,Television etc? To solve this problem a uniform time is chosen either by a law or general usage, whichacts as a standard time for the country.

The Earth is divided into 24 Time Zones. These run from North to South, a bit like lines of Longitude.

When it is 12 Noon in Greenwich, it is 1o’ clock in the afternoon at places in the first time zone to theEast, 2 o’clock at places in the second time zone & so on.

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Moscow in Russia, is in the third time zone to the East. That means when it is 12 Noon in England, it is3o’clock in the afternoon in Moscow.New Zealand is twelve time zones ahead. This means that it would be midnight in New Zealand when itis Noon in England.New York is five time zones behind. This means that when it is Noon in England it is 7 o’clock in themorning in New York.

In India, before 1880 each city followed its own LMT. From 1-1-1880 LMT Madras became popular which was 5h 20m 50s ahead of GMT. From 1-1-1906 +5:30 Hrs. time zone was adopted for all over India and termed and Indian Standard Time or IST. It relates to 82degree 30’ E meridian or time zone of +5:30 Hrs. ahead of GMT.

Even though all watches show IST in India, the sunrise and sunset will vary according to longitude of theplace. The sunrise in the eastern longitudes, say in Calcutta will be much earlier than the Jaipur as per IST. But in Hindu astrology it is the concept of LMT, which is more important for all calculations.

Zonal Standard Time (ZST) and Time ZoneIn bigger countries like the United States of America, the longitudes vary so much across the countrythat even a single standard time will not serve the purpose. So for the purpose of time, the country isdivided into various zones. The standard time for each zone is called the Zonal Standard Time or ZST.

In USA there are four official standard of times, the Eastern, Central, Mountain and Pacificcorresponding to the local mean times of 75, 90, 105 and 120 degrees west meridians. Canada has thesame divisions with one additional time zone called the Atlantic time corresponding to 60 degrees westmeridian.

The standard meridian of any country or any zone in a big country is also called the time zone and isexpressed in terms of + or – difference from GMT depending on its longitude towards east or west. Asalready explained the meridian passing through Greenwich has 0 degrees longitude. The LMT of this 0degree longitude is called GMT and is the standard reference point for all place on the Earth.

DAYS

1. Apparent Solar Day : Is from one midnight to the next i.e. from 00:00 hours to 24:00 hours. Itis longer than the sidereal day by about 4 minutes.

2. Savana Day : In Hindu system the apparent solar day is the period of one sunrise to the nextand is called a savana day.

3. Mean Solar Day: The average of all the days in a year is called mean solar day. Its duration is24 hours in mean solar time.

4. Sidereal Day : A complete rotation of the Earth on its axis with reference to a fixed star isknown as sidereal days. Its duration is 23 hours, 56 minutes, 4.091 seconds in mean solar time. It is also called a mean sidereal day.

MONTHS

1. Solar Month : A solar month is determined on the Sun’s entry into a sign or rashi. In theHindu system there are different rules of determining the beginning of a solar month

i.e. the sunrise rule, the sunset rule and the midnight rule ect. In the western astrology it iscalculated on the solar ingress into a sign in sayana system. Whereas in Hindu astrology it iscalculated on the solar ingress into a rashi in nirayana and is called sankranti.

2. Lunar Month: A lunar month has two pakshas called the shukla paksha and the krishnapaksha each having 15 tithies. In shukla paksha (the bright half) tithies are from 1 to 15. The15th tithi is called purnima or the Full Moon. In the krishna paksha (the dark half) tithies areagain from 1 to 15. The 15th tithi here is called amavasya or the New Moon. Two types of lunar months are follows :

A] The New Moon ending lunar month covering the period from one New Moon to thenext. It is called Shukladi or Amanta (derived from amavasya + anta). It is followed inGujarat, Maharashtra and Andhra Pradesh etc.

B] The Full Moon ending lunar month covering the period from one Full Moon to the

next. It is called Krishnadi or Purnimanta (derived from purnima + anta). It is followedin Madhya Pradesh, Uttar Pradesh, Bihar, Punjab, Delhi and Rajasthan etc.

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AYANASThere are two ayanas. The first ayana is uttarayana when the Sun starts its northerly course at winter solstice from the Tropic of Capricorn. The second ayana dakshinayana when the Sun starts itssoutherly course at summer solstice from the Tropic of Cancer.

The period when the Sun is transiting the signs of Capricorn to Gemini is known as the period of

uttarayana Sun. the period in which the Sun is transiting the signs of Cancer to Sagittarius is known asdakshinayana Sun. The Hindu seasons called ritus are also related to the ayanas. The ritus of shishir (winter), basant (spring) and grishma (summer) occur during uttarayana. The remaining three ritus of varsha (rains), sharad (autumn) and hemant (winter) occuring during dakshinayana. As per Hinduastrology Uttarayana is considered auspicious by Hindus.

Day:

5. Nakashatra Day : In Hindu system a sidereal day is called a Nakshatra day and is the timetaken from one rising of a nakshatra to its next rising.

6. Lunar Day : It is also called a tithi. It is an important concept in Hindu astrology. When Moongains 12 degrees over that of the Sun’s longitude, one tithi is completed. There are 30 tithies ina lunar month, 1 to 15 in each of the shukla and krishna pakshas. The mean duration of a tithiis 23 hours, 37 minutes, 28.096 seconds. The tithi is determined at sunrise. Whenever between one sunrise and the next, three tithies occur, there is akshay tithi or the cancellation of the titihi. Let us take an example. Sunrise is at 5:30 AM and pratipada or the 1 st tithi is running.Immediately thereafter say at 5:45 AM next day before the next sunrise. Hence at the nextsunrise the third tithi will be running. In this case the 2 nd tithi gets cancelled and is called akshay tithi. Similarly if one tithi continues for two successive sunrise times, it is called an extratithi or adhik tithi.

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