Posts Tagged ‘eclipse’

Kodaikanal Observatory as a potential world astronomy heritage site

Posted in Blogs (Articles) on September 29th, 2012 by Rajesh Kochhar – Be the first to comment

Colloquium given at Indian  Institute of Astrophysics Bangalore, 25 September 2012

Rajesh Kochhar

President IAU Commission 41: History of Astronomy

Indian Institute of Science Education and Research Mohali

[email protected]

As is well known, Unesco has a mission to safeguard and preserve world heritage sites. Towards this end, it prepares a World Heritage List, in which cultural properties from all over are inscribed (that is included) . Additionally, Unesco encourages international cooperation in heritage conservation. Unesco has now undertaken a Thematic Initiative on ‘Astronomy and World Heritage’. It has enlisted technical assistance from International Astronomical Union for this purpose. Within IAU, the responsibility has been entrusted to Commission 41: History of Astronomy. Phase I of this Initiative aims at ‘acquiring an in-depth knowledge of the outstanding properties connected with astronomy in all geographical regions through their identification, study and inclusion of the most representative of these properties on the national tentative lists. Phase II aims at promoting the most outstanding of these properties which recognize and celebrate achievements in science through their inscription on the World Heritage List.

In simpler words, an astronomical property must first enter its nation’s tentative list and then campaign for inscription in the World List. Note that Unesco does not deal with individuals, only with member countries.


You are all familiar with the rust-free iron pillar near Qutub Minar at Mehrauli in Delhi. It is famous the world over for its metallurgy. What is not so well known is its astronomical significance. It was brought to Delhi in relatively recent times, that is 1233 CE. It was originally installed in  about 400CE in Udaigiri, Central India, on Tropic of Cancer, as a gnomon. If this pillar had remained at its original location, it would have been an obvious choice as a world astronomical heritage property.


As things stand, I think the only candidate for astronomical world heritage list from India would be the Solar Physics Observatory Kodaikanal ( est 1899 ), which now has solar picture data with the same instrument for the longest period in the world (since 1912), except for some short interruptions due to maintenance/ upgradation.


Since you are all practitioners of science ( and not merely historians), I will try to place Kodaikanal in the larger context of development of  solar physics as a scientific discipline.

By the middle of the 19th century, physical astronomy, as distinct from positional astronomy, had already taken some shape, thanks to the advent of  solar spectroscopy and photography. There were a number of solar eclipses in quick succession and visible from India : 1868, 1871 and 1872. These eclipses brought observers from Europe into India, and gave a fillip to solar instrumentation and studies the world over. In 1868, the French astrophysicist Pierre Jules Cesar Janssen discovered helium from Guntur . During his post-eclipse stay at Simla, Janssen created the first spectro-helioscope, which facilitated daily examination of the sun.

Then came the 1874 Transit of Venus. The scientists’ agenda for it ran deep. What was advertised was the brief passage of Venus in front of the solar disc; what was planned was a long-term study of the disc itself.

British (and European) solar physicists wanted photograph of the sun for each day of the year. Since this was impossible in Europe’s weather conditions, data was needed from the colonies.

The British Association for the Advancement of Science passed a resolution asking the Government of India to make arrangements for observing the event and to provide instruments which were afterwards to be transferred to a solar observatory. Such was the prestige enjoyed by science and scientists in Europe at the time that the British Empire, as the owner of the most of the world’s sunshine, agreed to help, though partially.


The 1874 transit eventually led to regular solar physics studies in India, even though the exercise took 25 years. The initiative came from the influential British  scientist of the time , Sir Norman Lockyer.To sum up in advance, the step-wise developments were as follows. First, express arrangements were made for the observation of the 1874 event from Roorkee. Next, interim facilities were created at Dehra Dun and Poona for collection of data and its transmission to Europe. Finally, a permanent solar physics research facility was set up at Kodaikanal.


The 1874 event

 It is noteworthy that Survey of India ( and not Madras Observatory) was asked to make transit  observations. More than 100 photos of the sun were taken at Roorkee  and sent to the Astronomer Royal Sir George Biddell  Airy. Photos from all over were reduced by Captain G. L. Tupman who wrote: ‘There is only one really sharp image in the whole collection, including the Indian and Australian contingents, and that is one of Captain Waterhouse’s wet plates taken at Roorkee’.


Dehra Dun Observatory (1878-1925)

 Lockyer used his equation with Lord Salisbury, the Secretary of State for India, for making arrangement for solar photography in India. Salisbury wrote to the Viceroy on 28 September 1877: ‘Having considered the suggestions made by Mr. Lockyer, and viewing that a study of the conditions of the sun’s disc in relation to terrestrial phenomenon has become an important part of physical investigation, I have thought it desirable to assent to the employment for a limited period of a person qualified to obtain photographs of the sun’s disc by the aid of the instrument now in India’.  From the technical details given in the letter , it is clear that it was drafted by Lockyer himself. Accordingly, starting from early 1878,  solar photographs were regularly taken at Dehra Dun  under the auspices of Survey of India, and sent to England every week. Dehra Dun continued solar photography till 1925, but more out of a sense of duty than enthusiasm.


The larger of the two photoheliographs fell into disuse, and in 1898, Lockyer was stung by on-the-spot discovery that ‘the dome has been taken possession of by bees’.The arrangement was discontinued in 1925, and equipment sent to Kodaikanal.


St Xavier’s College Observatory, Calcutta (1879)

 Sunny India caught the attention of astronomers in the continent also. The Italian transit-of-Venus team led by Professor P. Tacchini of Palermo Observatory stationed itself in Bengal, its Chief instrument being the spectroscope, `an instrument not recognized in the equipment of any of the English parties’. A co-opted member of the Italian team was the Belgian Jesuit Father Eugene Lafont (1837-1908), the popular professor of science at the elitist   St. Xavier’s College. Lafont was  no researcher himself was an inspiring educator and science communicator.

Tacchini suggested to Lafont ‘the advisability of erecting a Solar Observatory in Calcutta, in order to supplement the Observations made in Europe, by filling up the gaps caused in the series of solar records by bad weather’. Lafont used his influence with Europeans, Anglo-Indians  (half-castes), rajas, zamindars, and Indian men of note, and soon collected  a substantial sum of Rs 21000 through donations, including Rs 7000 from the Lieutenant Governor of Bengal.

A  9 in refractor by Steinhill of Munich was purchased and housed in a spacious dome constructed for the purpose.

No research or teaching use was ever made of  this facility. This is unfortunate. If the experiment had succeeded, observational astronomy might have become part  of Indian education system. As it is, astronomy has largely remained decoupled from  college/ university teaching.



Takhtasinghji’s Observatory Poona  (1888-1912)

      It was a Government Observatory, named after the principal funder, Maharaja of a princely state, Bhavnagar. It was India’s first modern astrophysical observatory. Unfortunately, it was created for an individual and did not last long. The original plan was to establish a spectroscopic laboratory at Elphinstone College Bombay for use by the students. The initiator of the proposal was a lecturer in the College, Kavasji Dadabhai Naegamvala (1857-1938), who obtained seed money of Rs 5000 from the Maharaja of Bhavnagar and a matching grant from the Bombay Government.  While in England in 1884 for buying the equipment,  he was persuaded by the Astronomer Royal and Lockyer to build a spectroscopic observatory instead.


Since Poona was a better astronomical site than Bombay, in 1885 Naegamvala was transferred  there to College of Science where the Observatory came up in 1888. Its chief instrument was a 16½ inch aperture silver-on-parabolic glass Newtonian  made by Grubb. In addition, Lockyer equipped Poona as a satellite facility. A six-inch Cooke equatorial purchased by the Government for the 1874 transit observation from India had been  loaned to Lockyer’s Observatory in South Kensington.


The India Office also purchased two spectroscopes from Hilger (one solar, the other stellar) for his use. The equatorial and the spectroscopes were given to Naegamvala so that he could observe with them and send raw data to Lockyer. Similarly, data was received  by Lockyer and more generally in England from Kodaikanal and Mauritius.


Not surprisingly, relationship between Poona and South Kensington was non-symmetrical. Whenever South Kensington found fault with data collection at Poona, it did not write directly to Naegamvala, but formally complained to his British superiors. Yet, when Kodaikanal Observatory was being planned, Lockyer suggested Naegamvala’s name for the directorship. The position was however offered to an Englishman, Charles Michie Smith, a non-descript physics professor at Madras. Lockyer and Astronomer Royal constituted two independent centres of power in England, and Kodaikanal came under the latter’s sphere of influence.


Naegamvala took observations till the very last date of his employment, 11 January 1912. The Observatory was officially abolished on the day of his retirement and  all equipment was sent to Kodaikanal. Thus instead of creating a permanent educational facility, a temporary research centre was created for the primary benefit of European solar physicists.


Kodaikanal Observatory (1899)

       If the 1874 transit of Venus was important for solar physicists, so was the severe famine of 1876-77 in the Madras Presidency. Monsoons fail at times, but the severity of famines was particularly high in the colonial period because of large-scale export of food grains from India to Britain  in utter disregard of local requirements. Astronomers of course would not worry about avoiding famines, but in predicting monsoon behaviour. In 1879, Lockyer presented a report to the Indian Famine Commission claiming that famines were correlated with sunspot minima.

There is no doubt that Lockyer and many others genuinely believed in a correlation with solar activity and terrestrial weather. But  it is also a fact that the practical benefits to be derived from a study of the sun were exaggerated to gain Government support. In 1881, Government of India’s chief meteorologist Henry Francis Blanford reported to the Famine Commission that no such simple sunspot-monsoon correlation as suggested by Lockyer existed.


In any case, the Government decided to go ahead with the Solar Observatory. It was however decided to wait till the neurotic Madras Astronomer Pogson was dead. This happened in 1890.

Kodaikanal started shakily. The first task was the acquisition of instruments; they came from a variety of sources.

A photoheliograph (Dallmeyer No. 4) originally made for the 1874 transit was given on loan by Greenwich to Kodaikanal. It was used till 1912. Madras had acquired a 6 in telescope on English mounting, by Lerebours and Secretan of Paris, in 1850. It was remodelled in 1898 by Grubb of Dublin who provided it with an electric drive, and mounted a 5 in aperture a 5 in aperture  Grubb photographic lens on the frame. These and other pictures have now been digitized.


The most important event in the Kodaikanl Observatory’s history was the arrival of George Evershed in 1907, who chose to come to India  no doubt to be able to work in solitary splendour. Kodaikanal rose to great heights under him. His first task was the installation of Ca-K spectroheliograph that had been received in 1904, from Cambridge Scientific Instruments Company. His 1909 discovery of the radial flow in sun spots_ the Evershed Effect_ is the only major discovery ever made from Kodaikanal.In 1911, he made an auxiliary specroheliograph and bolted it to the existing instrument. The Sun could now be photographed not only in Ca-K light but also in H-alpha.


This is the only time a state-of-art pure astronomical instrument was ever made in India.

These old twin spectroheliographs are no longer in use. The H-alpha pictures were discontinued in about 2005, and  the Ca-K  in about 2007. In the mean time, in 1995, as a back-up, Ca-K line filtergrams using a CCD camera were begun.      Finally, in 2008 a newly constructed  twin telescope was commissioned to take pictures in Ca-K and white light. In other words, Kodaikanal does not take H-alpha pictures any more. It takes Ca-K pictures all right, but with a new equipment, as in the Spectro building and white-light pictures at two places ( North Dome and Spectro).In 1933, a Hale spectrohelioscope was received as a gift from Mount Wilson Observatory.


The Spectroheliograph building, known locally as Spectro, has a priceless clock from the 18th century. It is among the dozen odd gridiron pendulum clocks made by John Shelton for the 1761 or 1769 ( probably the latter) transit of Venus. It is not known when and how one of the Sheltons ended in India. The clock was one of the original instruments at Madras Observatory (est 1787). It was transferred to Kodaikanal in 1899. It is still working, and is in use as an ordinary clock.


International Geophysical Year 1957-1958 provided an opportunity for ordering three new instruments. Two of these, Lyot heliograph, and Lyot coronograph, were never really utilized. The third instrument, acquired on turn-key basis, was the Solar Tunnel Telescope which was commissioned by M. K. Vainu Bappu, who joined as Director in 1961. This was the last time Kodaikanal got a new instrument.Over the years many minor instruments were obtained; and new temporary  ctivities initiated ( radio, magnetic/ionospheric). At present, the Tunnel Telescope, Spectro, and the North Dome are the only regular activity centres of  Kodaikanal Observatory.

Kodaikanal was never a well-endowed Observatory. Told instruments cwere often canabalized o meet current requirements, for example an eclipse expedition.There was therefore lot of improvisation; cutting up of old instruments to make new ones for solar eclipse expeditions, e. g.

About 25 years ago, I traced the history of almost every instrument, or parts thereof, that was in actual existence or was mentioned  in the Store’s Stock Register. Many of these details have been published ( eg in Vistas in Astronomy). Here I have drawn attention to only some of them.

  • Indian Institute of Astrophysics Bangalore ( whose field station Kodaikanal Observatory is) has a priceless instrumentation heritage. It deserves to be documented case by case  and preserved.
  •  Kodaikanal Observatory has always been an important feature on the  town’s tourist map. The Observatory however needs to revamp its Outreach Programme, and ,make it more attractive and interactive.
  • Many buildings in the Kodaikanal campus are lying unused. Utilizing them for a combination of heritage, curriculum-based education and science popularization will help preserve the buildings also. The Kodaikanal Observatory needs to be protected not only as cultural property but as real estate also.


Concluding remarks

Kodaikanal Observatory is a respected name in the world solar physics. Many better-known observatories have discontinued their old programmes, or even shifted to new locations, and become more high tech.

IIA should prepare a detailed dossier on the Observatory. Persuade  India’s Ministry of Human Resource Development ( Indian node for Unesco) to include it in the national list.

Then work towards getting it inscribed in the Unesco World Heritage List.






























Rahu and Ketu in mythological and “astronomological” contexts

Posted in Blogs (Articles) on August 13th, 2010 by Rajesh Kochhar – 2 Comments

Indian Journal of History of Science, Vol, 45, no.2, June 2010, pp. 287-297

Rajesh Kochhar


Rahu and Katu were deployed as planetary deities in the sixth century CE immediately after the mathematical theory of eclipses was propounded by Aryabhata. Their literary credentials however go back to early Vedic times. Here our aim is to examine, in a joint mythological and astronomical-astrological (“astronomological”) context, how the textual meanings of Rahu and Ketu have evolved with time. There are clear stages in their evolutionary histories, which must be borne in mind while interpreting early references.

The legend of Rahu shows signs of internal development. Successor to the Rgvedic Svarbhanu, Rahu as eclipse-causing demon was reduced to a body-less head so that the swallowed sun or moon had an escape route. Rahu’s identification with the lunar ascending node represents an attempt to connect new scientific developments with traditional beliefs. Ketu, in contrast, was a dictionary word used to denote a variety of related phenomenon especially comets. The promotion of the head-less body as a demon represents expansion of mythology in the light of new scientific developments. Ketu was now given an additional entirely new role, creating avoidable confusion. Significantly, Ketu’s iconography represents efforts at reconciling its two disparate roles.

Key words: mathematical theory of eclipses, astrology, Vedic mythology, planetary deities, Buddhist mythology, astronomical omens, ritual

Ancient Indian perception of the moving cosmic environment two millennia ago was bipolar. Orbits of the seven geocentric planets (graha) by virtue of their predictability represented cosmic order, while phenomena like meteors, comets and eclipses which did not fit into any pattern were classified as utpata, portent or calamity. This world view is preserved in a Buddhist Sanskrit text, Sardulakarnavadana, the legend contained in which is known to have been translated in an abridged form into Chinese in 265 CE (Vaidya 199,p.xi) . As the 5th century CE came to a close, the status of eclipses was modified.

Mathematical theory of eclipses was propounded in India in 499CE by Aryabhata (born 476 CE) in his influential Siddhantic treatise simply known as Aryabhatiyam (See Ohashi 2009 for a recent review). According to this theory, solar and lunar eclipses occur when the moon is at either of its orbital nodes. These theoretical points move in a direction opposite to that of the planets and complete an orbit in the rather short period of 18.6 years. This development was immediately taken note of in astrological literature, which classified the two nodes as planets, implying that they were now amenable to mathematics. Since they were hypothetical they were dubbed shadow planets. The 6th century CE text Brihajjataka (2.2-3) by Varahamihira (died 587 CE) includes Rahu and Ketu in the list of planets, and even gives their synonyms: Tamas, Agu and Asura for Rahu; and Shikhi for Ketu (Rao 1986, p.76), which however never gained currency. The two nodes are 180 degrees apart so that specifying one fixes the other. It would thus have sufficed to include just one of them. Both were listed no doubt to bring the planetary number up to nine which was considered sacred.

If new words had been coined to designate the two nodes, matter would have rested there. But both Rahu and Ketu are terms of Vedic vintage. The term Rahu had previously been used as a proper noun and exclusively in connection with eclipse so that its deployment represents an attempt at integrating new scientific developments with ancient tradition. On the other hand Ketu was merely a common noun employed variously but never in association with eclipse. Here then was an old term which was given an entirely new identity, representing expansion of mythology in the light of new scientific developments.

It is not uncommon to see even earlier references to Rahu and Ketu being interpreted in terms of their later status. This is unfortunate, because it distorts the history of the evolution of “astronomological” thought. The new coinage is advisedly used in preference to the extant terms astronomical and astrological to avoid backdating the present differentiation into earlier times when they would have been essentially seen as one. Our aim is to investigate how the textual meanings of the terms Rahu and Ketu have evolved with time. We must keep in mind some notable features of the available source material. Most texts remained open for a long time and were contributed to by generations of authors. There is no reason to expect or demand internal self- consistency from them. The texts were often composed in metrical poetry and were meant for a select audience. Very often the meaning assigned to a particular word depends on the context in which it is used.

An important source of information on ancient India is the Mahabharata which was expanded over a long period of time to include matter that went beyond the description of the Bharata battle which it had originally set out to describe. The astronomical content of the Mahabharata is consistent with Vedic astronomy in that it marks sky positions with the help of bright stars or star groups known as naksatra. The Mahabharata is not familiar with the twelve zodiacal signs which make their appearance in post-Mauryan India in about the first century BCE at Baudha Gaya where they are depicted on the railing pillars (Kane 1975, p. 598). Given the size and the nature of the contents of the Mahabharata it is reasonable to assume that if zodiacal signs had been introduced into India when the Mahabharata text was still open they would have found their way into it. We thus conclude that the Mahabharata text had been closed by about 1st century BCE (Kochhar 2000, p.56). This is an important datum. At one place the Mahabharata (Vanaparva 188. 87-88) does say that “when the moon, the sun and Jupiter in Tisya come together in one rasi, krta age will begin”. The term rasi is used here in the general sense of a portion of sky, not in the precise sense of a zodiacal sign.

The Mahabharata does not make any reference to the week days either. There is no unanimity on the epoch when they were introduced into India. Varahamihira, already referred to, in his other works , Pancasiddhantika and Brihatsamhita, mentions week days while quoting authorities who had lived much earlier . From this it has been inferred that week days were introduced into India in the first century CE(Kane 1975, pp. 680-1). A more plausible case has been built by Markel (1991) to suggest that the week made its appearance in India only in forth century CE.

Vedic Rahu and Ketu

The Rgveda does not know of Rahu. Rgveda (5.40:5-9) describes how Svarbhanu, son of an asura, pierced the sun “through and through with darkness”. The eclipse caused great distress among observers: “All creatures looked like one who is bewildered, who knoweth not the place where he is standing”. The sun himself appealed to Atri: “Let not the oppressor with this dread, through anger, swallow me up, for I am thine, O Atri”. In response, “By his fourth sacred prayer Atri discovered Surya concealed in gloom that stayed his function”. “The Brahmana Atri, as he set the press-stones, serving the Gods with praise and adoration, established in the heavens the eye of Surya, and caused Svarbhanu’s magic arts to vanish. The Atris found the Sun again, him whom Svarbhanu of the brood of Asuras had pierced with gloom. This none besides had the power to do.” (Griffith 1896, p. 255) .The Atris were prominent contributors to the Rgveda. The whole of the fifth mandala is authored by them. The passage quoted above is mentioned and embellished at a number of places in the Vedic literature :Tandya Brahmana (4.5.2; 4.6.13; 6.6.8; 14.11. 14-15; 23.16.2), Gopatha Brahmana (8.19), Satapatha Brahmana (, and Sankhayana Brahmana (24.3) ( Dikshit 1896, Vol.1, p.58; Kane 1975, pp. 241-242). What the Atris probably did was to chant mantras while the eclipse lasted. The Rgvedic description is significant. An eclipse was seen as the demon’s work in disrupting the cosmic order. Propitiation was needed to restore that order.

Dikshit (1896, Vol. 1, p. 57) while translating a passage from the Rgveda renders Svarbhanu as Rahu and goes on to give its meaning as the lunar ascending node. Similarly Kane (1975, p.569), while discussing a reference in the Maitrayani Upanisad, equates Rahu and Ketu with the ascending and descending node respectively. Svarbhanu’s career as an asura did not last long. It is not clear when and how Svarbhanu made way for Rahu, who appears for the first time, and as the sun’s enemy, in Atharvaveda (19, 9-10). Chandogya Upanisad (8.13) makes an interesting analogy: The “soul that has acquired true knowledge is said to shake off the body after casting off all evil” like “the moon becoming free from the mouth of Rahu” (Kane 1975, p.569).The Pali Buddhist sources refer to the moon and the sun freeing themselves from the clutches of Rahu by invoking Buddha’s name (Candima Sutta, Samyutta-nikaya 2.9; Suriya Sutta, Samyutta-nikaya 2.10).

Mahabharata (Bhismaparva 13.39-45) uses both Svarbhanu and Rahu as interchangeable names. Rahu is a graha, 12000 yojanas in diameter, bigger than both the moon (11000 yojanas) and the sun (10000 yojanas). Rahu had to be bigger than the sun and the moon so that it could grab them. Note that the term graha here carries the sense of a grabber and not that of a body in orbit. In course of time, the name Svarbhanu came to be de-stigmatized so much so that a son of Lord Krsna was given the name (Mani 1975, p. 778).

Atharvaveda (13.16-24) employs Ketu to mean ray of light. These nine verses are taken from Rgveda (1.50.1-9) in the same order and more or less in the same form. They are also found “in one or more other Vedic texts” (Whitney 1905, Vol.2, p.722). More typically Ketu meant combination of fire and smoke. The Atharvaveda passage (19.9.10) quoted above refers to Dhumaketu as an epithet of mrtyu [death]. It either means a comet or literally as “smoke-bannered” to the smoke rising from a funeral pyre (Whitney 1905,Vol. 2, p. 914). Atharvaveda (11.10.1-2, 7) uses Ketu in the plural, as arunah ketavah [ruddy Ketus]. Here the reference seems to be to comets or meteors. Varahamihira’s Brihatsamhita, composed in 6th century CE but containing much older material, quotes a still earlier astronomer Garga on a class of 77 comets, called Aruna, which are dark red in colour (Bhat 1981,Vol. 1, p.138).

Puranic Rahu and Ketu

If the demon Rahu devours the sun or the moon to cause an eclipse, how do they become visible again? The answer is provided by the well – known story samudramanthana (churning of ocean), described in Mahabharata, Visnupurana and elsewhere. In the story, the demon Rahu’s head is chopped off, which survives. It is the Rahu head which causes an eclipse. Since the rest of the body is missing, there is an escape route for the sun and the moon. Note that the name Rahu now belonged to the body-less head. The head-less body would remain unclaimed, till the 6th century CE; see below. Brhatsammhita (5:1-3) while narrating this story also refers to a prevalent alternative belief that Rahu is of a serpentine form with only the head and the tail. The ancient Iranian text Bundahishn talks of goshir, an eclipse-causing serpent. It is not clear whether Varahamihira is referring to the Iranian legend or an un-recorded Indian one. Al Biruni writing in the 11th century reserves the name Rahu for the dragon’s head and calls the tail Ketu (Sachau 1888, Vol. 2, p.234).There were some half-hearted attempts to relate eclipses to predictable phenomena. Thus it was speculated that an eclipse took place when five planets get together (Brihatsamhita 5.17)

Mahabharata (Adiparva 65. 11-12, 31) names Kasyapa as the father and Simhika as the mother of Rahu, who is at times designated Simihkeya after her. His three other real brothers are also mentioned, their given names, Sucandra, Candraharta and Candrapramardana, all being associated with moon. Kasyapa from another wife Danu had 34 named sons including one called Ketuman (not Ketu).Curiously the names Surya, Candramas and Svarbhanu figure in the list (Adiparva 65.22-26).These 34 demons are thus Rahu’s half brothers. This naming is an exrecise in meaningless creativity. This association may have an astronomical basis which does not seem to have been noted before. Varahamihira in his Brihatsamhita (3.7; 11.22) mentions a class of 33 comets known as Tamaskilakas (dark shafts), called children of Rahu. They were noticed by the 11th century astronomer and chronicler Al-Biruni also. Described as black, and shaped like a crow or a beheaded man or a sword, or bow and arrow, they are always in the neighbourhood of the sun and the moon. It is likely that this category include sunspots (Bhat 1981, pp.25-26). An ancient authority quoted by Varahamihira on Tamaskilaka is Garga, who figures in Mahabharata also as an astronomer and advisor ( Mani 1975, p. 280). He may well have been responsible for constructing a myth about 34 half-brothers of Rahu out of the description of Tamaskilakas. It is noteworthy that from independent considerations Garga has been place at about 100 BCE (Kane 1975, p.681), the epoch we have assigned to the closure of the Mahabharata.

Inverted astronomy in Mahabharata

The Mahabharata talks about the prevalent astronomical knowledge albeit often in an inverted manner. It will be useful to inspect the context in which these references were made.

When the two rival armies stood confronting each other, and the Bharata war looked imminent, last ditch efforts were made to avert it by appealing to the ineffectual king Dhrtarastra whose villainous sons were widely held responsible for bringing things to such a pass. To convey the enormity of the sense of impending genocide, the king was told that in anticipation of the war the natural order had already broken down. The effect was heightened by the fact that the so-called eye witness account was brought to the sightless king by his own biological father. The revered Ved Vyasa tells Dhrtarastra (Bhismaparva 3.46) as follows.

Cows are giving birth to asses; and elephants to dogs. Sons are enjoying sexual pleasures with their mothers. Idols of gods are laughing, vomiting blood, feeling sad, and falling off their pedestals on their own. Animals are being born with three horns, four eyes, five feet, two urinary organs, and two tails. Women are giving simultaneous birth to four –five girls, who immediately start singing, dancing and laughing. Trees are flowering out of season. Lotus and water-lily are blossoming on tree tops. Even koel, peacock and parrot are making fearsome sounds. There is a downpour of blood and bones from the sky.”

The imagined weirdness of the world in anticipation of the fratricidal war was extended to the skies as well. “Arundhati well known for her devotion to her husband Vasistha has left him behind. [The reference here seems to be the star pair in Ursa Major rather than to individuals.] Dawn and the dusk look like as if they are on fire. Vyasa tells Dhrtarastra that he could not make out the difference between day and night, because the sun, moon and the stars all were burning bright throughout. This is a fearsome sign. Although it was the Kartika full moon night, the moon was not visible; its luster had given way to fire.

It is in this background that even the more-reasonable sounding descriptions of celestial phenomenon should be seen. A recurring theme is the reference at various places in the Mahabharata to Rahu, as if the occurrence of an eclipse was at par with holocaust on earth. “Rahu has seized the sun” (Bhismaparva 3.11). “Rahu is approaching the sun” (Bhismaparva 141.10).”Rahu swallowed the sun most untimely” (Salyaparva 55.10). “Rahu eclipsed the sun and the moon simultaneously” (Asvamedhaparva 76. 15, 16, 18). Meteors (ulka) and earthquakes are also similarly invoked. As part of the celestial foreboding it is stated that a very dangerous Dhumaketu has overcome the naksatra Pusya. This will bring destruction to both sides. (This ill-omen appears in the 4th century CE Buddhist text Sardulakarnavadana as well; see below).

Continuing, his listing of ill omens, Ved Vyasa tells Dhrtarastra that the sveta graha (white planet) has transgressed Citra, while the parusa graha (harsh planet) has established itself between Citra and Svati (Bhismaparva 3.11, 16). The translators have exercised their own discretion in rendering these terms. Sveta graha has been left untranslated (Sathe et al. 1985, p.39) or equated with Ketu (Ganguli 1884-1896, Book 6, p.12). Parusa graha has been identified with Rahu by one translator ( Ganguli 1884-1896, Book 6, p.12) and with Ketu by ANOTHER (Sathe et al. 1985, p.39).. The arbitrariness is obvious. As we have argued it would be anachronistic to associate Rahu and Ketu with a planet in pre-Varahamihira times.

Greek astronomical elements made their documented appearance in India in 149 CE when a Greek astro-text was translated into Sanskrit by Yavanesvara. It was versified in 269CE by Sphujidhvaja under the title Yavanajataka (Pingree, p. 1959). The versification was a significant development, because it signifies assimilation of Greco-Babylonian elements into Indian tradition. And yet, Vedic astronomical tradition remained extant even after the introduction of Yavana texts, as can be seen from passages in Sardulakarnavadana, already referred to. “Irrespective of the naksatra, when the sun or the moon is seized by Rahu, the king along with his subjects comes to pain.” “Irrespective of the naksatra when Ketu enters the moon, the neighbouring enemy king gets the upper hand.” “When Dhumaketu establishes itself in the Pusya naksatra, then defeat in enemy’s assault from all four directions is guaranteed” (Vaidya 1999, p. 374, couplets 462,463, 466). As we have already noted, Dhumaketu in Pusya as a bad omen is mentioned in the Mahabharata also. It is significant that Ketu and Dhumaketu are listed separately and along with Rahu under utpata.

Once the mathematical theory of eclipse was propounded, Rahu ceased to be an utpata; its predictability however did not remove the fear associated with it. On the other hand, Ketu as comet continued to be an utpata. Brihatsamhita assigns separate chapters to a discussion on eclipses under the heading Rahu and on comets under Ketu. Brihatsamhita does not mention Ketu in the context of eclipse. As mentioned earlier, it is Varahamihira’s other text Brihajjataka which twins Ketu with Rahu as the eclipse-causing shadow planets, introducing the concept of navagraha. Ketu was now given a brand new identity; the torso which had been lying lifeless after the detachment of the Rahu head was now resurrected and named Ketu.

We have argued that inclusion of the demon Rahu in the list of mathematically tractable planets took place after 499CE. Support for this conclusion comes from iconographic data. The “ first surviving depiction of Rahu occurs in a relief of the ‘Churning of the Ocean’ carved over the façade of the doorway of cave-temple number nineteen at Udayagiri in the Vidisha district of Madhya Pradesh, which can be dated to ca. A.D.430-450. Earliest known representations of Rahu as a member of the planetary deities are those on two stone lintels, 100cm by 20cm, originally from the villages of Nachna and Kuthara in the Panna district in the Bundelkhand region of Madhya Pradesh, most likely sculpted during the reign of the Uccakalpa king Jayanatha (r. ca. A.D.490-510)” ( Markel 1990, pp.11-13). If the assigned dates are correct, it is remarkable that Rahu’s planetization occurred within a decade of Aryabhata’s theory. Ketu as a planetary deity appears in about 600 CE or a little later, in Uttar Pradesh. In the eastern state of Orissa, Ketu was not counted in until the tenth century, which thus had only eight grahas till then (Markel 1990, p.21). One wonders whether it was from Orissa that Rahu as Yahu travelled to Burma as one of the eight nats (spirits).

Astronomical literature employs the term Rahu in connection with eclipse but in a number of ways. Aryabhata does not use either Rahu or Ketu; he and following him many others refer to a node as pata. Brahmagupta (b.598CE) in his long career displays signs of intellectual evolution. Taking a position contrary to Aryabhata, he in his Brahmasphutasiddhanta, prepared in 628 CE, expresses his faith in the demon Rahu as the cause of eclipse . Al Biruni noted this (Sachau 1888,Vol. 2, p.110). His later text, Khandakhadyaka (665 CE), however, calculates eclipses in a matter-of-fact way employing the technical term pata and without naming Rahu or Ketu (Chatterjee 1970, pp. 80-85).

The 689 CE astronomical handbook Karanaratna by Devacarya (Shukla 1979) uses Rahu to denote the eclipse shadow (2.2) as well as the ascending node (e.g.1.15). Significantly, at one place (1.13) the latter is called Rahumukha (Rahu head). A tersely written basic astronomical text will have no reason to mention Ketu. As comet, meteor or the like Ketu lay outside the scope of theory while as descending node it would be redundant once the ascending node Rahu or pata was mentioned.

In later Iranian (and Arabic) mythology the ascending node Rahu and the descending node Ketu become the head and the tail of the dragon Al –Djawzahr. Ketu as comet is not forgotten; he figures as al-Kayd (Hartner 1965). Rahu and Ketu as part of mathematical astronomy were introduced into China during the Tang dynasty (618-907CE), but with modified meaning. While Rahu was retained in the sense of the lunar ascending node, Ketu was used as a designation for lunar apogee (Niu 1995)

The imagery and iconography of Rahu and Ketu have evolved over time, with the latter having been more difficult to conceptualize. While Rahu has been well-defined since the days of the samudramanthana story, Ketu had in the sixth century CE the eclipse role thrust upon him in addition to the cometary ( and not the other way round as Neugebauer (1957, p.211) suggests).

The tradition of eclipse calculation has continued uninterrupted till relatively recent times. A copper plate inscription tells us about the grant of a village by the Kalachuri king Ratnadeva II to an astronomer , Jagannatha by name, for correctly predicting the lunar eclipse of 1128CE. He knew two Siddhantas and succeeded where other astronomers in the court failed. Hence the reward ( Mirashi 1933-34,p.161).Seven centuries later, a Pondicherry-based traditional astronomer calculated for the benefit of John Warren the lunar eclipse of 1825 May 31-June 1, with the help of shells, placed on the ground, and from tables memorized “by means of certain artificial words and syllables”. The results were remarkably accurate for the time. There was an error of +4 minutes for the beginning, -23 minutes for the middle and -52 minutes for the end (Neugebauer 1983, p.436). Traditional almanacs still use old algorithms for their planetary position calculations, but have taken to using modern methods for calculating eclipses as a concession to the greater time consciousness of the present times.

To sum up, the terms Rahu and Ketu have been continuously in use since the early Vedic times, but their meaning has not remained static. Rahu was an eclipse-causing demon whose name was confined to the severed head in the samudramanthana story. In the sixth century CE, Rahu was identified with the ascending node of lunar orbit and designated the eighth planet.

From the earliest time till the sixth century CE, Ketu was not a proper noun but a dictionary word used to denote phenomena like comets and meteors. This meaning continued later as well. But in the sixth century CE, Ketu was made into a proper noun by identifying it with the descending node of the lunar orbit and designating it the ninth planet. The headless body of the demon left behind from the samudramanthana days was retrospectively named Ketu. This evolutionary sequence needs to be kept in mind while interpreting textual references. More specifically, identification of Rahu or Ketu with a planet in a text prior to Varahamihira would be an exercise in anachronism.

I thank Yukio Ohashi, K.T.S. Sarao, B.V. Subbarayappa, K. Ramaubramaniam and Michio Yano for help and useful conversations.


(To help place an author’s work in context, date of original publication is cited in the text. For convenience, date of translation or reprint, mostly facsimile, is added.)

Bhat, M. Ramakrishna (1981) Varahamihira’s Brihat Samhita (Delhi: Motilal Banarasidass).

Chatterjee, Bina (1970) The Khandakhadyaka of Brahmagupta with the commentary of Bhattotpla, Vol. I. ( Delhi: Motilal Banarasidass).

Dikshit, Sankar Balakrishna (1896) History of Indian Astronomy (English translation by R.V. Vaidya, Pt I,1968; Pt II, 1981. New Delhi: India Meteorological Department).

Ganguli, Kisari Mohan (1884-1896) Mahabharata of Krishna-Dvaipayana Vyasa ( on-line)

Griffith, Ralph T. H. (1896 ) The Hymns of the Rgveda ( Reprint, Delhi : Motilal Banarasidass, 1973).

Hartner, W. (1965) “ Al-Djawzahar”. In :Encyclopedia of Islam,Vol.2 ( Leiden: Brill), pp.501-502.

Kane, Pandurang Vaman. (1975) History of Dharmasastra, Vol. 5 (Poona: Bhandarkar Oriental Research Institute).

Kochhar, Rajesh (2000) The Vedic People (Hyderabad: Orient Longman).

Mani, Vettam (1975) Puranic Encyclopaedia (Delhi: Motilal Banarasidass).

Ohashi, Yukio (2009) “The mathematical and observational astronomy in traditional India”. In: Science in India, Vol. 13, Pt.8 (ed. J.V. Narlikar) (New Delhi: Viva Books), pp 1-88.

Markel, Stephen (1991) “The genesis of the Indian planetary deities”. East and West, Vol. 41. pp. 173-188)

Markel, Stephen (1990): The Imagery and Iconographic Development of the Indian Planetary Deities Rahu and Ketu”. South Asian Studies, 6:9-26.

Mirashi, V.V. (1933-34) Epigraphia India, Vol. XXII, 159-165.

Neugebauer, Otto (1957) “Notes on Al-Kaid”. J. Amer. Oriental Soc., 77, 211-215.

Neugebauer, Otto (1983) Astronomy and History : Selected Essays ( New York : Springer-Verlag).

Rao , Bangalore Suryanarain (1986) Varahamihira’s Brihat Jataka ( Delhi : Motilal Banarasidass, Reprint 2008).

Sachau, Edward C. (1888) AlBeruni’s India, ( 2 vols reprinted as one , Delhi : Atlantic Publishers)

Sathe, Shriram: Deshmukh, Vijaya; and Joshi Prabhakar ( 1983) Bhartiya Yuddha: Astronomical References ( Pune : Shri Babasaheb Apte Smarak Samiti).

Shukla, Kripa Shankar (1979) Karana-Ratna of Devacarya ( Lucknow : Lucknow University).

Vaidya, P. K. (ed.) (1999) Divyavadana ( Darbhanga: Mithila Institute).

Whitney, William Dwight (1905) Atharva-veda-samhita, 2 vols. (Cambridge, USA: Harvard University).

Yano, Michio (2003)”Calendars, astronomy and astrology” .Blackwell Companion to Hinduism (ed.:Cavin Flood)( Oxford: Blackwell)

Aryabhata reinstalled

Posted in Blogs (Articles) on August 16th, 2009 by Rajesh Kochhar – 2 Comments

Rajesh Kochhar

Aryabhata (born AD 476) is the founder of Siddhantic astronomy which focused on developing mathematical algorithms for calculating planetary orbits and for predicting lunar and solar eclipses. His concise text, composed in AD 499 and known simply as Aryabhatiyam ( Aryabhata’s), influenced all subsequent work on the subject. From Aryabhata’s time till that of Kepler’s laws, Siddhantic astronomers were probably the only ones in the world who could calculate eclipses with any degree of accuracy.

Very little is known about Aryabhata himself. This is so because of the inherent limitations of the oral tradition. Astronomical texts were composed in terse metrical poetry, which was memorized and transmitted from one generation to the next by word of mouth. What was not considered worth preserving for the moment was lost for ever. It is thus not possible to construct a connected account of ancient astronomy or for that matter of any aspect of ancient India.

Internet has given birth to a flourishing industry of concocting details about Aryabhata and others and giving such details wide currency. By attributing to Aryabhata what he did not do , we would be belittling what he actually did.

Here is some authentic information on Aryabhata arranged in question- and- answer form.

Q1. What do we know about Aryabhata, the person?

A. First note that his name is spelt with a single t and not two. He was born in AD 476 and composed his work Aryabhatiyam in AD 499. This we learn from the book itself. The year of his death is not known.

Aryabhata says that he “ sets forth here the knowledge honoured at Kusumpura”. This has been interpreted to mean that Kusumpura was his work place. It has been identified with Patliputra which in turn has been equated with modern Patna.

This is all what we know about Aryabhata from him. Some additional information comes from his commentators ( e.g. the earliest, Bhaskara I ( AD 629)), who declared that Aryabhata hailed from a place , or district, called As’maka. It has not been possible to identify Asmaka. Legend prevails that Aryabhata hailed from Kerala. There is no basis for this. It is a well known fact that Aryabhata’s work was followed and improved upon in Kerala. Attempts to place Asmaka in Kerala may simply be manifestation of a desire to give physical basis to this intellectual relationship.

Bhaskara I also calls Aryabhata Kulapa. By a long shot this has been interpreted to mean that he was the vice-chancellor of Nalanda University! Kulapa could simply mean founder of a school, which Aryabhata certainly was.

The press coverage of 22 July 2009 total solar eclipse claimed that Aryabhata maintained an observatory at Taregna near Patna. This is an instance of history driven by tourism.

Inter-University Centre for Astronomy and Astrophysics, Pune, has erected a statue of Aryabhata to keep company with Galileo, Newton and Einstein. Bare-chested, stocky Aryabhata wearing a sacred thread is of course a figment of imagination. We have no way whatever of knowing what Aryabhata looked like.

Q2. Did Aryabhata believe in the spin of the earth?

A. He certainly did. But the whole thing should not be blown out of proportion.

We do not sense the spin of the earth under our feet. Instead the whole celestial sphere seems to be going around the earth. This indeed was the prevalent world view. Aryabhata boldly asserted that the earth was not static but spun on its axis.

He was severely criticized for this by friends and foes alike. His own follower Varahamihira died AD 587) believed that the earth was static. The otherwise brilliant mathematician astronomer Brahmagupta ( ) severely castigated Aryabhata for believing in the spin of the earth. Such was the onslaught of mainstream criticism that even followers of Aryabhata’s own school retreated. They rather ineffectually changed a word in the Aryabhatiyam text to argue that Aryabhata indeed considered the earth to be static.

If the scientific tradition had been based on written-down prose rather than on oral metrical poetry, Aryabhata’s reasons why he believed the earth spun would have been on record, and might have been considered convincing by later generations.

While today we give credit to Aryabhata for this, we should keep in mind that we know of Aryabhata’s belief in the spin of the earth not from his work or that of his followers but from the charge sheet maintained against him by his opponents. ( Just as we know about many nationalist heroes from the criminal complaint against them recorded by the colonial government.)

It is noteworthy that only a handful of later Indian astronomers believed that the earth rotated on its axis : Prthudaka (AD 860) and Makkibhatta ( AD 1377). Significantly , a religious text , Skandapurana ( , following Aryabhata, describes the earth as a bhramarika ( spinning top).

It should be borne in mind that belief in spin of the earth or otherwise was not relevant for Siddhantic calculations. Brahmagupta did not believe in in it . But that does not mean that he was any the lesser astronomer. Aryabhata himself , like everybody else, maintained that the sun revolved around the earth. As far as kinematics is concerned it matters not who goes around whom.

Aryabhata believed that the earth was all water south of equator ( Gola 12) and that it expanded in size by one yojana during a day of Brahma and contracted during a night( Gola 8).

As Thoreau put it , “ A man is wise with the wisdom of his age only and ignorant with its ignorance”.

Q3. Did Aryabhata believe in heliocentrism?

A. As discussed above , no , he did not. WE take heliocentrism for granted. In its time, it had profound philosophical implications that went beyond planetary theory.Impact of heliocentrism on human thinking should not be under-estimated.

Q4. Did Aryabhata invent zero?

A. No, zero had been known long before that.

Q5.Is Aryabhata the founder of the eclipse theory?

A. No. He is probably the first one to apply it in India. Such theories were already known in Greece and China FaceBook maxweb Twitter maxweb linkedin maxweb googleplus maxweb facebook facebook ChandigarhCity.Info facebook facebook