Indian astronomy

Some of the earliest forms of astronomy can be dated to the Indus Valley Civilisation or earlier. As in other traditions, there is a close association of astronomy and religion during the early history of the science, astronomical observation being necessitated by spatial and temporal requirements of correct performance of religious ritual. Thus, the Shulba Sutras, texts dedicated to altar construction, discusses advanced mathematics and basic astronomy. it includes the details about the Sun, Moon, nakshatras, lunisolar calendar. The Vedanga Jyotisha describes rules for tracking the motions of the Sun and the Moon for the purposes of ritual. According to the Vedanga Jyotisha, in a yuga or "era", there are 5 solar years, 67 lunar sidereal cycles, 1,830 days, 1,835 sidereal days and 62 synodic months. Greek astronomical ideas began to enter India in the 4th century BCE following the conquests of Alexander the Great. Other topics included definitions of different units of time, eccentric models of planetary motion, epicyclic models of planetary motion, and planetary longitude corrections for various terrestrial locations. ==Calendars==

The divisions of the year were on the basis of religious rites and seasons (Ṛtú). The duration from mid March–mid May was taken to be spring (vasanta), mid May–mid July: summer (grishma), mid July–mid September: rains (varsha), mid September–mid November: autumn (sharada), mid November–mid January: winter (hemanta), mid January–mid March: the dews (shishira). Hindu calendars have several eras: • The Hindu calendar, counting from the start of the Kali Yuga, has its epoch on 18 February 3102 BCE Julian (23 January 3102 BCE Gregorian). • The Vikram Samvat calendar, introduced about the 12th century, counts from 56 to 57 BCE. • The "Saka Era", used in some Hindu calendars and in the Indian national calendar, has its epoch near the vernal equinox of year 78. • The Saptarishi calendar traditionally has its epoch at 3076 BCE. J. A. B. van Buitenen (2008) reports on the calendars in India: ==Astronomers==

• Lagadha (1st millennium BCE): The earliest astronomical textnamed Vedanga Jyotisha| details several astronomical attributes generally applied for timing social and religious events. Since the texts written by 1200 BCE were largely religious compositions the '' has connections with Indian astrology and details several important aspects of the time and seasons, including lunar months, solar months, and their adjustment by a lunar leap month of Adhimāsa. Ṛtús are also described as yugāṃśas (or parts of the yuga, i.e. conjunction cycle). Aryabhata also mentioned that reflected sunlight is the cause behind the shining of the Moon. In Khandakhadyaka'' (A Piece Eatable, 665 CE) Brahmagupta reinforced Aryabhata's idea of another day beginning at midnight. • Varāhamihira (505 CE): Varāhamihira was an astronomer and mathematician who studied and Indian astronomy as well as the many principles of Greek, Egyptian, and Roman astronomical sciences. • Bhāskara I (629 CE): Authored the astronomical works Mahābhāskariya (Great Book of Bhāskara), Laghubhaskariya (Small Book of Bhaskara), and the Aryabhatiyabhashya (629 CE)a commentary on the Āryabhatīya written by Aryabhata. Bhāskara I's works were followed by Vateśvara (880 CE), who in his eight chapter Vateśvarasiddhānta devised methods for determining the parallax in longitude directly, the motion of the equinoxes and the solstices, and the quadrant of the Sun at any given time. • Lalla (8th century CE): Author of the Śiṣyadhīvṛddhida (Treatise Which Expands the Intellect of Students), which corrects several assumptions of Āryabhaṭa. The second parttitled Golādhyāya (chapter XIV–XXII)deals with graphical representation of planetary motion, astronomical instruments, spherics, and emphasizes on corrections and rejection of flawed principles. • Bhāskara II (1114 CE): Authored Siddhānta Shiromani| (Head Jewel of Accuracy) and '''' (Calculation of Astronomical Wonders) and reported on his observations of planetary positions, conjunctions, eclipses, cosmography, geography, mathematics, and astronomical equipment used in his research at the observatory in Ujjain, which he headed • Śrīpati (1045 CE): Śrīpati was an astronomer and mathematician who followed the Brahmagupta school and authored the Siddhāntaśekhara (The Crest of Established Doctrines) in 20 chapters, thereby introducing several new concepts, including Moon's second inequality. • Mahendra Sūri (14th century CE): Mahendra Sūri authored the Yantra-rāja (The King of Instruments, written in 1370 CE)a Sanskrit work on the astrolabe, itself introduced in India during the reign of the 14th century Tughlaq dynasty ruler Firuz Shah Tughlaq (1351–1388 CE). • Makarandacarya (1438–1478 CE): Author of the Makaranda sāriṇī • Parameshvara Nambudiri (1380–1460 CE): Creator of the Drgganita or Drig system, Parameshvara belonged to the Kerala school of astronomy and mathematics. Parameshvara was a proponent of observational astronomy in medieval India and he himself had made a series of eclipse observations to verify the accuracy of the computational methods then in use. Based on his eclipse observations, Parameshvara proposed several corrections to the astronomical parameters which had been in use since the times of Aryabhata. • Nilakantha Somayaji (1444–1544 CE): In 1500, Nilakantha Somayaji of the Kerala school of astronomy and mathematics, in his Tantrasangraha, revised Aryabhata's model for the planets Mercury and Venus. His equation of the centre for these planets remained the most accurate until the time of Johannes Kepler in the 17th century. Nilakantha Somayaji, in his Āryabhaṭīyabhāṣya, a commentary on Āryabhaṭa's Āryabhaṭīya, developed his own computational system for a partially heliocentric planetary model, in which Mercury, Venus, Mars, Jupiter and Saturn orbit the Sun, which in turn orbits the Earth, similar to the Tychonic system later proposed by Tycho Brahe in the late 16th century. Nilakantha's system, however, was mathematically more efficient than the Tychonic system, due to correctly taking into account the equation of the centre and latitudinal motion of Mercury and Venus. Most astronomers of the Kerala school of astronomy and mathematics who followed him accepted his planetary model. He also authored a treatise titled Jyotirmīmāṁsā stressing the necessity and importance of astronomical observations to obtain correct parameters for computations. • Daśabala ( 1055–1058 CE): Author of Cintāmanṇisāraṇikā (1055) and the Karaṇakamalamārtaṇḍa (1058). • Acyuta Piṣāraṭi (1550–1621 CE): Sphuṭanirṇaya (Determination of True Planets) details an elliptical correction to existing notions. Another work, Karanottama deals with eclipses, complementary relationship between the Sun and the Moon, and 'the derivation of the mean and true planets'. • Mathurānātha Śarman (1609 CE): Author of Ravisiddhāntamañjarī or Sūryasiddhāntamañjarī • Pathani Samanta (1835–1904 ) the last in chain of naked eye astronomers of India belonging to Siddhantic Era. Was born in Kahndapada, a feudatory state of Odisha. He studied various Siddhantas and found them to be erroneous as the planets were either not found at the right places or at right time. He made more studies, observed deeply and made several instruments to perfect his analysis of his observation. He composed his findings into a voluminous treatise name Siddhanta Darpan giving new formulaes to predict celestial occurrences. His almanac was adopted by the Jagannath Temple of Puri. He was awarded the title of Mahamahopadhyaya by the Viceroy of India Mr.Lansdowne and also a title Harichandan Mahapatra by Gajapati King of Puri. The instruments designed by him were for measurement of time and position of stellar bodies and were named Chapa Yantra, Mana Yantra, Golardha Yantra, Dhanu Yantra, Chakra Yantra, Swayambha Yantra, Gola Yantra etc. A postage stamp has been issued by the government of India in his honor. ==Instruments used==

(1688–1743 CE) initiated the construction of several observatories. Shown here is the Jantar Mantar (Jaipur) observatory. (completed by 1743 CE), Delhi. . Among the devices used for astronomy was gnomon, known as Sanku, in which the shadow of a vertical rod is applied on a horizontal plane in order to ascertain the cardinal directions, the latitude of the point of observation, and the time of observation. This device finds mention in the works of Varāhamihira, Āryabhata, Bhāskara, Brahmagupta, among others. The Cross-staff, known as Yasti-yantra, was used by the time of Bhaskara II (1114–1185 CE). The Goladīpikāa detailed treatise dealing with globes and the armillary sphere was composed between 1380 and 1460 CE by Parameśvara. ==International discourse==

, Ai-Khanoum, Afghanistan 3rd–2nd centuries BCE Indian and Greek astronomy According to David Pingree, there are a number of Indian astronomical texts dated to the sixth century CE or later with a high degree of certainty. There is substantial similarity between these and pre-Ptolemaic Greek astronomy. Pingree believes that these similarities suggest a Greek origin for certain aspects of Indian astronomy. One of the direct proofs for this approach is the fact quoted that many Sanskrit words related to astronomy, astrology and calendar are either direct phonetic borrowings from the Greek language, or translations, assuming complex ideas, like the names of the days of the week which presuppose a relation between those days, planets (including Sun and Moon) and gods. With the rise of Greek culture in the east, Hellenistic astronomy filtered eastwards to India, where it profoundly influenced the local astronomical tradition. Numerous interactions with the Mauryan Empire, and the later expansion of the Indo-Greeks into India suggest that transmission of Greek astronomical ideas to India occurred during this period. The Greek concept of a spherical Earth surrounded by the spheres of planets, further influenced the astronomers like Varahamihira and Brahmagupta. Several Greco-Roman astrological treatises are also known to have been exported to India during the first few centuries of the present era. The Yavanajataka is a Sanskrit text of the 3rd century CE on Greek horoscopy and mathematical astronomy. Later in the 6th century, the Romaka Siddhanta ("Doctrine of the Romans"), and the Paulisa Siddhanta ("Doctrine of Paul") were considered as two of the five main astrological treatises, which were compiled by Varāhamihira in his Pañca-siddhāntikā ("Five Treatises"), a compendium of Greek, Egyptian, Roman and Indian astronomy. Varāhamihira goes on to state that "The Greeks, indeed, are foreigners, but with them this science (astronomy) is in a flourishing state." However, the most detailed incorporation of Indian astronomy occurred only during the Tang dynasty (618–907 CE) when a number of Chinese scholarssuch as Yi Xingwere versed both in Indian and Chinese astronomy. Another Indian influence was an approximate formula used for timekeeping by Muslim astronomers. Through Islamic astronomy, Indian astronomy had an influence on European astronomy via Arabic translations. During the Latin translations of the 12th century, Muhammad al-Fazari's Great Sindhind (based on the Surya Siddhanta and the works of Brahmagupta), was translated into Latin in 1126 and was influential at the time. Indian and Islamic astronomy Many Indian works on astronomy and astrology were translated into Middle Persian in Gundeshapur, the Sasanian Empire, and later translated from Middle Persian into Arabic. In the 17th century, the Mughal Empire saw a synthesis between Islamic and Hindu astronomy, where Islamic observational instruments were combined with Hindu computational techniques. While there appears to have been little concern for planetary theory, Muslim and Hindu astronomers in India continued to make advances in observational astronomy and produced nearly a hundred Zij treatises. Humayun built a personal observatory near Delhi, while Jahangir and Shah Jahan were also intending to build observatories but were unable to do so. After the decline of the Mughal Empire, it was a Hindu king, Jai Singh II of Amber, who attempted to revive both the Islamic and Hindu traditions of astronomy which were stagnant in his time. In the early 18th century, he built several large observatories called Yantra Mandirs, to rival Ulugh Beg's Samarkand observatory and to improve on the earlier Hindu computations in the Siddhantas and Islamic observations in Zij-i-Sultani. The instruments he used were influenced by Islamic astronomy, while the computational techniques were derived from Hindu astronomy. Indian astronomy and Europe Some scholars have suggested that knowledge of the results of the Kerala school of astronomy and mathematics may have been transmitted to Europe through the trade route from Kerala by traders and Jesuit missionaries. such as communication routes and a suitable chronology certainly make such a transmission a possibility. However, there is no direct evidence by way of relevant manuscripts that such a transmission took place. In the early 18th century, Jai Singh II of Amber invited European Jesuit astronomers to one of his Yantra Mandir observatories, who had bought back the astronomical tables compiled by Philippe de La Hire in 1702. After examining La Hire's work, Jai Singh concluded that the observational techniques and instruments used in European astronomy were inferior to those used in India at the time – it is uncertain whether he was aware of the Copernican Revolution via the Jesuits. He did, however, employ the use of telescopes. In his Zij-i Muhammad Shahi, he states: "telescopes were constructed in my kingdom and using them a number of observations were carried out". Following the arrival of the British East India Company in the 18th century, the Hindu and Islamic traditions were slowly displaced by European astronomy, though there were attempts at harmonising these traditions. The Indian scholar Mir Muhammad Hussain had travelled to England in 1774 to study Western science and, on his return to India in 1777, he wrote a Persian treatise on astronomy. He wrote about the heliocentric model, and argued that there exists an infinite number of universes (awalim), each with their own planets and stars, and that this demonstrates the omnipotence of God, who is not confined to a single universe. The last known Zij treatise was the Zij-i Bahadurkhani, written in 1838 by the Indian astronomer Ghulam Hussain Jaunpuri (1760–1862) and printed in 1855, dedicated to Bahadur Khan. The treatise incorporated the heliocentric system into the Zij tradition. ==Schools and organisations of astronomy==

Jantar Mantar Jantar (means yantra, machine); mantar (means calculate). Jai Singh II in the 18th century took great interest in science and astronomy. He made various Jantar Mantars in Jaipur, Delhi, Ujjain, Varanasi and Mathura. The Jaipur instance has 19 different astronomical calculators. These comprise live and forward-calculating astronomical clocks (calculators) for days, eclipses, visibility of key constellations which are not year-round northern polar ones thus principally but not exclusively those of the zodiac. Astronomers abroad were invited and admired complexity of certain devices. (completed by 1743 CE), Delhi. As brass time-calculators are imperfect, and to help in their precise re-setting so as to match true locally experienced time, there remains equally his Samrat Yantra, the largest sundial in the world. It divides each daylit hour as to solar 15-minute, 1-minute and 6-second subunits. Other notable include: • Nadivalaya yantra • Rama Yantra • Daksinottara Bhitti • Unnatamsha Yantra • Jai Prakash yantra Kerala school of astronomy and mathematics Models of the Kerala school (active 1380 to 1632) involved higher order polynomials and other cutting-edge algebra; many neatly were put to use, principally for predicting motions and alignments within the Solar System. ==20th and 21st Century==

Astronomers During 1920, astronomers like Sisir Kumar Mitra, C.V. Raman and Meghnad Saha worked on various projects such as sounding of the ionosphere through ground-based radio and the Saha ionisation equation. Homi J. Bhaba and Vikram Sarabhai made significant contributions. Vainu Bappu considered father of modern Indian astronomy and Govind Swarup considered father of radio astronomy in India initiated development of modern astronomical observatories that placed India astronomy in the world map. A. P. J. Abdul Kalam also known as Missile Man of India assisted in development and research for the Defence Research and Development Organisation and the Indian Space Research Organisation's (ISRO) civilian space programme and launch vehicle technology. Organizations Madras Observatory, established in 1786, was the first observatory on Indian soil equipped with modern telescopes, photographic plates and spectrographs. It played a significant role in the discovery of Helium, in the solar spectrum, during the solar eclipse. In 1899 it was relocated and evolved to form the Kodaikanal Solar Observatory. In 1971, it evolved again to form the Indian Institute of Astrophysics in Bangalore becoming a large organisation dedicated to research in astronomy and astrophysics. Nizamiah/Osmania Observatory (Estd. 1900 ) and Uttar Pradesh State Observatory (Estd. 1951), which later moved from Lucknow to Nainital and became Aryabhatta Research Institute for Observational Sciences (ARIES) were two other early astronomical organisations to initiate modern astronomical research in India. Bhaba established the Tata Institute of Fundamental Research and Vikram Sarabhai established the Physical Research Laboratory. These organisations researched cosmic radiation and conducted studies of the upper atmosphere. In 1950, the Department of Atomic Energy was founded with Bhaba as secretary and provided funding to space researches in the country. The Indian National Committee for Space Research (INCOSPAR) was founded in 1962 on the urging of Sarabhai. ISRO succeeded INCOSPAR and the Department of Space (under Indira Gandhi) was established, thereby institutionalising astronomical research in India. Organisations like SPARRSO in Bangladesh, SUPARCO in Pakistan and others were founded shortly after. Ooty Radio Telescope, constructed in 1970, gave rise to radio astronomy observatories in India. It is still the largest, fully steerable, cylindrical radio telescope in the world. The team grew big and by the year 2000 built the Giant Meterwave radio Telescope, the largest such radio telescope in the world. The power and versatility of GMRT attracts astronomers from all over the world, to use it free of cost, and contribute towards the advancement of human knowledge about space and Universe. Space programmes and research • ISRO played a role in the discovery of three species of extremophile bacteria in the upper stratosphere at an altitude between 20–40 km which are highly resistant to ultra-violet radiation, which are named as Bacillus isronensis, Bacillus aryabhattai (in recognition of ISRO's contribution) and Janibacter hoylei. • Astrosat, a space observatory launched in 2015 by ISRO, detected a gamma-ray burst in January 2017, captured a rare phenomenon of a 6-billion-year-old blue straggler feeding off and sucking out mass and energy out of a bigger star and detected a rare X-ray outburst in a Be/X-ray binary system RX J0209.6-7427. • Chandrayaan-3 is the third mission in the Chandrayaan programme, a series of lunar-exploration missions developed by the ISRO. It objectivized to conduct soft landing on Lunar south pole, observing & demonstrating the rover's driving capabilities on the Moon and conducting experiments on the materials available on the lunar surface to better understand the composition of the Moon. The launch was done on 14 July 2023 at the Satish Dhawan Space Centre. The lander and rover successfully landed at the south pole of moon on 23 August 2023. ==See also==