Grahana (ग्रहणम्)

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परिचयः ॥ Introduction

Eclipses have been expressed by the notion of Rahu or Svarbhanu seizing the heavenly body. The Ṛgveda (5. 40. 5–9) describes an eclipse of the Sun as brought about by Svarbhānu.

यत्त्वा सूर्य स्वर्भानुस्तमसाविध्यदासुरः । अक्षेत्रविद्यथा मुग्धो भुवनान्यदीधयुः ॥५॥

स्वर्भानोरध यदिन्द्र माया अवो दिवो वर्तमाना अवाहन् । गूळ्हं सूर्यं तमसापव्रतेन तुरीयेण ब्रह्मणाविन्ददत्रिः ॥६॥

मा मामिमं तव सन्तमत्र इरस्या द्रुग्धो भियसा नि गारीत् । त्वं मित्रो असि सत्यराधास्तौ मेहावतं वरुणश्च राजा ॥७॥

ग्राव्णो ब्रह्मा युयुजानः सपर्यन्कीरिणा देवान्नमसोपशिक्षन् । अत्रिः सूर्यस्य दिवि चक्षुराधात्स्वर्भानोरप माया अघुक्षत् ॥८॥

यं वै सूर्यं स्वर्भानुस्तमसाविध्यदासुरः । अत्रयस्तमन्वविन्दन्नह्यन्ये अशक्नुवन् ॥९॥

The Tāṇḍya-brāhmaṇa mentions eclipses as many as five times.

स्वर्भानुर्व्वा आसुर आदित्यन्तमसाविध्यत्तस्य देवा दिवाकीर्त्यैस्तमोपाघ्नन्यद्दिवाकीर्त्यानि भवन्ति तम एवास्मादपघ्नन्ति रश्मयो वा एत आदित्यस्य यद्दिवाकीर्त्यानि रश्मिभिरेव तदादित्यं साक्षादारभन्ते || 4. 6. 13||

स्वर्भानुर्व्वा आसुर आदित्यन्तमसाविध्यत्तं देवा न व्यजानंस्तेत्रिमुपाधावंस्तस्यात्रिर्भासेन तमोपाहन्यत् प्रथममपाहन् सा कृष्णाविरमवद्यद्वितीयं सा राजता यत्तृतीयं सा लोहिनी यया वर्णमय्यतृणत् सा शुक्लासीत् ||6. 6. 8||

And in 4. 5. 2; 14. 11. 14–15; 23. 16. 2 Eclipses have been mentioned in the Atharvaveda (19. 9. 10)

शं नो ग्रहाश्चान्द्रमसाः शमादित्यश्च राहुणा । शं नो मृत्युर्धूमकेतुः शं रुद्रास्तिग्मतेजसः ॥१०॥

the Gopathabrāhmaṇa (8. 19) and the Śatapatha-brāhmaṇa (5. 3. 2. 2) also.

स्वर्भानुर्ह वा आसुरः । सूर्यं तमसा विव्याध स तमसा विद्धो न व्यरोचत तस्य सोमारुद्रावेवैतत्तमोऽपाहतां स एषोऽपहतपाप्मा तपति तथो एवैष एतत्तमः प्रविशत्येतं वा तमः प्रविशति यदयज्ञियान्यज्ञेन प्रसजत्ययज्ञियान्वा एतद्यज्ञेन प्रसजति शूद्रांस्त्वद्यांस्त्वत्तस्य सोमारुद्रावेवैतत्तमोऽपहतः सोऽपहतपाप्मैव दीक्षते तद्यच्छ्वेतायै श्वेतवत्सायै पयसि शृतो भवति कृष्णं वै तमस्तत्तमोऽपहन्ति तस्यैषैव श्वेता श्वेतवत्सा दक्षिणा - ५.३.२.[२]

ग्रह m. seizure of the sun and moon , eclipse AV. xix , 9 , 7 and 10 VarBr2S.

Apte

an eclipse; शशिदिवाकरयोर्ग्रहपीडनम् Bh.2.91; H.1.51; Pt.2.19.-पुषः the sun. -भक्तिः f. division of countries &c. with respect to the presiding grahas (ग्रहाः).

Eclipse in Aryabhatasiddhanta

Prof K. S. Shukla, in his paper titled 'Aryabhata I's astronomy with midnight day-reckoning' adduced concrete and conclusive evidence to show that Aryabhata I, the celebrated author of the Aryabhatiya, wrote one more work on astronomy which was known as Aryabhatasiddhanta. This work of Aryabhata that adopted midnight day reckoning, meaning, where the day was reckoned from one midnight to the next, was mentioned by many later scholars including, Mallikarjuna Suri (1178 AD) of Vengi in Andhra.

Mallikarjuna Suri enumerates the possibility of an eclipse as discussed in the Aryabhatasiddhanta as follows:

Total or Partial Eclipse

Adding 6 signs to the Sun at a parva (full moon or new moon), one gets the Earth’s shadow. This is the eclipser of the Moon.

• When it is equal to the Moon’s node, we have a total eclipse of the Moon.
• If the Moon’s latitude corrected for parallax happens to be zero at that time, we have a total solar eclipse.
• When the Moon’s latitude exists, if the parallax in latitude is less than half the sum of the diameters of the eclipsed and eclipsing bodies, a partial eclipse of the Sun will be possible .

Possibility of a Solar Eclipse

A solar eclipse is possible when,

1. The equinoctial midday shadow is 1 digit and the distance of the Earth’s shadow or the Sun from the Moon’s ascending node is less than 14 degrees.
2. The equinoctial midday shadow is 5 digits and the distance of the Earth’s shadow or the Sun from the Moon’s ascending node is less than 16 degrees.

Possibility of a Lunar Eclipse

A lunar eclipse is possible when,

1. The distance of the Shadow or the Sun from the Moon's node is less than 12 degrees and the Moon’s velocity greater than 12 degrees 20′, then there is a possibility of a lunar eclipse.
2. The distance of the Shadow or the Sun from the Moon's node is less than 13 degrees and the Moon’s velocity greater than 13 degrees 20′.

Negation of a Solar Eclipse

A solar Eclipse does not occur if,

1. The Moon’s latitude is zero when the parallax in latitude amounts to half the sum of the eclipsed and eclipsing bodies.
2. The Moon’s latitude (at new Moon) is zero when the parallax in latitude is equal to or greater than half the sum of the diameters of the eclipsed and eclipsing bodies.
3. The equinoctial midday shadow is 1 digit and the distance of the Earth’s shadow or the Sun from the Moon’s ascending node amounts to 14 degrees.
4. The equinoctial midday shadow is 5 digits and the distance of the Earth’s shadow or the Sun from the Moon’s ascending node is 16 degrees.

Negation of a Lunar Eclipse

A lunar eclipse does not occur when,

1. The distance of the Shadow or the Sun from the Moon’s node is 12 degrees and also if the Moon’s velocity per day amounts to 12 degrees 20′.
2. The distance of the Shadow or the Sun from the Moon’s node is 13 degrees and the Moon’s velocity 13 degrees 20′.
3. The distance of the Shadow or the Sun from the Moon’s ascending node exceeds 14 degrees and the Moon’s velocity is 14 degrees 20′.
4. The distance of the Shadow or the Sun from the Moon’s node is 14 degrees. In that case, the Moon’s velocity does not play any role.

Observations

1. At places where the equinoctial midday shadow is 1 digit, parallax in latitude is always less than half the sum of the eclipsed and eclipsing bodies.
2. At places where the equinoctial midday shadow is 5 digits, the parallax in latitude is sometimes less and sometimes equal to half the sum of the diameters of the eclipsed and eclipsing bodies.
3. At places where the equinoctial midday shadow is 9 digits, the parallax in latitude is sometimes less than, sometimes equal to, and sometimes greater than half the sum of the diameters of the eclipsed and eclipsing bodies.
4. One should proceed to calculate a lunar eclipse only when the distance of the Shadow or the Sun from the Moon's node is less than 14 degrees.
5. In a place where the equinoctial midday shadow is 9 digits and the Sun is at the last point of the sign Gemini, the length of the day amounts to 36 ghatis; and when at the end of the sign Sagittarius, the day amounts to 24 ghatis.
6. Where the equinoctial midday shadow exceeds 9 digits, there is no habitation. Hence, knowledge of occurrence of eclipses for those places is of no use. For, people do not live beyond 600 yojanas from the equator. The region lying north of that is inaccessible to man.

Tamma Yajva and Ramakrshna Aradhya too have included the above discussion of the possibility of an eclipse in their commentaries on the Suryasiddhanta.