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Sundial, calendar and Khmer temples
Astro-archaeology = Astroarchaeology

Sunrises and sunsets at Prasat Phanom Rung in 2010

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Nandin fronting Shiva, the lingam, and the setting sun.
 (See as high-resolution at NARIT)

INTRODUCTION
The astronomical aspects of Prasat Phanom Rung are:
• 1. Solar: The illumination of the linga occurring close to 14 days before and after the two equinox days. Annually there are 4 solar events. At each event the sun will be visible the day before and after as well. On each day the sun will be visible for some 8 minutes.
• 2. Solar-lunar: The period from the solar event before equinox to the event after equinox is close to one sidereal lunar month (27.3 days). The moon will be located at the same location (zodiacal sign, naksatra) at both events.
• 3. Eclipses: When a solar or lunar eclipse occurs at a solar event it will most likely be repeated with some interval at a coming solar event.

(Ref.: Solar-lunar events at Prasat Phanom Rung in Spring 2007 AD. Muang Boran Journal, May 2007, by Asger Mollerup).


Sunset through all 15 doors

1. Solar events (sunrises and sunsets)

Sunsets in March 2010:

5th of March at 18:15:47
6th of March at 18:15:58
7th of March at 18:16:09
Fig 1: Observed from centre line,
mid-door, 7 m outside the eastern door.
 		   Fig 2: Observed from centre line,
threshold, 7 m outside the eastern door.
 

Sunrises in April 2010:

2nd of April: Sunrise at 06:04:46
3rd of April: Sunrise at 06:04:04
4th of April: Sunrise at 06:03:22
 
Fig 3: Observed from centre line,
mid-door, 7.5 m outside the western door.
 		   Fig 4: Observed from centre line,
threshold, 7.5 m outside the western door.
 

 

Sunrises in September 2010:

9th of September: Sunrise at 05:57:52
10th of September: Sunrise at 05:57:55
11th of September: Sunrise at 05:57:58
Fig 5: Observed from centre line,
mid-door, 7.5 m outside the western door.
 

 

 Fig 6: Observed from centre line,
threshold, 7.5 m outside the western door.
 

 

Sunsets in October 2010:

6th of October: Sunset at 17:53:20
7th of October: Sunset at 17:52:38
8th of October: Sunset at 17:51:57
Fig 7: Observed from centre line,
mid-door, 7 m outside the eastern door.
 

 

 Fig 8: Observed from centre line,
threshold, 7 m outside the eastern door.
 

Bold text marks the days when the sun rises or sets the closest to the centre of the 15-doorways. The times given are when the sun is 50% visible at the mathematical horizon (Ref.: Astronomic Clock).
 

 

2. Solar-lunar events: Naksatra (lunar houses)

 
Fig. 9: Two hours after sunset 6th March 2010 the moon will be located in the zodiacal sign Scorpius.
 		   Fig. 10: Two hours before sunrise 3rd April 2010 the moon will have returned to the same location in Scorpius - between the claws of the Scorpion.


     The moon changes position every night when compared with the stars. After one (sidereal) lunar month the moon will have passed all 12 zodiacal signs and have returned to its starting point - as illustrated above.
     The celestial sphere can be divided into 12 solar houses, the zodiacal signs - or into 27 lunar houses, the naksastras. The ancient Khmers would for calendric and astrological reasons have paid more attention to the latter.

 

3. Solar and lunar eclipses

     There will be a partial solar eclipse in the afternoon the 15th of January 2009 when the sun will be 55% eclipsed (see photo below) - and not related to the solar-lunar events at Phanom Rung.
     The 26th of June the moon will be 51% eclipsed as it rises shortly after sunrise.

     There will be no eclipses around any of the solar-lunar events at Prasat Phanom Rung.
     Rahu and Ketu (right) will so to speak be absent in 2010...
Fig. 11: Rahu and Ketu.
Rahu seizing the moon

 

4. Other celestial events around the sunrise on 3rd April 2010

     At dawn Jupiter will be visible on the eastern sky: Jupiter will rise at 04:44.
     The planet Jupiter is associated with Indra who is also the leader of the guardians of the cardinal directions, the dikpala, and depicted towards the rising sun on many Khmer temples. Indra rides on his elephant, Airavata, carrying the thunderbolt, the vajra, in his right hand (right, Prasat Phanom Rung).
 

 

5. Shivaratri

     Shivaratri, ‘the night of Shiva’, is related to astronomy by being celebrated the night when the crescent moon is visible before sunrise for the last time before new moon, the 13th or 14th night of Krishna Paksa, the waning fortnight of the lunar month (right: The crescent moon 8 November 2007, two days before new moon).
     The crescent moon is one of Shiva’s symbols and often depicted on statues in his matted hair (right: Shiva in Bakheng style. Not my photo).

     Every lunar month has a Shivaratri, but the most important for Shiva and shivaites is the Maha Shivaratri (‘the Great Night of Shiva’) in the lunar month Magha. In 2010 Magha spans from 16 January to 14 February and Maha Shivaratri will in India be celebrated the 12th of February 2010 by offerings of bael leaves to Shiva, all day fasting and an all night long vigil.
     In the following lunar month, Phalguna, Shivaratri is 13 March. Neither of the two events will be celebrated at Prasat Phanom Rung.

     In autumn 2010 Shivaratri will be the 6th of September and the 6th of October. The first is two days before the lunar-solar events at Prasat Phanom Rung; the latter coincides with the first of the three days when the sun sets aligned with the 15 door-ways of Prasat Phanom Rung.


 

Above: 5th of March 2009 Above: 6th of March 2009 Above: 7th of March 2009

 

External links:
 
 
National Astronomical Research Institute of Thailand (NARIT):
1. Astronomy and World Heritage: Prasat Phanom Rung is considered as a candidate for a Thai Astronomical Landmark. NARIT conducted an informal on site seminar on “Astronomical Wonders of  Prasat Phnom Rung” the 7th of March 2009 and plans to held another in Chiang Mai in 2010 on the subject of astro-archaeology in Thailand.
2. About the seminar 7th of March 2009: In Thai
3. NARIT's annual Astrophotography Contest with my photo of the bull Nandin, Shiva's vehicle, watching Sunset behind Linga photo.
The Ministry of Science and Technology: NARIT's Astrophotography Contest (in Thai)
Muang Boran Journal: Solar-lunar events at Prasat Phanom Rung in Spring 2007 AD, by Asger Mollerup, printed in Bangkok, 2007. In Thai and English.
 

 

 

APPENDIX:

      
     
  Pictures above: Sunrise at Prasat Sdok Kok Thom, Sra Kaeo Province, at spring equinox 2009.  
 


     Nearly all Khmer temples are orientated so that the rays of the rising sun enters the eastern doors twice a' year. The largest group is orientated 90 degrees true east resulting in that the solar events happen at equinox - as at Prasat Sdok Kok Thom. Other temples with other orientations will have solar events on other dates.

     I will hereafter present one new location for the public each year. In 2010 I will go for Prasat Khao Lon in Sra Kaeo Province which is located on a small mountain and build in 1006 AD. And inscription mentions Suryavarman I, 'the king of the four sacred doors' and indicates the exact day  when the temple was consecrated.

Z

2 December 2009

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All photos, calculations and drawings © Asger Mollerup

(Independent consultant on astro-archaeology and surveyor on Khmer temples at Buriram Provincial Office)