Rathasapthami is the ritual observed in the Tamil month of Thai (Maga) on the seventh day from Amavasya. Ratha means the chariot, (the chariot of the Sun) and Sapthami is the thithi that falls on the seventh day in Sukla Paksha after Amavasya.
The chariot of the Sun is drawn by seven horses denoting the energy and force of the Sun God and the thithi ‘sapthami’ signifies the energy of the Sun with his chariot drawn by
seven horses, since it is the seventh day from Amavasya. Seven also denotes the seven days of a week and a week starts with Sunday. It is also said that seven denotes seven colours of the rainbow. There are 12 wheels in the chariot that shows the 12 zodiac signs and also 12 months in a year.
Rathasapthami is noted for the Uttarayana kalam in which it is observed. It signifies the energetic journey of the Sun in the northern hemisphere as he has moved to the house of Saturn, Capricorn from Dhanush. This transit of the Sun is the harbinger of warm days and spring season after the bitter cold of the winter days. It showcases energy and activity and thus Rathasapthami is celebrated to commemorate the increased atmospheric warmth and energy through the transit of the Sun. Lord Vishnu is also worshipped on this day.
Rathasapthami is considered as the birth day of the Sun and thus is celebrated as Surya Jayanthi in many places of India. It is also the time Bhishma breathed his last.
Having a holy bath in the morning and reciting prayers and slokas like Surya Astothram, Adithya Hridhayam, Suryashtakam and offering milk as neivedyam is the way people observe Rathasapthami.
People keep 7 arga (erruku) leaves with akshadhai (rice mixed with turmeric) while taking bath chanting the following sloka.
Sapta Sapti Priye Devi Sapta Loka Pradeepike;
Sapta janmaarjitam paapam hara saptami satvaram
Etatjanma krutam paapam krutam sapta sujanmasoo
Naumi saptami Devitwaam sapta lokaika Maataram
Saptaarga patra snaane mama paapam Vyopahayae
With this sloka, people pray to Sun God while bathing to relieve us of our sins committed during our seven births.
Afterr bath, we offer surya argyam (jala tarpanam) with water and offer milk as neivedyam to Sun God. Arghyam is offered to the Sun with the following mantra
Saptasaptivaha! preetah ! saptaloka pradeepana,
Saptameesahito deva !gruhaanaarghyam divaakara! ''
Erruku reflects the energy of the Sun and keeping it on our forehead will increase our energy. It is called ‘arka’ in Sanskrit, which is synonymous with the name of Sun God. Erruku is as sacred to the Sun as tulsi is to Lord Vishnu.
There was a story narrated by Kamboj’s king Yashovarma about a king who had no heir for a long time. After lots of prayers, he was blessed with a son. But, the son was terminally ill and as per the advice of a saint, the son performed Rathasapthami Pooja to get rid of his sins and got cured of his illness.
Bhishma waited for 48 days on the arrow bed for the arrival of Uttarayana kalam and breathed his last on the Ashtami which was the next day to RathaSapthami. He waited for the transit of the Sun from Dhanush to Makara rasi. People perform tarpan to Bhishma on Rathasapthami to pay homage to such a great soul.
So, by praying to the Sun God on Rathasapthami, one is able to get rid of his sins done in seven births and gets energised for the ongoing life activities.