Ratha Sapthami is a very auspicious day in the Hindu calendar. The Sun god travels in the north and south directions in a year. These are called Uttarayanam(the first half of the year) and Dakshinayanam(the second half of the year). The first half is considered most auspicious than the second half of the year. This is the day that Surya was born to sage Kashyapa and his wife Adithi.
Surya is considered as an important god because he is the source of life. Thats why he is placed in the center of navagrahas (nine planets). Scientists found out that sun is the center of all nine planets and all of them orbit around the sun. Our sages found out this truth thousands of years ago and mentioned at several places in the Hindu scriptures. In fact, the characteristics of the sun and all the nine planets have been clearly described in the Vedas. One can identify these characteristics in the navagraha manthra, and are similar to what the NASA scientist described in their research findings. This is a great testimony to state that many aspects of Hindu faith are scientifically important.
Being the center of all planets Surya Deva is called as graharaja (the king of planets). He rides on a chariot that is pulled by seven white horses, which are the seven rainbow colors, and his movement is nothing but the time that gives meaning to our lives. Surya deva goes with several names such as Aditya, Ravi, Bhaskara, Arka, Diwakara, etc. According the Hindu scriptures Lord Vishnu (the proprietor of this Universe) created thousands of gods for different jobs for the smooth functioning of the universe. Theses gods who are responsible for different jobs are called as demi gods. Surya Devs job is to provide necessary sunlight to the universe so that the life may sustain on them.
Many people worship Surya because he is called as Aarogya and Aishwarya Datha (provider of health and wealth). Surya is worshipped early in the morning while fresh sunrays emerge. It is believed and proven that exposure to fresh sunrays rejuvenate energy, and purify the mind and body. Thats why many Hindus do suryanamaskaras (12 postures of prostrating to Surya) early morning when sunrays are fresh. Scientifically also it is recommended that there are many benefits of getting exposed to early morning sun.
Vedas provided us with sthothras like Aditya Hridayam, Surya Ashtakam, Surya Shathakam, etc. and reciting them will bring lot of benefits to people in terms health, wealth and success. In Taittareeya Aaranyakam there is Aruna Prashna which is one of the powerful chantings associated with praying Surya. In fact, sage Agasthya advised Lord Rama to worship Surya to win the war against Ravana. Sage Agasthya gives Lord Rama Aditya Hridayam upadesha(teaches) before the war began and Suryas energy helped Lord Rama to overcome the demonic power of Ravana. Thats why recitation of Aditya Hridayam daily or at least on Sunday gives people the benefits of health, wealth and success.
Brahmanas and all those who have Yajnopaveetham(sacred thread) must perform Sndhya Vandanam in the morning, afternoon and evening everyday. In addition to worshipping goddess Gayathri, an important component of Sandhyavandanam is to offer water to Surya(Arghya Pradanam) to give energy to him to sustain throughout the day and fight back demons and in the night to reappear again the next day.
It is highly recommended that one should pray to Surya Dev on Ratha Sapthami day by reciting or listening or chanting Aditya Hridayam, Surya Ashtakam, Surya Shathakam, Aruna Parayanam, Vedam, and performing Surya namaskarams early in the morning. Further, praying to Surya everyday or at least Sunday is highly recommended for good health, wealth and also to take away any obstacles in life.