The sun, in both its
physical and anthropomorphic forms as a celestial phenomena.
Since the Vedas, the oldest and most authoritative Hindu
religious literature, the sun has been an important god and has maintained a
position of considerable prominence.
The Gayatri Mantra, for example, is a holy mantra that is
supposed to be sung every day by twice-born males, or men from the three
"twice-born" groups—brahmin, kshatriya, and vaishya—who have
completed the teenage religious initiation known as "second birth."
Invoking the sun as the creator and nourisher of all things, the Gayatri Mantra
asks him to awaken the brains of all who observe him.
Many Smarta brahmins continue to worship Surya as one of the
"five-fold" (panchayatana) deities (the others being Shiva, Vishnu,
the Goddess, and Ganesh), according to the Advaita philosopher Shankaracharya.
Surya was also the dominant god for various groups, notably
in eastern India, for a period, but his devotion has since been substantially
superseded.
The temple of the sun at Konarak (now damaged) is the most
impressive example of pagan devotion, with its immense size and abundance of
sensual sculptures on its external walls.
Religious Beliefs and Practices of North India During the
Early Medieval Period, by Vibhuti Bhushan Mishra, 1973; and Sarat Chandra
Mitra, The Cult of the Sun God in Medieval Eastern Bengal, 1986.
You may also want to read more about Hinduism here.
Be sure to check out my writings on religion here.