Surya, the sun-god, controls the affairs of the entire universe, especially in regard to heat, light, seasonal changes and so on. He is considered to be an expansion of Narayana and is sometimes called Surya Narayana.
Surya represents the three Vedas -- Rg, Yajur and Sama -- and therefore he is known as Trayimaya, the form of Lord Narayana. Surya is also called Diakara (day- maker), and Grahapati (king of the planets).
The sun-god has expanded himself in twelve divisions, and thus he controls the six seasonal changes and causes winter, summer, rain and so on.
The sun-god, who is Narayana, or Visnu, the soul of all the worlds, is situated in outer space between the upper and lower portions of the universe. Passing through twelve months on the wheel of time, the sun comes in touch with twelve different signs of the zodiac and assumes twelve different names according to those signs. The aggregate of those twelve months is called a samvatsara, or an entire year. According to lunar calculations, two fortnights -- one of the waxing moon and the other of the waning -- form one month. That same period is one day and night for the planet Pitrloka. According to stellar calculations, a month equals two and one quarter constellations. When the sun travels for two months, a season passes, and therefore the seasonal changes are considered parts of the body of the year.
The entire kala-cakra, or wheel of time, is established on the wheel of the sun-god's chariot. This wheel is known as Samvatsara. The seven horses pulling the chariot of the sun are known as Gayatri, Brhati, Usnik, Jagati, Tristup, Anustup and Pankti. They are harnessed by a demigod known as Arunadeva to a yoke 900,000 yojanas wide. Thus the chariot carries Adityadeva, the sun-god. Always staying in front of the sun-god and offering their prayers are sixty thousand sages known as Valikhilyas. There are fourteen Gandharvas, Apsaras and other demigods, who are divided into seven parties and who perform ritualistic activities every month to worship the Supersoul through the sun-god according to different names. Thus the sun-god travels through the universe for a distance of 95,100,000 yojanas (760,800,000 miles) at a speed of 16,004 miles at every moment.
Bhaktivedanta Book Trust. Excerpted from various sources, including text and Purports of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.
Painting is from the collection of St. Petersburg Institute of Oriental Studies.