Which ancient Indian astronomer wrote the 'Aryabhatiya'?

The ancient Indian astronomer who wrote the Aryabhatiya was Aryabhata. Composed in Sanskrit, the work is his best-known surviving treatise on mathematics and astronomy.

Aryabhata was born in 476 CE and became one of the leading scholars of India’s classical mathematical tradition. The Aryabhatiya presents technical ideas in compact verse, covering arithmetic, geometry, algebra, timekeeping, trigonometry, and planetary motion. Its four sections are commonly known as Gitikapada, Ganitapada, Kalakriyapada, and Golapada.

The treatise describes a place-value numeration system, gives a table of sines, and discusses methods for calculating astronomical positions. Aryabhata also argued that the apparent daily movement of the stars could be explained by Earth’s rotation, an unusually important insight for its era. He calculated an approximation of pi and addressed eclipses using a naturalistic astronomical model.

Bhaskara, Brahmagupta, and Varahamihira were important later Indian scholars, but none wrote the Aryabhatiya. Bhaskara I, in particular, wrote a major commentary on Aryabhata’s text, which is why the two names are sometimes confused.