Budha
Budha is the Sanskrit word for the planet Mercury, personified as the god of intelligence.
He is also known as Somaya or Rohinaya. He rules over the nakshatras of Ashlesha, Jyeshtha, and Revati.
Planet
Indian astronomical observations of the planet Budha are recorded in Sanskrit texts such as the 5th century CE Aryabhatiya by Aryabhata, the Romaka by Latadeva and Panca Siddhantika by Varahamihira from the 6th century, Khandakhadyaka by Brahmagupta from the 7th century, and the Sisyadhivrddida by Lalla from the 8th century. These texts describe the characteristics of planetary motion. Other texts such as Surya Siddhanta, thought to have been completed between the 5th century CE and 10th century CE, present information on various planets along with the mythologies of their associated gods.Different manuscripts of these texts vary slightly in their measurements of Budha's revolutions, apogee, epicycles, nodal longitudes, orbital inclination, and other parameters, suggesting that the texts were open and revised over the years. For example, both Khandakhadyaka and Surya Siddhanta of Varaha state that Budha completes 17,937,000 revolutions on its own axis every 4,320,000 years, and had an apogee of 220 degrees in 499 CE; while another manuscript of Surya Siddhanta increases the revolutions by 60 to 17,937,060, and the apogee to 220 degrees and 26 seconds.
Hindu scholars of the 1st millennium CE estimated the time it took for sidereal revolutions of each planet including Budha, from their astronomical studies, with slightly different results:
| Source | Estimated time per sidereal revolution |
| Surya Siddhanta | 87 days, 23 hours, 16 minutes, 22.3 seconds |
| Siddhanta Shiromani | 87 days, 23 hours, 16 minutes, 41.5 seconds |
| Ptolemy | 87 days, 23 hours, 16 minutes, 42.9 seconds |
| 20th century calculation | 87 days, 23 hours, 15 minutes, 43.9 seconds |
Legends
Budha is a god in Hindu mythology and is the son of Chandra and Rohini or Tara. The events leading to his birth from the latter is detailed in the myth of the Tarakamaya War. Budha has a son, the king Pururavas, with his wife Ila.One of the earliest mentions of Budha appears in the Vedic text Pancavimsa Brahmana, and it appears in other ancient texts such as the Shatapatha Brahmana as well, but not in the context of astrology.
Calendar and Hindu astrology
Budha is the root of the word 'Budhavara' or Wednesday in the Hindu calendar. The word "Wednesday" in the Greco-Roman and other Indo-European calendars is also dedicated to planet Mercury.Budha is part of the Navagraha in the Hindu zodiac system, considered benevolent, associated with an agile mind and memory. The role and importance of the Navagraha developed over time with various influences. Glorifying planetary bodies and their astrological significance occurred as early as the Vedic period and was recorded in the Vedas. The earliest work of astrology recorded in India is the Vedanga Jyotisha which began to be compiled in the 14th century BCE. The classical planets, including Mercury, were referenced in the Atharvaveda around 1000 BCE.
Nakshatras ruled by Budha are Ashlesha, Jyestha and Revathi.
The Navagraha was furthered by additional contributions from Western Asia, including Zoroastrian and Hellenistic influences. The Yavanajataka, or Science of the Yavanas, was written by the Indo-Greek named "Yavaneshvara" under the rule of the Western Kshatrapa king Rudrakarman I. The Yavanajataka written in 120 CE is often attributed to standardizing Indian astrology. The Navagraha would further develop and culminate in the Shaka era with the Shaka, or Scythian, people. Additionally the contributions by the Shaka people would be the basis of the Indian national calendar, which is also called the Shaka calendar.
Budha is also the root for name for the week day in many other Indian languages. In modern Hindi, Odia, Telugu, Bengali, Marathi, Urdu, Kannada and Gujarati, Wednesday is called Budhavara; Tamil: Budhan kizhamai; Malayalam: Budhanazhcha; Thai: Wan Phut.