Ashwini is the first of the twenty-seven nakshatras, the lunar mansions of Vedic astronomy, and occupies the opening 0 to 13 degrees 20 minutes of the sidereal zodiac in Aries. Each nakshatra is a segment the Moon crosses in roughly a day, and the scheme is older than the twelve-sign zodiac in Indian usage. Its ruling planet in the Vimshottari cycle is Ketu, the Moon's descending node; its presiding deities are the Ashwini Kumaras, the twin horsemen and physicians of the gods; and its symbol is a horse's head. In jyotisha the mansion is read as Deva gana, classed among the divine-tempered stars, and is associated with swiftness, healing, and fresh beginnings, the qualities the twin horse-riders carry. These attributions are traditional readings within the astrological system rather than statements about the stars themselves; the underlying asterism lies near the head of Aries.
The relationship between this system and its two sibling lunar-zodiacs is worth stating plainly, because it is a genuinely open scholarly question. The twenty-seven Indian nakshatras, the twenty-eight Chinese xiu, and the twenty-eight Arabic manazil al-qamar all divide the ecliptic by the Moon's own motion, and Babylonian astronomy is often proposed as a common ancestor behind all three, though the transmission history between them has never been conclusively resolved; orientalist scholars have argued for transmission running in more than one direction and for independent development, without reaching agreement. Part of the difficulty is the count itself: the Moon's sidereal period is about 27.3 days, so 27 and 28 are both reasonable roundings, and an older 28-nakshatra list, with an extra mansion called Abhijit, is attested before the 27-fold count became standard.