Nakṣatra — The Lunar Mansions and the Calendar of Devotion
Nakṣatra ('that which does not decay'; na = not + kṣatra from kṣar = to decay, to perish; alternatively, from nakta = night + atra = here, 'that which is present at night') refers to any one of the 27 (or 28, when the 28th Abhijit is counted) star-groups — lunar mansions — that divide the zodiacal belt of approximately 360 degrees into equal segments of approximately 13 degrees 20 minutes each, through which the moon passes in its monthly cycle of approximately 27.3 days.
The 27 nakṣatras in the traditional order, each governed by a presiding deity (nakṣatra-devatā), are: Aśvinī, Bharaṇī, Kṛttikā, Rohiṇī, Mṛgaśirā, Ārdrā, Punarvasu, Puṣya, Āśleṣā, Maghā, Pūrva Phalgunī, Uttara Phalgunī, Hasta, Citrā, Svātī, Viśākhā, Anurādhā, Jyeṣṭhā, Mūla, Pūrvāṣāḍhā, Uttarāṣāḍhā, Śravaṇa, Dhaniṣṭhā, Śatabhiṣā, Pūrva Bhādrapadā, Uttara Bhādrapadā, and Revatī.
For Śrī Vaiṣṇava practice, the theological and liturgical importance of nakṣatras is primary in several domains:
1. Thirunakshatram — the birth stars of the Āzhvārs and Āchāryas: Every Āzhvār and every Āchārya in the Śrī Vaiṣṇava paramparā is associated with a specific nakṣatra and Tamil month as their birth anniversary — the Thirunakshatram. These days are among the most important festival occasions in the Śrī Vaiṣṇava calendar. The Thirunakshatrams are observed with special kālakṣepam (theological discourses), prabandham recitation, tirtha distribution, and prasādam at temples and in homes. For example: Nammāzhvār's Thirunakshatram falls in the Vṛścika (Kārttika) month on Viśākhā nakṣatra; Rāmānuja's Thirunakshatram is in Citrā nakṣatra in the Panguni month.
2. Pañcāṅgam and daily auspiciousness: The daily Pañcāṅgam (five-limbed almanac) lists the reigning nakṣatra of each day alongside tithi, yoga, karaṇa, and vāra. The nakṣatra at any given moment determines the auspiciousness or inauspiciousness of an activity: certain nakṣatras are favorable for vivāha (marriage), others for upanayana, travel, sowing, building. The nakṣatra of a person's birth — their jāti nakṣatra or janma nakṣatra — is one of the most personal and significant factors in Vedic astrological calculation (jāta-karma).
3. Pañca-saṃskāra: The timing of pañca-saṃskāra — the five-fold Śrī Vaiṣṇava initiation rite of samāśrayana — is typically determined with reference to the nakṣatra, ensuring the maṅgala (auspicious) alignment of the planets and the moon's mansion at the time of the transformative ceremony.
The nakṣatra system is among the oldest astronomical knowledge preserved in the Vedic tradition, predating the solar zodiacal system of classical Greco-Roman astrology. The Vedāṅga Jyotiṣa (c. 1400–1200 BCE) is almost entirely structured around nakṣatra-based calendar keeping — a testament to the antiquity and centrality of the lunar mansion system in the Vedic worldview.