Ardra nakshatra is the sixth of the 27 birth stars or nakshatras in Hindu astrology and it lies in the lunar zodiac belt. It is also called Arudra and Thiruvathirai. As per Ardra nakshatra story found in the Skanda Purana, once Shiva cut off of the fifth head of Brahma for causing suffering on earth through his creations. The fifth head became a star known as Mrigasira or Mrigasheersham or Makayiram. It is said that Shiva became so enchanted by the beauty of Mrigasira that he himself took the shape of a star, Ardra, and came close to Mrigasira. In the zodiac, the constellation containing Ardra is near Mrigasira, and is in the shape of a hunter.
Ardra is place in Gemini, all its four quadrants occupying this
sign. The presiding deity of the star is Rudra and its ruler is Rahu.
Ardra is called a daruna nakshatra (misery-causing star).
Hence in the opinion of astrologers, this star is not good for auspicious functions.
However, it is supposed to be favorable for undertaking work connected with
fire and with machinery. As Ardra is associated with Shiva, the star is considered
to be auspicious for establishing and consecrating Shiva temples.
A person born in Ardra birth star is supposed to be boatsful
and proud, crafty in speech, uncharitable in actions and ungrateful.
Ardra nakshatra is dear to Shiva and He is worshipped on Thiruvathirai
or Arudra nakshatra in Tamil Margazhi month and during the same period in
Malayalam Dhanu Masam. The cosmic dance of Shiva is believed to have taken
place on Arudra nakshatra.
Both Adi Shankaracharya (exponent of Advaita philosophy) and
Ramanuja (an exponent of Visishtadvaita philosophy) were born under Arudra or Thiruvathira.