Karthigai is considered as the birthday of Lord Muruga and those who observe Karthigai vrata on this day reap many good things in life. In temples, Special Abishegam is performed to Lord Muruga on the Karthigai day every month.
Karthigai is a star among 27 stars and falls on the day when the Moon crosses the Karthigai constellation of six stars once in a month as per lunar calendar.
These six stars are the six Karthigai nymphs who took care of Lord Muruga after he was born out of the third eye of Lord Shiva. They are bestowed immortality by Lord Shiva for the service rendered by them and thus they shine in the sky as a constellation in the name of Karthigai.
Let us worship Lord Muruga on the day when Karthigai falls and let us obtain His grace and blessings.