A beard is a common symbol of age, wisdom and authority across many cultures, from Greek philosophers to ancient Mesopotamian kings. A "beard of stars" could metaphorically describe an ancient, all-knowing cosmic entity.
In Thomas Gray's "The Bard" (1757) a similar celestial majesty is evoked by the lines
Sublime their starry fronts they rear;
And gorgeous dames, and statesmen old
In bearded majesty, appear.