Star of the sea
The "quiet church" from which the sound of prayer "streamed forth at times" is obliquely named at the end of the sentence, when we learn that the prayers are addressed to "Mary, star of the sea." Mary, Star of the Sea is a Roman Catholic church in Sandymount that at the time of the novel was located very close to the shore.
Stella Maris is one of many titles of the Blessed Virgin Mary. Gifford notes (376) that as Queen of Heaven she is crowned with twelve stars, according to Revelation 12:1. The association with the sea is as ancient as St. Jerome, holding both metaphorical significance (Mary is "a beacon ever to the stormtossed heart of man," offering deliverance from the waves of passion and temptation) and literal (Mary, in this guise, represents hope to seafarers). Polaris, the ancient reference mark for sailors, has sometimes been called the sea-star.
Prayers are being addressed to the Virgin late on a Thursday evening because a temperance retreat is being conducted in the church. Joyce had represented such a retreat once before, in "Grace," the next to last story of Dubliners. That retreat took place in "the Jesuit Church in Gardiner Street," in the north part of central Dublin. But the Sandymount church holds significance for Mr. Kernan, the alcoholic whose Catholic friends maneuver him into attending a temperance retreat, and especially for his wife: "In her days of courtship Mr Kernan had seemed to her a not ungallant figure: and she still hurried to the chapel door whenever a wedding was reported and, seeing the bridal pair, recalled with vivid pleasure how she had passed out of the Star of the Sea Church in Sandymount, leaning on the arm of a jovial well-fed man who was dressed smartly in a frockcoat and lavender trousers and carried a silk hat gracefully balanced upon his other arm. After three weeks she had found a wife's life irksome and, later on, when she was beginning to find it unbearable, she had become a mother."
Mrs. Kernan's association of the Star of the Sea with a happier time of life, before eager anticipations of marriage were supplanted by the brutal reality of living with an alcoholic, no doubt has bearing on the associations established in Nausicaa. This is the parish church of Paddy Dignam, whose home is likewise very close to the shore, and whose alcoholism has just shepherded him to an early grave and left his family confronting poverty. Gerty MacDowell, who sits on the shore listening to the ceremony in the church, has grown up in a home where her father's alcoholism sometimes led to domestic violence. She passes her days dreaming of marriage to a prince charming, but she is also well aware of men's capacity for brutality, and by modeling herself so obsessively on the Blessed Virgin she seems in part to be aspiring to a condition of perpetual chastity.