Characters like planets in orbits around the sun; The Transit of Venus, by Shirley Hazzard. New York: Viking Press. $11.95.

Shirley Hazzard's "The Transit of Venus" is a novel of ancient concerns. Destiny figures as prominently here as in any Greek tragedy, and characters progress inexorably toward catastrophes of their own making. It is not "the gods" who have determined their fate but they themselves, and their lives, like literature, are but a long unwinding of plot.

As in classical and Shakespearean drama, the heavens, the landscape, even the weather mirror the novel's action, and the workings of the universe form its central metaphor. The title refers to the passage of the planet Venus across the face of the Sun, a rare but elusive occurrence that serves as an analogue for the spiritual journey of the heroine, Caroline (Caro) Bell.

Caro, "established as a child of Venus," is the desideratum of astronomer Ted Tice, who tracks her orbit through life but can never catch her in transit. Early in the novel Ted and another scientist tell the story of 18th-century astronomers who set sail from Europe to India and Tahiti to observe the transit but failed because of poor visibility and "distortions in the disc of Venus." Venus defies capture and explication. Venus, the unattainable.

It is clear that we are not dealing here with the garden-variety, revocate romance. Miss Hazzard's major characters are extreme -- in their demands on life and their conditions for love. Caro and here sister, Grace, orphaned at an early age in Australia (where Miss Hazzard was born) come to England where Grace , "fixed, terrestial, landlocked . . ." makes a conventional marriage to a conventional man.

Caro, on the other hand is a celestial creature, a person with a sense of destiny, who "has his notion of herself . . . of being different. Or better. She sees herself making large gestures." For Caro, love is no mere emotion or attraction but a moral issue.She develops a passion not for Ted but for the poet Paul Ivory, who possesses all the dazzling brilliance of a star. Paul, in contrast with Ted, is selfish, inconstant, deceitful, even criminal. Together they represent cosmic polarities, like the force of good and evil, order and chaos.

Caro is basically a passive person, like a planet in orbit around the sun, who tries to convince herself that character is as good as action. She is more at ease with Paul because he is weak, but she is attracted to men who are capable of a larger moral commitment. She marries Adam Vail, a champion of the politically oppressed, in part to acquire his virtue. Ted represents the ultimate exposure, the equivocation about herself she never was prepared to face , and just as it is her destiny to love him, it also is her destiny to try to elude him always, even at the cost of her life.

This is Miss Hazzard's fifth book. She has writtn four novels and a study of the United Nations, where she worked for several years, called "Defeat of an Ideal." Her experience at the UN obviously influenced the attitude toward political commitment, public vs. private morality, that pervades this novel.

"Transit of Venus" is an exceedingly ambitious novel, a stunning and at times bewildering galaxy of ideas. From a literary and intellectual standpoint it is a challenge, though at times the author's mental salutations are too quick to follow, the style too recondite to reward, the atmosphere too portentous for even a Gothic novel to bear. A more serious weakness is that the principal characters are personifications of ideas rather than real people, and one of the results is stilted dialogue such as the following:

Paul to Caro: "Have a bit of mercy."

Caro to Paul: "How should you hope for mercy, rendering none?"

Did lovers ever speak thusly?

In compensation, there are mordantly incisive, epigrammatic perceptions. Miss Hazzard can sum up a character in a single image, like an artist with a single stroke of the brush. For example: "There was some loneliness now to Una, an ignored or buried vitality: in her wealthy sparkle and disused allure she was like an abandoned mine."

Miss Hazzard's greatest achievement in this novel is the suspense she creates from unfinished relationships. Instead of spinning off in different directions through space, these characters collide once again, drawn together by an ineluctable magnetism. This happens rarely enough in life, and it is gratifying to find in a novel love that runs deep enough to shape destiny.