WHEN WORLDS COLLIDE?

It should be the happiest day of her life.

As “Melancholia” opens, Justine (Kirsten Dunst) has just married her true love, the handsome, caring Michael (Alexander Skarsgård). Now the two are the guests of honor at a lavish wedding reception funded by Justine’s frazzled sister, Claire (Charlotte Gainsbourg), and her self-important husband, John (Kiefer Sutherland).

Justine’s friends and family — including her divorced parents (John Hurt and Charlotte Rampling)—have gathered to celebrate the nuptials. Meanwhile, her overbearing boss (Stellan Skarsgård) has just promoted her to art director of his advertising firm.

Justine should be happy. She should be ecstatic. Instead, her brave smiles conceal the scars of a deep and damaging depression.

Her sense of unease may be connected to the recent discovery of Melancholia, the mysterious planet that until now lay hidden behind the sun. Now the planet is moving toward Earth on a possible collision course, its blue bulk an ominous specter in the summer sky.

Yet while the rapid approach of Melancholia fills Claire with mounting dread, Justine experiences a growing calm.

“All I know is life on Earth is evil,” she tells her sister matter-of-factly. “I know things.”

A mournful meditation on beauty and death, “Melancholia” ranks among Lars von Trier’s most lovely achievements on screen. It’s a sumptuous film—part science fiction fable, part psychodrama — that contrasts striking special effects with far humbler human emotions.

The movie’s greatest strength lies in Manuel Alberto Claro’s peerless cinematography.

“Melancholia’s” slow-motion introduction reveals an alien landscape: power poles ringed with St. Elmo’s fire, manicured shrubs casting sinister shadows across the lawn. That unearthly sensation is echoed later in the film, when we spy Kirsten Dunst lying naked, sylph-like, under the eerie blue glow of Melancholia.

Best known from the “Spider-Man” movies, Dunst delivers a surprisingly nuanced performance here as an emotional wreck of a woman. Her interactions with the equally strong Charlotte Gainsbourg exhibit a sisterly bond strained by years of disappointment and betrayal.

There are sparks of quirky humor in “Melancholia,” thanks mostly to John Hurt as Justine’s philandering father and Udo Kier as a pompous wedding planner. But most of the film proceeds at a somber, stately pace.

Seen as a whole, “Melancholia” is atmospheric, operatic and occasionally overwhelming — a set of pretty postcards from the end of the world.