This photo is from the official trailer of "Supernova," distributed by StudioCanal.

“Supernova” opens in total darkness. Slowly, stars emerge. One shines brightly, then disappears.

Tusker, Stanley Tucci’s character (“Spotlight”), later explains that everything is made from dying stars, which turn into supernovas that spew “star stuff,” the building blocks for life, through space. With a gigantic flash, these interstellar explosions create the universe as we know it.

There is a vitality to destruction. A beauty, even. 

That’s why “Supernova” is a beautiful film. Its subject matter, Tusker’s worsening dementia and its effects on his partner Sam (Colin Firth, “The King’s Speech”) are upsetting, even gruesome at times.

The relationship between Tusker and Sam, who are first shown nude and in bed together, is unflinchingly real. Their love’s complete believability makes the film heartbreaking when dementia escalates its attack.

The couple has decided to take one last vacation through the English countryside, staying in an RV with their dog Ruby. They drive through locations important to their relationship, like a quiet lake where they spent their first night together, under the stars. Speaking of stars, the illness works like a supernova in reverse, flashing through lives that have already been lived, eating them away and leaving emptiness in its wake. Maybe it’s more of a black hole.

The film is a day-to-day portrait of Tusker and Sam’s relationship, showing both what makes the men perfect for one another — nights spent stargazing and days bickering like an old married couple, as their van sails through verdant English hills — and the horror of the imminent illness, the far-off look in Tusker’s eyes as the fog of memory continues its inevitable descent. 

Tucci exhibits a deep sadness in every scene, sometimes understated, sometimes blazingly tragic, that shows the viewer the heartbreaking reality of losing oneself as the days go by. Firth will also leave most viewers reaching for the tissue box. Sam is mourning his lover while the man is still alive, simultaneously bottling the terrible despair so he doesn’t make Tusker feel even worse.

“Supernova” is patient, portraying the gradual tragedy that accumulates because of this dreadful disease. The film’s slow pace doesn’t make its conclusion less tragic, though, only more brutally real.

What makes the film unique is that, while the couple depicted are in a gay relationship, there is no discussion of persecution or even gay identity in general. “Supernova” could be about any couple. This itself is sort of radical. Most gay-centered dramas focus on prejudice, a “coming out” story or some combination of the two. The question, though, is this: Should homosexuality be performed by heterosexual actors? 

Speaking from my subjective gay experience, I think the era where this is unquestionably fine has passed. Ten years ago, when most producers wouldn’t touch a mass-market gay-themed movie like “Love, Simon,” I would have said that queer representation was so necessary that, if it took heterosexual actors to get the story told, then fine.

Yet, in 2021, queer representation has become mainstream. Stories as diverse as “Ammonite” to Pixar’s “Onward” are including LGBTQ+ characters and telling all sorts of stories. This flourishing in the topic hasn’t come with a proportionate rise in LGBTQ+ performers, however. The queer leading characters in “Ammonite,” for example, were played by heterosexual actresses. Maybe this just takes time.

Still, gay identity isn’t a costume that can be slipped on. Even if Supreme Court Justice Amy Coney Barret says so, it’s not a “preference.” It’s an identity, a community.

It is vital to include LGBTQ+ voices behind and in front of the camera, especially when the films themselves are about LGBTQ+ characters. While Firth and Tucci are great, there are also plenty of gay actors, like Ian McKellen (“The Hobbit: an Unexpected Journey”) and B.D. Wong (“Nora From Queens”), who have lived as gay men in the 20th century, experiencing traumas like Section 28 and the AIDS crisis, and have grown old and loved and lost. This was their story to tell.

Daily Arts Writer Andrew Warrick can be reached at warricka@umich.edu