Betelgeuse, a colossal tangerine-red star, is barreling toward annihilation. The stellar body is pronounced “Beetlejuice,” like the guy in the afterlife whose name you’re not supposed to say thrice. And at some point soon, in galactic terms, it is expected to explode as a supernova, setting the night sky ablaze.

Despite its self-destructive proclivities, the irritable giant has managed to make, and keep, a friend.

On Monday, a team of astronomers announced that they had spotted another star hewing extremely close to Betelgeuse. So close, in fact, that the second star plows through the tenuous outer atmosphere of the red supergiant.

The two objects make for a strange pair. Unlike Betelgeuse, which is approaching the end of its life, the blue-white companion (or Betelbuddy) has yet to start burning hydrogen in its core. In other words, the star hasn’t entered the chapter of its life known as the main sequence — one that characterizes many stars, including our own.

“You have a star that is about to die, and it’s being orbited by a star that’s not fully born,” said Miguel Montargès, an astronomer at the Paris Observatory who was not involved with the new research.

“Isn’t that crazy?” said Steve B. Howell, a scientist at NASA Ames Research Center in California and one of the discoverers of the companion star. “It’s kind of crazy.”

It may seem cute that Betelgeuse has a friend. But with friends like Betelgeuse, who needs enemies? If Betelgeuse goes supernova soon, the Betelbuddy will probably be obliterated. Even if the supernova isn’t imminent, it looks as if the companion star “will actually spiral into Betelgeuse and be engulfed,” Dr. Howell said. In other words, in either scenario, “it’ll be destroyed,” he said.

Jared Goldberg, an astrophysicist at the Flatiron Institute in New York who was not involved with the new research, puts it more delicately. “Betelgeuse and its buddy will hug eternally,” he said.

Found 700 light-years away in the shoulder of the constellation Orion and visible with the naked eye, Betelgeuse has bewitched skygazers throughout human astronomy. The star is 10 million years old, making it a whippersnapper in astronomical terms. But it’s also elephantine: 15 times more massive than the sun, 700 times the size and sometimes 14,000 times as bright.

Massive stars “live fast, burn bright and die young,” said Rebecca Oppenheimer, an astrophysicist at the American Museum of Natural History in New York who was not involved with the new research. That means Betelgeuse is in its twilight years, and an explosion is incoming.

“It could be tomorrow, or it could be in many generations,” Dr. Goldberg said.

In the interim, Betelgeuse has been offering puzzles for astronomers. Its brightness dimmed so drastically in 2019 that scientists wondered if it were about to go supernova. The explanation turned out to be stellar indigestion: The star burped a large cloud of gas, which formed a light-blocking haze.

Betelgeuse also has an unexplained five-to-six-year cycle of brightening and dimming. Recently, some (including Dr. Goldberg) predicted that a companion star may be responsible, interacting with Betelgeuse to periodically change its brightness. But attempts to find that companion with various space observatories came up empty.

The remarkable resolution of the Gemini North telescope atop Mauna Kea volcano in Hawaii provided the breakthrough. Dr. Howell’s team used the telescope to find Betelbuddy, which Betelgeuse’s blinding inferno had concealed.

“It’s incredible that they found it,” Dr. Montargès said.

The discovery means that Betelgeuse is a binary star system. And the mystery of the star’s periodic spikes in brightness now has an answer.

The companion orbits Betelgeuse once every five to six years, sweeping through the red supergiant’s outer atmosphere. Betelgeuse’s companion is also extremely hot. In moving through all that gas, Betelbuddy heats and ionizes some of it, causing it to glow bright enough to be seen 700 light-years away.

Sadly for the little firestarter, it is expected to be gobbled up by the red supergiant within about 10,000 years.

“It’s starting to become a real star,” Dr. Howell said of the Betelbuddy, “but unfortunately it’ll never make it.”