Astronomers Observe Extremely Rare ‘Failed Supernova’ In Andromeda Galaxy

A massive star in the Andromeda Galaxy has vanished. Over nearly a decade, astronomers watched as the brilliant supergiant faded from view until it became completely invisible. The star didn’t explode in a supernova as expected. Instead, it simply disappeared, collapsing into a black hole in what scientists call a “failed supernova.”

The star, designated M31-2014-DS1, once burned about 100,000 times brighter than our sun. Between 2016 and 2019, it faded dramatically in visible light. By 2023, when astronomers checked again, the star had essentially vanished.

Watching A Star Disappear In Real Time

Kishalay De from Columbia University led the team that tracked this stellar disappearance using data from the Hubble Space Telescope and NASA’s infrared space survey. What they documented in the journal Science represents something rarely observed: a massive star collapsing into a black hole without the usual fireworks.

Typically, when massive stars reach the end of their lives, their cores collapse and send shockwaves through the star’s outer layers. Those shockwaves blow the star apart in a brilliant supernova explosion visible across vast cosmic distances. But sometimes those shocks aren’t strong enough. The outer layers fall back onto the collapsing core instead of flying outward, and the star simply winks out of existence.

M31-2014-DS1 showed exactly this behavior. The research team dug through archival observations dating back to 2005 and found the star had been acting strange for years. It was surrounded by a thick cloud of dust from shedding enormous amounts of material, a sign something was going very wrong inside.

In 2014, the star started brightening in infrared light, the kind our eyes can’t see but specialized telescopes can detect. The infrared glow peaked and then faded over the next few years as the star continued its slow disappearance. The team interprets this as hot dust forming from material puffed out during the early stages of collapse.

Why This Star Took So Long To Vanish

The long, slow fade is what makes this event special. If the star were simply falling in on itself under gravity alone, it would have disappeared within about seven months. Instead, it took more than three years to fade away. That extended timeline tells astronomers that energy released during the core collapse was holding up the outer layers temporarily, delaying their inevitable fall inward.

The team’s calculations suggest the star started its life weighing about 13 times as much as our sun but had shed most of that mass over millions of years. By the time it collapsed, only about 5 solar masses remained. When the core gave way, it released tremendous energy, but not nearly enough to blow the star apart like a normal supernova.

The weak shock managed to blow off only a small amount of material (about one-tenth the mass of our sun) at modest speeds. That ejected gas cooled and formed dust grains, creating the infrared glow astronomers detected. Meanwhile, the vast majority of the star’s mass fell back onto itself, creating a black hole.

For the next few years, leftover material continued falling into the newly formed black hole. Initially, so much material was falling in that the black hole couldn’t swallow it all efficiently. During this phase, the system stayed relatively bright. But as the infall rate dropped, the brightness faded in lockstep until almost nothing remained visible.

What’s Left Behind

When Hubble looked at the location in 2022, it detected no visible light at all. In infrared wavelengths, though, astronomers spotted a faint remnant: a dusty ember more than 10,000 times dimmer than the original star. Follow-up observations in 2023 from ground-based telescopes in Hawaii confirmed this faint glow. It’s the leftover dust shell surrounding what little remains visible of the system.

This isn’t the first time astronomers have caught a star vanishing. Another case from 2015, in a galaxy called NGC 6946, showed remarkably similar behavior: a bright outburst, followed by a dusty envelope, then fading to a fraction of its original brightness over several years. Analyzing both events together reveals a pattern of how certain massive stars meet their end not with a bang, but with a whimper.

The Failed Supernova

What determines whether a massive star explodes or quietly collapses may come down to how much weight it loses before the end. M31-2014-DS1 had shed most of its outer hydrogen envelope through powerful stellar winds or by transferring material to a companion star. The earlier case NGC 6946-BH1 retained more of its hydrogen layers. Despite these differences, both underwent failed supernovae, suggesting multiple pathways can lead to this quiet collapse. The thickness of the remaining hydrogen envelope appears to affect the duration of the process; NGC 6946-BH1’s thicker envelope produced a longer initial outburst before fading.

No X-rays have been detected from either vanishing star, which might seem odd since material falling into a black hole typically produces high-energy radiation. But the same dusty gas creating the infrared glow also blocks X-rays from escaping, hiding the black hole’s presence from certain types of telescopes.

The odds of finding even one of these events were low, somewhere between 1 and 20 percent, based on previous estimates of how often massive stars fail to explode. Finding two suggests astronomers might discover more as surveys improve. Or it could mean the relationship between a star’s birth mass and its final fate is more complicated than simple cutoffs.

For stars born weighing more than about 12 times the sun’s mass, the difference between explosion and disappearance may hinge on subtle factors during their evolution that remain difficult to predict. Some become supernovae. Others, like M31-2014-DS1, simply fade away.

The decade-long observations required to track M31-2014-DS1 from its first signs of trouble through its final disappearance show why these vanishing stars have been so hard to find. Catching one requires watching millions of individual stars for years, hoping to be looking at the right one at the right moment. As astronomical surveys get better at this kind of long-term monitoring, astronomers expect to find more stars that defy the explosive death we’ve come to expect from giants like these.