Stars, much like living beings, go through a life and death cycle, with the most massive stars ending their lives in spectacular explosions called supernovae. These explosions often leave behind mysterious remnants: either black holes or neutron stars that shine brighter than their host galaxies for months. However, astronomers have recently observed a groundbreaking exception— a massive star that collapsed directly into a black hole without any explosion.
The Usual Fate of Massive Stars: Supernovae Explosions and Beyond
Typically, the life of a massive star is balanced by the outward push of nuclear fusion and the inward pull of its own gravity. When the hydrogen fueling the fusion runs out, this delicate balance breaks, and the star collapses, resulting in a supernova explosion. This explosive finale often leaves behind either a black hole or a neutron star. However, researchers now suggest that some stars may bypass this explosion entirely, collapsing quietly into black holes.
A Silent Collapse in the Andromeda Galaxy
In a recent study titled “The Disappearance of a Massive Star Marking the Birth of a Black Hole in M31,” scientists documented a massive hydrogen-depleted supergiant in the Andromeda Galaxy (M31) that became a black hole without a supernova. Led by Kishalay De, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research, the study reveals an exceptional event in the star lifecycle.
A Rare Event: Core-Collapse Supernovae and the Mystery of M31-2014-DS1
This unusual phenomenon is known as a core-collapse supernova, a rare event that only occurs in our Milky Way about once every hundred years. First spotted in 2014, the star, named M31-2014-DS1, initially displayed an intense brightness in the mid-infrared (MIR) range, which persisted for over 1,000 days. It then faded dramatically between 2016 and 2019 and became invisible in recent observations.
What Makes M31-2014-DS1 Unique?
According to the researchers, this star started with 20 times the mass of the Sun and was in its terminal nuclear-burning phase with 6.7 stellar masses. Although a dust shell typically left behind by supernovae was observed around it, there was no optical explosion to signal the usual supernova process.
“The dramatic and sustained fading of M31-2014-DS1 is exceptional in the landscape of variability in massive, evolved stars,” the research team noted, pointing to a sudden end in nuclear burning and a shock that couldn’t overcome the collapsing material.
Failed Supernovae: A Rare Class of Star Deaths
Interestingly, failed supernovae are incredibly rare. In 2009, astronomers confirmed the first known instance in the NGC 6946 “Fireworks Galaxy,” where a supergiant red star collapsed directly into a black hole without a supernova.
The Unanswered Mysteries of Supernovae and Black Holes
This latest discovery highlights how much there is to learn about supernovae and stellar death. As astronomers continue to investigate stars like M31-2014-DS1, they hope to answer some of the most profound questions about star formation, black holes, and the life cycles of massive stars.
