Products You May Like
Artist’s illustration of a star next to its stellar companion, which has become a nova.
Credit: NASA’s Goddard Space Flight Center
Although they represent different stages in a star’s life, novae and black holes are considered separate astronomical phenomena. One is a nuclear explosion that occurs when enough hydrogen accumulates on the surface of a white dwarf star; the other is the infinite (and existential dread-inducing) remnant of a star that has gone supernova. And while the two phenomena often exist within fairly close proximity of each other—say, within the same galactic neighborhood—one doesn’t usually cause the other to come to fruition.
That’s what scientists once believed, at least. Thanks to recent findings made via the Hubble Space Telescope, plasma jets spewing from hungry black holes can ignite nova explosions, resulting in the demise of nearby stars. These findings were published late last week in an open-access paper for The Astrophysical Journal.
Via two Hubble imaging surveys, researchers at Columbia University, Stanford University, and NASA have observed that the supermassive black hole at the center of Messier 87 (M87) is surrounded by a wealth of novae. The team observed 135 classical novae—those that are triggered by a thermonuclear explosion on the surface of a white dwarf within a two-star system—in M87, nearly tripling the number of novae originally expected to exist within that galaxy. Naturally, this led the team to wonder why novae were so abundant in that particular galaxy.
Novae (represented in pink and cyan) around M87’s center.
Credit: Lessing et al, The Astrophysical Journal/DOI 10.3847/1538-4357/ad70b7
When a black hole gobbles down vast amounts of energy and matter, it can produce jets of plasma that spew across space at nearly the speed of light, earning the sprays the nickname “relativistic jets.” Not only do these jets contain plasma (which itself consists of electrons and protons), but they also hurl radiation in the form of radio waves, visible light, and X-rays. Theoretically, this abrasive activity could strip away some of the outer layers of a star from a two-star system, allowing the star’s companion to accrete what’s been removed. Because accretion is what kicks off a nova, there’s a chance that a black hole’s plasma streams could indirectly trigger a stellar explosion.
The researchers saw that M87’s classical novae were “strongly concentrated along that galaxy’s jet,” lending a touch of possibility to the above theory. After all, simulations show that the likelihood of such a concentrated nova cluster occurring by chance around M87’s supermassive black hole is only around 0.3%. Surely some other force was at play, right?
The team still isn’t sure. “The novae near the jet display outburst characteristics (peak luminosities, colors, and decline rates) that are indistinguishable from novae far from the jet,” they write. “An alternate explanation is the presence of a genuine surplus of nova binary systems near the jet, perhaps due to jet-induced star formation.” Either way, it appears M87’s supermassive black hole might be behind the unusually high number of neighboring novae—the exact mechanism of its work is just unclear.