In an unexpected discovery, astronomers utilizing NASA’s Hubble Space Telescope have found that a powerful jet emanating from a supermassive black hole at the center of a massive galaxy appears to trigger eruptions of stars along its path. These stars, referred to as novae, are not directly within the jet but instead exist in a perilous vicinity close by.
In an unexpected discovery, astronomers utilizing NASA’s Hubble Space Telescope have found that a powerful jet emanating from a supermassive black hole at the center of a massive galaxy appears to trigger eruptions of stars along its path. These stars, referred to as novae, are not directly within the jet but instead exist in a perilous vicinity close by.
This revelation has left researchers puzzled as they seek to comprehend its implications. “We’re not entirely sure what is happening, but it’s an incredibly thrilling finding,” remarked lead author Alec Lessing from Stanford University. “This indicates that we lack a complete understanding of how black hole jets interact with their environment.”
A nova occurs in a binary star system where an aging, swollen normal star releases hydrogen onto a white dwarf star that has already burned out. When the white dwarf accumulates enough hydrogen—up to a mile-deep layer—this layer detonates like a massive nuclear explosion. Although the white dwarf is not obliterated by the nova outburst, the explosion expels its outer layer and it resumes drawing fuel from its companion, restarting the nova-outburst cycle.
Hubble observed twice the number of novae erupting near the jet compared to other areas within the giant galaxy during the study period. The jet is generated by a central black hole that weighs 6.5 billion times that of our sun and is surrounded by a disk of swirling material. This black hole, which consumes incoming matter, ejects a jet of plasma that stretches over 3,000 light-years, traveling at nearly the speed of light. Anything caught within this energetic beam would be incinerated. However, the latest Hubble findings suggest that being in close proximity to this intense outflow also poses certain threats.
The observation of a greater number of novae near the jet indicates either a higher density of nova-producing binary star systems in the vicinity or that these systems are more likely to erupt compared to similar systems situated elsewhere in the galaxy.
“It seems there is something about the jet that affects the star systems that enter the surrounding area. Perhaps the jet somehow pushes hydrogen toward the white dwarfs, leading to more frequent eruptions,” explained Lessing. “However, it’s uncertain if this is a direct physical influence. It might instead be related to the pressure created by the light emitted from the jet. Accelerating the supply of hydrogen could result in faster eruptions. Something may be increasing the mass transfer rate to the white dwarfs near the jet.” Researchers also speculated that the jet might be heating the companion star of the dwarf, prompting it to overflow with more hydrogen. Yet, calculations indicated that the amount of heating is insufficient to cause such an effect.
“We are not the first to note that there seems to be more activity surrounding the M87 jet,” added co-investigator Michael Shara from the American Museum of Natural History in New York City. “However, Hubble has provided clear evidence of this increased activity, showcasing far more instances and statistical significance than we have had in the past.”
Shortly after Hubble’s launch in 1990, astronomers utilized its early Faint Object Camera (FOC) to investigate the center of M87, home to the immense black hole. They observed peculiar phenomena occurring around it, frequently spotting bluish “transient events” that could be signs of novae erupting like flashes of camera light. However, the FOC’s narrow field of view limited their ability to compare observations of the jet with areas nearby. For more than 20 years, the results remained intriguingly elusive.
Compelling evidence for the jet’s impact on the stars of its host galaxy was amassed over a nine-month period, during which Hubble used newer, wider-field cameras to tally the erupting novae. This endeavor posed a challenge for the telescope’s observing schedule, necessitating visits to M87 every five days for new images. Collectively, these observations yielded the most detailed images of M87 ever produced.
In total, Hubble identified 94 novae within the section of M87 captured by its camera. “We were not solely focused on the jet; we examined the entire inner galaxy. Once we overlaid all known novae on M87, it became clear—without the need for complex statistics—that there was a noticeable increase in novae along the jet. This discovery came simply from visually analyzing the images. While we were genuinely surprised, our statistical assessments of the data confirmed our observations,” Shara stated.
This achievement highlights Hubble’s unique abilities, as ground-based telescopes lack the resolution to detect novae deep within M87. Due to the intense brightness surrounding the black hole, these telescopes cannot resolve stars or their eruptions. Only Hubble is capable of identifying novae against the vivid backdrop of M87.
Novae are quite prevalent throughout the universe, with one nova occurring in M87 roughly every day. Considering there are at least 100 billion galaxies in the observable universe, an astonishing 1 million novae erupt somewhere in the cosmos every second.
