Black Hole Plasma Beam Increases Nova Explosions

by AMNH on Sep 26, 2024 10:00 am

Rendering of a beam of light to the left and a fiery ball emerging from a glowing spiral in outer space.

An artist's concept looking down into the core of the giant elliptical galaxy M87, left of center, with a supermassive black hole ejecting a 3,000-light-year-long jet of plasma. On the right is a binary star system with an erupting nova.
NASA, ESA, Joseph Olmsted (STScI)

Located about 54 million light-years away from Earth and home to 1 trillion stars, the massive elliptical galaxy M87 emits a blowtorch-like jet from a supermassive black hole at its core. This plasma blazes through space at nearly the speed of light, sizzling anything caught in its 3,000-light-year-long beam.

Now, research by astronomers using NASA’s Hubble Space Telescope has found that, if you’re a star, just getting close to this jet can be risky: stars seem to explode more frequently in the vicinity of the jet's trajectory.

A beam of light emerges from a glowing star against the dark of outer space.

A Hubble Space Telescope image of the giant galaxy M87 shows a 3,000-light-year-long jet of plasma blasting from the galaxy's central black hole. The jet seems to cause stars to erupt along its trajectory.
NASA, ESA, STScI, Alec Lessing (Stanford University), Mike Shara (AMNH)

These exploding stars, called novae, occur when a star like our Sun, called a red dwarf, spills hydrogen onto a dead white dwarf companion star. As the hydrogen accumulates on the surface of the white dwarf, it reaches a tipping point where it explodes like a hydrogen bomb. The white dwarf isn't destroyed by the nova eruption: it ejects its surface layer and then goes back to drawing fuel from its companion, starting the nova-outburst cycle over again.

Novae frequently explode throughout the M87 galaxy, but the new study finds there are twice as many novae near the jet as elsewhere in the giant galaxy.

“We’re not the first people who’ve said that it looks like there’s more activity going on around the M87 jet,” said Museum Curator Michael Shara, who was part of the team behind the findings, which will be published in Astrophysical Journal and are currently viewable on arXiv. "But Hubble has shown this enhanced activity with far more examples and statistical significance than we ever had before.”

Shortly after Hubble's launch in 1990, astronomers peered into the center of M87 and noted that unusual things were happening around the black hole, but the view was so narrow that Hubble astronomers couldn’t look away from the jet to compare with the near-jet region.

After the installation of wider-view cameras, astronomers counted novae near the jet over a nine-month interval from November 2016 to July 2017. The observations required revisiting M87 every five days, leading to the deepest images of the galaxy that have ever been taken.

This video plots the location of Hubble Space Telescope observations of novae – exploding stars – in the giant elliptical galaxy M87. The galaxy’s most notable feature is a 3,000-light-year-long jet of plasma ejected from a supermassive central black hole. Hubble observations identified numerous novae in the jet’s vicinity, identified by red circles that turn white when a nova explodes. NASA, ESA, Joseph DePasquale (STScI)

[An image of the giant elliptical galaxy Messier 87 (M87), which is bright white in the center with a long blue stream spilling out into the cosmos to its right. This is a 3,000-light-year-long jet of plasma ejected from a supermassive central black hole in the galaxy.

Text appears: “Hubble Space Telescope – Observations of the Jet in Messier 87. November 13, 2016 – July 31, 2017.”

A blue box appears around the stars and area of the image containing the jet of plasma and other surrounding stars in the area. The rest of the image fades and this box fills the screen.

Text appears: “Nova Outbursts Over 9 Months.”

Red circles appear on screen to indicate where novae – exploding stars – were detected from November 13, 2016 – July 31, 2017. This animation repeats seven more times.

The image fades back to the original image showing the full galaxy. Dotted lines appear dividing the galaxy into ten segments. Two segments – the one containing the plasma jet and the one directly opposite it, without any plasma – are highlighted.

Text appears: “In the same time frame”

The segment that does not contain the plasma jet is noted to have had 11 novae detected during this time period.

The segment that does contain the plasma jet is noted to have had 25 novae detected during this time period.]

The finding of twice as many novae near the jet implies that there are twice as many nova-forming double-star systems near the jet, or that these systems erupt twice as often as similar systems elsewhere in the galaxy.

The astronomers posited that something about the jet is either enhancing the fueling process and rate of explosions, or birthing new nova binaries in its vicinity. But neither hypothesis held up after calculations were made.

“We don’t know what's going on, but it’s just a very exciting finding,” said lead author Alec Lessing of Stanford University. “This means there’s something missing from our understanding of how black hole jets interact with their surroundings.”