Astronomers have discovered a giant black hole at the center of Messier 84 “M84” (a massive elliptical galaxy). This giant black hole is leaving an “H”-shaped structure in the multimillion-degree gas around it. Using NASA’s Chandra X-ray Observatory, researchers mapped the hot gas in and around M84. This reveals the letter “H” formed by cavities in the hot gas around the black hole created by jets of particles blasted away from the black hole. The study also shows that the jets may affect the flow of hot gas toward the black hole, slowing the rate at which gas falls onto it. The results were reported in the Royal Astronomical Society Monthly Notices.

With what appears to be a single letter etched into the X-ray glow surrounding it, a massive black hole at the center of an elliptical galaxy is leaving its imprint on its surroundings.

The H-shaped Structure in M84’s Gas Cavity:

A comprehensive new X-ray map of the multimillion-degree gas surrounding the galaxy Messier 84 (M84) reveals this “H”-shaped structure. As gas is captured by the black hole’s gravitational force, a portion of it will descend into the abyss, never to be seen again. Some of the gas, however, escapes this fate by being expelled from the black hole in the form of particle streams. These projectiles can eject holes from the hot gas surrounding the black hole. 

Given the orientation of the jets toward Earth and the profile of the heated gas, it appears that the cavities in Messier 84 resemble the letter “H.” The H-shaped structure in the gas is an illustration of pareidolia, which occurs when individuals perceive familiar shapes or patterns in random data. Pareidolia can occur in all types of data, including images of clouds, mountains, and astronomical objects.

messier 84
Credits: X-ray: NASA/CXC/Princeton Univ/C. Bambic et al.; Optical: SDSS; Radio: NSF/NRAO/VLA/ESO; Image processing: NASA/CXC/SAO/N.Wolk

What is the significance of the NASA Chandra X-ray Observatory?

Using NASA’s Chandra X-ray Observatory, astronomers created a map of the hot plasma (pink) in and around Messier 84, reaching within 100 light-years of the central black hole of the galaxy. This gas radiates at temperatures in the tens of millions of degrees, allowing X-rays to be its primary mode of observation. The enormous letter “H” is approximately 40,000 light-years tall, or roughly half of the Milky Way’s girth. 

The radio image from the Karl G. Jansky Very Large Array (VLA) of the National Science Foundation (blue) reveals the plumes emanating from the black hole. Sloan Digital Sky Survey optical data (white) depicts M84 and neighboring galaxies. The letter H and the black hole’s location are labeled. A further image depicts a zoomed-in view of the region marked with a square, as well as distinct labels for the galaxy and jets in the optical and radio images, respectively.

Do jets have a greater influence on the flow of matter towards a black hole than the black hole’s gravitational pull in Messier 84?

Jets may influence the flow of hot gas toward the black hole even more than the black hole’s gravitational pull, according to researchers investigating M84 with Chandra and the VLA. For instance, the team estimates that matter falls towards the black hole from the north — along the direction of the jet seen in radio waves — at a rate of approximately 500 times the mass of the Earth per year, compared to a rate that is only a quarter of that from directions where the jet is not pointing, such as the east and west. The cavities may lift gas in the direction of the jet, slowing the rate at which gas descends onto the black hole.

The Bondi accretion mode:

The authors tested the Bondi accretion model, in which all matter within a certain distance from a black hole — effectively within a sphere — is near enough to be affected by a black hole’s gravity and begin falling inwards at the same rate from all directions. (The dashed circle in the close-up image is centered on the black hole and indicates the approximate distance at which gas should begin to descend inwards.) 

This effect is named after the astronomer Hermann Bondi, and “accretion” refers to matter plummeting into a black hole. The new results indicate that Bondi accretion is not occurring in Messier 84 because the matter is not descending uniformly from all directions into the black hole.

How does the black hole in Messier 84 compare to the one in M87?

Both Messier 84 and Messier 87 are located in the Virgo Cluster and contain supermassive black holes. The black hole in M87 was the first one captured by the Event Horizon Telescope network, while the black hole in M84 is one of the few black holes close enough to Earth for astronomers to study in detail. 

While both black holes produce a discharge of particles, the point source of X-rays from material closer to the black hole is over ten times fainter in M84 than in M87. This allows astronomers to analyze gas falling towards the black hole in Messier 84 that is further away, as the faint X-rays produced by this gas are not overwhelmed by the X-ray glare from the point source.

The publication of the analysis:

The Monthly Notices of the Royal Astronomical Society will publish a paper describing these results, and a preprint is available here. Christopher Bambic, a graduate student at Princeton University, directed the research along with other authors.