Astronomers discover how energy escapes from galaxy center

Unlike the most energetic galaxies, our Galaxy is inactive.

galaxy gaia

Aerial view of our Milky Way and neighboring galaxies from Gaia. Maps show the total brightness and color of the stars (top), the total density of stars (middle), and the interstellar dust filling the galaxy (bottom). Note how, on average, there are about ~10 million stars per square degree, but some regions, such as the Galactic Plain or the Galactic Center, have stellar density well above the overall average.

Credit: ESA/Gaia/DPAC

Although we have a supermassive black hole, it is not actively active.


This 20-year time-lapse of stars near the center of our galaxy comes from ESO published in 2018. Notice how the resolution and sensitivity of the features gets sharper and better towards the end, orbiting the (invisible) central supermassive black of our galaxy. hole. Practically every large galaxy, even early on, is known to be home to a supermassive black hole, but only the one at the center of the galaxy is large enough to see the motion of individual stars around it. Is, and thus can accurately determine the black hole. Mass of the hole. The actual number density of black holes in the universe, and their number density as a function of mass, are only poorly estimated, with large uncertainties remaining.

Credit: ESO/MPE

Actively feeding supermassive black holes represent the most energetic engines in the universe.

Centaurus A X-ray

The galaxy Centaurus A is the closest example of an active galaxy to Earth, with its high-energy jets caused by electromagnetic acceleration around the central black hole. The extent of its jets is much smaller than those observed by Chandra around Pictor A, which are themselves much smaller than the jets of Alysionus, which are even smaller than those found in giant galaxy clusters. This image, alone, shows high temperatures ranging from ~10 K to several million K and relativistic jets that are physically larger than even the stellar extent of the galaxy.

Credits: X-ray: NASA/CXC/CFA/R.Craft et al Radio: NSF/VLA/Univ. Hertfordshire/M.Hardcastle et al. Optical: ESO/VLT/ISAC/M.Rezkuba et al.

Except for the Big Bang, no other astronomical event can dominate active galactic nuclei (AGN) and quasars.

Ophiuchus X-ray largest eruption cavity

Evidence of the largest explosion ever observed in the universe comes from combining X-ray data from Chandra and XMM-Newton. The explosion is generated by a black hole located in the cluster's central galaxy, which has spewed jets and created a large cavity in the surrounding hot gas. Researchers estimate that this explosion released five times more energy than the previous record holder and hundreds of thousands of times more energy than a typical galaxy cluster. Gas emitting X-rays can reach temperatures ranging from millions to ~100 million K.

Credits: X-Ray: Chandra: NASA/CXC/NRL/S. Giacintucci, et al., XMM-Newton: ESA/XMM-Newton; Radio: NCRA/TIFR/GMRT; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF

From X-rays through radio waves, AGN and quasar engines shine brightly.

To the left and right of a central, giant elliptical galaxy, several images, in X-ray light, of a quasar some 6 billion light years away can be seen. By combining data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton Observatory, scientists were able to measure the (rapid) spin of the quasar's central supermassive black hole. This is one of many pieces of evidence supporting the existence of black holes, which leave no good alternative.

Credit: X-ray: NASA/CXC/University of Michigan/RCReis et al; Optical: NASA/STScI

The emitted dipole jets of particles and radiation stream energy outward into the universe.

Relativistic Jet Black Hole Galaxy Hercules A

While distant host galaxies for quasars and active galactic nuclei can often be imaged in visible/infrared light, the jets themselves and surrounding emissions are best seen in both X-ray and radio, as here the galaxy Hercules is shown for A. A black hole is needed to power an engine like this, but that does not mean that it is matter/radiation emanating from inside the event horizon.

Credit: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

However, our galaxy's central black hole is not completely silent.

MW Radio lobes

Even the Milky Way, a relatively quiet galaxy with a relatively small central supermassive black hole, displays giant geysers of charged particles emanating from the galactic center. They can be revealed by radio telescopes, such as this image produced from data from the Parkes radio telescope, aka the Dish.

Credit: A. Mellinger (C. Michigan), E. Caretti (CSIRO), S-PASS Team, E. Bressart (CSIRO)

X-ray flares show the galactic center occasionally “snacking” on matter.


Sagittarius A*, the supermassive black hole at the center of our galaxy, emits X-rays due to various physical processes. The flares we see in X-rays indicate that matter flows onto the black hole unevenly and non-continuously, causing the flares we see over time.

Credit: NASA/CXC/Amherst College/D.Haggard et al.

The massive, low-density Fermi bubble extends ~25,000 light years above and below the galactic plane.

energy injection fermi bubble

In the main image, our galaxy's antimatter jets are depicted, blowing 'Fermi bubbles' into the halo of gas around our galaxy. In the smaller, inset image, the actual Fermi data shows the gamma-ray emission produced by this process. These “bubbles” arise from the energy produced by electron-positron annihilation: an example of matter and antimatter interacting and converting into net energy via E = mc^2. We are certain that any antimatter signature in our galaxy does not originate from antimatter stars or large clusters of antimatter.

Credit: David A. Aguilar (Main); NASA/GSFC/Fermi (inset)

Within the galaxy center itself, magnetic fields shape the flow of matter and radiation.

galaxy center

Although the galactic center appears attractive in the lower-right portion of this image, even more puzzling are the visible “loopy” features that are evidence of filamentary strands of galactic magnetism. These non-thermal filaments have been theoretically predicted, but MeerKAT has identified and characterized them with unexpected and never-before-seen properties.

Credit: I. Haywood et al., 2022, ApJ

Stellar cataclysms – as well as young, massive stars – are common around Sagittarius A*.

galaxy center

This unprecedented view of the galactic center comes from the MeerKAT radio array in South Africa, and highlights never-before-seen features, including filaments, previously unseen bubbles and potentially even new supernova remnants and star-forming regions. Are.

Credit: I. Haywood et al., 2022, ApJ

How, then, is energy moved outward from the galactic center?

Infrared astronomical image shows various energy signatures in the galaxy, with annotations indicating distances and coordinates.

An At right) below the galactic center. In terms of distance/scale one parsec (pc) is approximately 3.26 light years.

Credit: SC Mackey et al., APJ submission, 2024

The answer has been revealed in the X-ray data: through a central “exhaust vent” within a chimney-like structure.

Two side-by-side astronomical images of a galaxy with a color spectrum, highlighting spatial data and differences in intensity within a section of the universe.

This linear X-ray emitting feature located within the southern part of the Galactic Center chimney suggests that a cylinder-shaped plasma outflow channel allows the outflowing material to shock/compress/heat the interstellar medium. A series of explosions can sustain this facility and others like it.

Credit: SC Mackey et al., APJ submission, 2024

The observed plasma outflow channels depart from the center of the galaxy.

galaxy center

This spectacular composite image, which combines X-ray, infrared and optical light from NASA's Great Observatories, was our best view of what's happening at the galactic center until 2009. However, over the past ~15 years, we have taken data that have revealed novel features that, at present, have not yet been fully explained. Protruding features above and below the galaxy's plane, perpendicular to it, indicate the transport of energy and gas in a chimney-like style.

Credit: NASA/JPL-Caltech/ESA/CXC/STScI

The explosions propel the material upwards, through the chimney and out: through this exhaust vent.

vent labeled

This image, composed of composite How to move away from the center.

Credit: X-Ray: NASA/CXC/Univ. Chicago/SC Mackey et al.; Radio: NRF/SARAO/MEERKAT; Image Processing: NASA/CXC/SAO/N. walk

Sequential accretion events probably maintain this structure over long time scales.

Annotated map of the center of the Milky Way at multiple wavelengths with regions and sources identified.

This image shows the magnetic galaxy center, with various features highlighted, as imaged by the SOFIA/HAWC+ FIREPLACE survey team. The giant bubble on the left of the image is about 30 light-years wide, several times larger than any other supernova-blown bubble discovered so far.

Credit: D. Pare et al., arXiv:2401.05317v2, 2024

At last, energy transport within the center of the galaxy was finally understood.


This updated radio/X-ray composite from the Galactic Centre, featuring data from both MeerKAT and Chandra, demonstrates the new information that can be gained from combining multiple wavelengths of light. In the future, better observations and better observatories may help us solve scientific mysteries of the origin of various features, including lobes, bubbles, and sprites.

Credit: X-ray: NASA/CXC/UMass/QD Wang; Radio: NRF/SARAO/MEERKAT

Mostly Mute Monday tells an astronomical story in images, visuals, and more than 200 words.

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