NASA’s Chandra notices venting galactic center

The chimney and vent are about 26,000 light-years from Earth.

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Astronomers using NASA’s Chandra X-ray Observatory have discovered an exhaust vent connected to a “chimney” of hot gas escaping the center of the Milky Way galaxy.

According to scientists, this chimney and exhaust vent may have been created by eruptions from the supermassive black hole at the Milky Way‘s center called Sagittarius A* (Sgr A* for short).

There are roughly 26,000 light-years between Earth and the chimney and vent. Starting from the galaxy’s center, the chimney is oriented perpendicularly to the spiral disk of the Milky Way. Astronomers have previously located the chimney using X-ray data from Chandra and XMM-Newton, an ESA (European Space Agency) mission with NASA support. Magnetic fields enveloping the chimney gas are evident in the radio emission picked up by the MeerKAT radio telescope.

The most recent Chandra data shows several X-ray ridges roughly perpendicular to the galaxy’s plane. Scientists believe these are the walls of a tunnel similar to a cylinder that helps direct hot gas away from the Galactic Center and upward along the chimney. About 700 light-years from the galactic center, the recently found vent is close to the chimney’s top.

Scott Mackey of the University of Chicago, who led the study, said, “We suspected that magnetic fields are acting as the walls of the chimney and that hot gas is traveling up through them, like smoke. Now we’ve discovered an exhaust vent near the top of the chimney.”

This exhaust vent is believed to have been formed after hot gas rising through the chimney struck more excellent gas lying in its path. The shock waves from this impact, which resemble the sonic booms from supersonic flights, give the exhaust vent walls their brilliance in X-rays. Because the gas traveling upwards is striking the tunnel wall at a more direct angle and with greater force than in other places, the left side of the exhaust vent is probably exceptionally bright.

According to the study’s authors, the heated gas is most likely the result of material falling into Sgr A*, followed by eruptions from the black hole that pushes the gas higher along the chimney and out the exhaust vent. However, they are unsure of the precise frequency of feeding the black hole.

Co-author Mark Morris of the University of California, Los Angeles, said, “We’re not sure if this energy and heat are stoked by a large amount of material being dumped onto Sgr A* at once, like a bunch of logs being dumped on a fire. Or it might come from multiple small loads fed into the black hole like kindling being regularly tossed in.”

The particles and energy in the vent offer hints regarding the origin of two enigmatic and considerably larger structures around the core of the Milky Way: the eROSITA Bubbles, found by ESA’s newest X-ray telescope, and the Fermi Bubbles, spotted in gamma-rays by NASA’s Fermi Gamma-ray Space Telescope. These two sets of formations are thousands of light-years apart from the galactic center. They offer valuable insights into previous explosive events near the galaxy’s center.

The direction of the chimney and another X-ray chimney that starts at the galaxy’s center and points in the opposite direction are aligned with the Fermi and eROSITA bubbles. The hot gas traveling upward may be concentrated by the exhaust outlet near the top of the chimney’s funneling effects, which could help the bubbles form a coherent structure.

Co-author Gabriele Ponti of the Italian National Institute of Astrophysics in Merate said“The origin of the Fermi Bubbles and the eROSITA bubbles are some of the biggest mysteries faced by studies of the high energy radiation from our galaxy. We’ve discovered a small structure that might play a large role in the creation of these gigantic bubbles.”

Journal Reference:

  1. Scott C. Mackey et al., X-Rays from a Central “Exhaust Vent” of the Galactic Center Chimney, The Astrophysical Journal Letters (2024). DOI: 10.3847/2041-8213/ad3248

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