60-Second Space

Milky Way Black Hole Had Hungry Past

A huge cloud of plasma south of our galactic black hole could be evidence of a past feeding frenzy. John Matson reports

The black hole at the center of the Milky Way is pretty mellow: well-fed and content. But that wasn’t always the case.

Black holes flare up when they consume large gulps of matter. The doomed material compresses and heats up around the exterior of the black hole, glowing brightly, including in x-ray light.

Researchers in Japan used an x-ray telescope on the Suzaku satellite to scan the region just south of our galaxy’s black hole. And they located what might be the remnant of a past feeding frenzy. The research appears in the Astrophysical Journal. [Shinya Nakashima et al., Discovery of the Recombining Plasma in the South of the Galactic Center: A Relic of the Past Galactic Center Activity?]

The researchers spotted a huge cloud of plasma, some 300 light-years long, containing highly ionized atoms. Supernovas could have energized the cloud, but it would have taken a lot of the exploding stars. The more dramatic possibility is that the Milky Way’s black hole flared up about 100,000 years ago, heating and ionizing the plasma cloud.

Recent studies have uncovered evidence for even more ancient black hole flare-ups, as well as outbursts as recently as 300 years ago. So it’s good to live far from the galactic center, way out on our peaceful spiral arm.

—John Matson

[The above text is a transcript of this podcast.]

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