'Cosmic Rain' Stunts Galaxy Growth

Apparently proper hygiene is a bit different for growing galaxies, as a long "shower" could be a very bad thing. NASA's Chandra X-ray Observatory and Hubble Space Telescope have revealed a young galaxy cluster that is riddled with holes. Research now reveals that it's growth was stunted by its very own black hole after unusual cosmic precipitation halted an important cycle.

That's at least according to a recent analysis of galaxies that have "dried up," as published in the journal Nature. It builds upon work previously introduced at the start of this year in The Astrophysical Journal Letters, which details how galaxies traditionally stay cool enough to keep making stars.

You read that right; I said "cool." Apparently to make giant blazing balls of plasma, you need relatively cool dust and gases at a galaxy's core. Nature World News has previously reported how waves of hot gas can actually halt star formation in its tracks.

Given the right conditions, cosmic gas sometimes "gets hung up in a warm disk, shutting down star formation and probably frustrating the black hole's growth by being too turbulent at this point in time," researcher Philip Appleton, a project scientist for the NASA Herschel Science Center, explained in a past statement.

This latest work reveals more to that tale, showing in detail how galaxy health is regulated with the constant cooling of gas through radiation and energy loss - a process called "precipitation." The clouds of cool gas that result then help facilitate dense star nurseries and new star formation, even as some of it falls into a galaxy's central supermassive black hole

However, if too much cool gas reaches the black hole at once, it can prompt the creation of jets that heat a galaxy's gas and prevent further cooling. There then must be a balance in which these jets still occur but at a calmer level. That, in turn, prevents "showers" of cold gas from becoming too strong and triggering stronger jets.

The studies also revealed that some galaxies that prematurely halted in growth likely did so after being exposed to far too much cool or hot gas after a devastating galactic collision.

Still, there is hope for these unfortunate fledgling galaxies yet. According to NASA, the researchers also found that sometimes an "overshowered" galaxy may reset in a few hundred million years - a brief pause in the long life of a star-packed cluster.

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