Clouds of star-forming gas are being shot 'like bullets' across the galaxy
Astronomers are still looking for the "smoking gun" that blasted these clouds through space.
There's a flood of scorching nuclear wind pouring out of our galaxy's center, and astronomers have discovered two tiny islands of unborn baby stars caught in the riptide.
These two hunks of cosmic driftwood are actually freezing-cold clouds of hydrogen gas, each one as frigid as Pluto (about minus 400 degrees Fahrenheit, or minus 240 degrees Celsius) and carrying the mass of more than 200 suns. In calmer waters, they could be stellar nurseries — those ultra-dense clouds of gas where molecules can bundle up into stars. However, the searing winds of the galactic center seem to have other plans for them, a new study published Aug. 19 in the journal Nature suggests.
Flying "like bullets" away from the galactic center, the two tiny clouds of gas seem to be colliding head-on with hotter, more energetic winds from the galaxy's heart, according to the study. This ongoing collision threatens to dismantle the gas clouds entirely, smothering their star-forming potential.
Related: 11 fascinating facts about our Milky Way galaxy
"Galaxies can be really good at shooting themselves in the foot," study co-author Naomi McClure-Griffiths, an astrophysicist at The Australian National University (ANU), said in a statement. "When you drive out a lot of mass, you're losing some of the material that could be used to form stars, and if you lose enough of it, the galaxy can't form stars at all anymore."
Cold gas clouds are rare in the modern Milky Way, and especially within the vast central domain of the galaxy's nuclear winds, the researchers said. These two gas clouds sit toward the base of the Fermi Bubbles — two gargantuan orbs of hot gas and cosmic rays that tower 25,000 light-years over each side of the galactic center (for comparison, the entire Milky Way is only about 100,000 light-years in diameter).
Scientists have linked the Fermi Bubbles to a mighty outburst of energy from the galaxy's central black hole, which occurred millions of years ago. All these millennia later, those gassy blobs are still blazing hot, measuring more than 10,000 F (5,700 C) — far too hot for star formation.
How the newly-discovered gas clouds ended up inside those inhospitable bubbles is still a mystery, the authors of the new study said. Elsewhere in the universe, it's not unusual for star-forming material to get swept through space by jets from an active supermassive black hole, or to be shunted by solar winds blowing out of the densely packed stars near a galaxy's center. But the Milky Way's central black hole has not been active for a long time, the researchers said, nor does it contain enough stars near its center to create the sort of kick needed to send the gas clouds soaring.
"We don't know how either the black hole or the star formation [in the Milky Way] can produce this phenomenon," lead author Enrico Di Teodoro of Johns Hopkins University said in the statement. "We're still looking for the smoking gun, but it gets more complicated the more we learn about it."
Hopefully, further observations will reveal how these cool clouds got punted into the cosmic inferno.
Originally published on Live Science.
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Brandon is the space/physics editor at Live Science. His writing has appeared in The Washington Post, Reader's Digest, CBS.com, the Richard Dawkins Foundation website and other outlets. He holds a bachelor's degree in creative writing from the University of Arizona, with minors in journalism and media arts. He enjoys writing most about space, geoscience and the mysteries of the universe.
By Kiley Price