Far above the Milky Way’s glowing centre, two giant bubbles stretch into space like a cosmic hourglass. But what scientists just found inside them is even more surprising than their size.
Chilled Gas Discovered in Scorching Galactic Bubbles
Astronomers using the Green Bank Telescope in West Virginia have spotted massive clouds of cold hydrogen gas hiding within the Fermi bubbles. These balloon-shaped structures, made of superheated plasma, rise above and below our galaxy’s core and span 50,000 light-years.
The hydrogen clouds, found about 13,000 light-years above the galactic centre, are chillingly cold compared to their sizzling surroundings. This contrast is puzzling, as such fragile clouds should not last long inside the extreme heat.
Experts believe the clouds are leftovers from much larger structures. These were likely pushed out from the galactic centre during a powerful outflow millions of years ago. Their survival hints at something much more recent than previously thought—a fierce event in our galaxy’s heart.
A Cosmic Clock Ticking in the Fermi Bubbles
Lead researcher Rongmon Bordoloi compared the clouds’ survival to ice cubes in boiling water. Small ones vanish fast, he said, but larger ones linger, even as they fade. The cold gas clouds, ranging from 13 to 91 light-years wide, may have once been even bigger.
Their continued presence could serve as a kind of clock. The clouds’ existence suggests the Milky Way’s central black hole may have erupted just a few million years ago. That, in cosmic terms, is almost like yesterday.
Discovered in 2010, the Fermi bubbles remain visible only in gamma rays. They also overlap with the X-ray-bright eROSITA bubbles. Both are thought to be products of ancient jets blasted out from the black hole.
Now, thanks to these cold gas clouds, scientists have a new clue. It’s clear the galaxy’s centre may still flare up from time to time, and much more recently than once believed.
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