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| Fermi Bubbles of our Milky Way |
In Outer Diverse, the first book of the space
thriller trilogy The Splintered Universe, Detective Rhea Hawke travels through the dangers “breathing” galaxies and dark
matter in her quest for justice:
When I’d joined up as an Enforcer, the Guardians gave me my own starship, a rare ray-class retro Earth/alien design that no one else wanted. It didn’t matter to me. Benny was mine. Thanks to Benny’s plasma shields, we’d weathered treacherous ionic storms, gamma-ray bursts, and the high-velocity clouds of the breathing galaxy. We jacked the Magellanic Stream and travelled to the farthest arms of the spiral galaxy, surfing scalar fields into thrilling particle stream shortcuts. We’d even slingshot our way around the black hole in the galactic core using its immense gravitational field and high-energy emissions. I’d witnessed many galactic wonders like the terrifying beauty of nebulas: tangled filaments of dust and ionized gas that poured out in jets and waves from the stellar corpse of a neutron star. Pulsing electromagnetic energy, the shock wave of material flung from the supernova created a spectacular lightshow that shredded anything in its path, drawing me into breathless wonder …
The stuff of
science fiction isn’t always fiction. Was Rhea Hawke talking about the Fermi
About four
years ago, NASA revealed an incredible structure discovered by astronomers at
their Fermi Gamma-ray Space Telescope. Spanning 50,000 light-years and
extending north and south of the Milky Way’s centre like a giant infinity
symbol, the gargantuan gamma ray bubbles—now called the Fermi Bubbles—are
speculated to be the remnants of an eruption from a supersized black hole at
the centre of our galaxy.
“The outlines of the
bubbles are quite sharp, and the bubbles themselves glow in nearly uniform
gamma rays over their colossal surfaces, like two 30,000-light-year-tall
incandescent bulbs screwed into the center of the galaxy,” Stanford scientists and the Department of Energy's SLAC National Accelerator Laboratory reported in
an April 2014 paper in The Astrophysical Journal. Their size is another
puzzle. The farthest reaches of the Fermi bubbles contain some of the highest
energy gamma rays, but there's no discernable cause for them that far from the
galaxy. Another difference from other galactic bubbles is that the parts of the
bubbles closest to the galactic plane shine in microwaves as well as gamma
rays, but at about two-thirds of the way out, the microwaves fade out and only
gamma rays are detectable.
“Gamma rays
are the bad boys of the electromagnetic spectrum—the highest energy light in
the universe,” says Bob Berman of the Almanac Weekly. “Because of this, they do not reliably
reflect off objects the way that visible light does. Rather, they are
penetrating. Such photons drill through bodies at the speed of light, damaging
chromosomes all along the way.” The hour-glass shaped structure spans more than half of the
visible sky, from the constellation Virgo to the constellation Grus, and it may
be millions of years old.
Doug Finkbeiner
and his team at the Harvard-Smithsonian Center for Astrophysics in Cambridge,
Mass discovered the bubbles by processing publicly available data from Fermi's
Large Area Telescope (LAT). The LAT is the most sensitive and
highest-resolution gamma-ray detector ever launched.
The bubble
emissions have a well-defined shape and are much more energetic than the
gamma-ray fog seen elsewhere in the Milky Way, suggesting that it was formed from
a large and rapid energy release - the source of which remains a mystery.
“Fortunately,
few gamma rays reach us here at Earth’s surface,” Berman continues. “Stars
usually don’t emit them, and in any case our atmosphere blocks them. The only
gamma rays flying near Earth have come from distant violent events like
supernovae. This is why a dense gamma-ray swarm at our own galaxy’s center is
so puzzling. It’s the unmistakable sign of extreme violence. And yet, these
days, the Milky Way’s core is about as energetic as a steamy Florida
lunchtime.”
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| A giant "burp" from a black hole...? |
What Blew the Bubbles?
NASA speculates that the bubbles could have
been created by huge jets of accelerated matter blasting out from the
supermassive black hole at the center of our galaxy. Or
they may have formed as gas outflows from a burst of star formation, perhaps
the one that created the massive star clusters in the Milky Way's center
several million years ago.
"In
other galaxies, we see that starbursts can drive enormous gas outflows,"
said David Spergel, a scientist at Princeton University in New Jersey. "Whatever the energy source behind these
huge bubbles may be, it is connected to many deep questions in
astrophysics."
Berman asks,
“Might these be the long-sought signs of dark matter? Could dark matter be
meeting its opposite entity (whatever that is) in total annihilation, the way that
matter and antimatter do?” As Fermi research team leader Douglas Bookbeiner put
it, “This just confuses everything.” Except the science fiction writers (smug
grin).
For more
information about Fermi, visit:
http://www.nasa.gov/fermi
Nina Munteanu is an ecologist and internationally published author of novels, short stories and essays. She coaches writers and teaches writing at George Brown College and the University of Toronto. For more about Nina’s coaching & workshops visit www.ninamunteanu.me. Visitwww.ninamunteanu.ca for more about her writing.
