Gamma ray mystery at heart of Milky Way

The Fermi Gamma-ray Space Telescope detected the structure that spans 50,000 light years, covers half the visible sky and may be millions of years old, a NASA release said Tuesday.

"What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center," says Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

"We don't fully understand their nature or origin," he says.
The structure's shape and emissions suggest it was formed as a result of a large and relatively rapid energy release, the source of which remains a mystery.

"In other galaxies, we see that star bursts can drive enormous gas outflows," David Spergel, a scientist at Princeton University in New Jersey, says. "Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics."

Scientists say they are conducting more analyses to better understand how the never-before-seen structure was formed.

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