Above the Mysterious Fog Surrounding the Milky Way

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The center of our galaxy, the Milky Way, is home to a supermassive black hole surrounded by clusters of young stars and giant molecular clouds.

As these young stars and clouds swirl around the black hole, some are inevitably devoured, releasing enormous jets of high energy x-rays, gamma rays and cosmic rays.

The history of our galaxy is full of such events, although today, the black hole appears quiescent.

On November 9th, 2010, a group of scientists at NASA's Fermi Gamma-Ray Space Telescope announced the discovery of two bubbles of energy erupting from the center of our galaxy. The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be have been around for millions of years.

These bubbles extend 25,000 light years from each side of our galaxy and contain the energy equivalent of 100,000 supernovae.

Astronomers hadn't detected them sooner partly because of a fog of gamma rays that appears throughout the sky. This fog is the result of highly energetic particles moving near the speed of light and interacting with interstellar gas in the Milky Way. By using various estimates of the fog, astronomers were able to isolate and subtract it, unveiling the giant bubbles.

This discovery came as a complete surprise - no one had any idea they were there, and their source is a mystery. One possibility is that these bubbles are fueled by waves of star birth at the galactic center.

Another idea is that they are the result of gigantic, periodic outbursts from the massive black hole.

The center of our galaxy is home to all manner of strange high-energy phenomena including, not only a massive black hole, but violently spinning pulsars, and possibly even showers of cosmic rays produced from the collisions of dark matter.

Whatever their source, these bubbles are another indication that our home galaxy, our own celestial backyard, yet holds many mysteries.