This artist’s conception shows an edge-on view of our home galaxy, the Milky Way, with a couple of new features no one imagined before two years ago. Last month (May 2012), astronomers at the Harvard-Smithsonian Center for Astrophysics announced gamma-ray jets (shown in pink) extending for 27,000 light-years above and below the plane of the galaxy, where our sun and most of the Milky Way’s stars move in their vast orbits.
Previously known gamma-ray bubbles – the mind-boggling Fermi Bubbles – are shown in purple. The newly discovered jets, meanwhile, are tilted at an angle of 15 degrees. The Fermi telescope first discovered the vast Fermi Bubbles in 2010. They are extending above and below the plane of our Milky Way, and they shine in gamma rays and x-rays. Since our galaxy is known to have a supermassive black hole at its heart, it’s thought these Fermi Bubbles, shining at highly energetic wavelengths, might be the remnant of an eruption from that central black hole.
By the way, the Fermi Bubbles – and presumably these newly discovered jets as well – span more than half of the visible sky, from the constellation Virgo to the constellation Grus. In other words, when you look at the night sky, chances are you’re looking right at these bubbles and jets – but since your eyes can’t detect gamma rays or x-rays, you can’t see them.
The bubbles and jets suggest that our galactic center was much more active in the past than it is today.
Bottom line: Astronomers at the Harvard-Smithsonian Center for Astrophysics have added more to the emerging picture of energetic events that happened in our galaxy’s core, sometime in the past. They’ve found energetic jets, shining in gamma rays, in about the same location at the previously discovered Fermi Bubbles. Both extend tens of thousands of light-years above and below the Milky Way’s flat plane.