Giant “Gamma-Ray Bubbles” Discovered at the Center of the Milky Way Galaxy
Perhaps we spoke too soon about the Milky Way galaxy’s thinness: NASA scientists have discovered two enormous “gamma-ray-emitting bubbles” which appear to emanate from the center of the galaxy, each extending 25,000 light years “north and south of the galactic center.” The Milky Way has a diameter of about 100,000 light years in total, and the structure covers more than half of the visible sky.
According to USA Today, “each one emits the energy of about 100,000 exploding supernova stars.”
There’s not yet a clear consensus as to how these structures were formed, but the current hypothesis is that they may have stemmed from a black hole explosion some millions of years ago:
One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way’s black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many 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.”
Today happens to be Carl Sagan’s birthday, incidentally.