ASTRONOMY American astronomers using the Fermi Gamma-ray Space Telescope, which is designed to measure high-energy radiation in space, have discovered two giant bubbles centered in the Milky Way. The two bubbles, which emit gamma rays, each stretch 25,000 light-years from the center of the galaxy; the 50,000 light-years covered equal half of the visible sky.

Now, astronomers are trying to find out what could have generated such colossal structures. One suggestion is that the bubbles are the remains of a so-called jet coming from the black hole at the center of the Milky Way. Another idea posits that the bubbles are radiation from gases released into the universe in connection with the creation of star clusters at the center of the galaxy millions of years ago.