Probing the mysterious Fermi bubbles that emanate from our galaxy

Science : Since 2010 scientists have known that material is outgassing from the core of the Milky Way, forming two giant lobes of plasma above and below the galactic plane. However, the cause of the so-called Fermi bubbles remains unknown. Now researchers report in Astrophysical Journal Letters that they have measured the speed of the outflowing gas via UV absorption-line spectroscopy from the Hubble Space Telescope. Light from a distant quasar shining through the base of the northern Fermi bubble is absorbed by carbon and silicon atoms, whose motion causes a Doppler shift. From the size of the shift the researchers have determined that the speed of the outflow is 900–1000 km/s and that it started about 2.5 million to 4.0 million years ago. Although the researchers remain in the dark as to how the bubbles formed, further data gathered through the use of some 20 additional quasars that lie behind other parts of the Fermi bubbles may provide additional clues.