Active Galaxy

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Science  15 Jun 2012:
Vol. 336, Issue 6087, pp. 1362
DOI: 10.1126/science.336.6087.1362-d

Like most other galaxies, the Milky Way hosts a massive black hole in its center. This hole is 4 million times more massive than the Sun, and although it currently lies dormant, it is expected that it experienced periods of activity as it grew by accreting gas and stars from its vicinity. Using data from the Fermi Large Area Telescope, Su and Finkbeiner report signs of that activity in the form of two gamma-ray jets, which emanate from the center of the Milky Way in nearly opposite directions. These jets are tilted at an angle of 15° from the north-south axis of the galaxy and extend to about the edge of two previously identified gamma-ray–emitting bubbles, which extend 27,000 light-years north and south of the galactic center. The southern jet has blown a tenuous gamma-ray–emitting cocoon as it propagated through the interstellar medium. The shape of this cocoon is similar to those of the radio-emitting cocoons produced by the jets of actively accreting black holes in distant galaxies. It is not clear whether the bubbles and the jets and cocoon system were produced concurrently.

Astrophys. J. arXiv:1205.5852 (2012).

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