Astronomers tallying up all the normal matter—stars, galaxies and gas—in the universe today have come up embarrassingly short of the total matter produced in the Big Bang 13.6 billion years ago. In fact, more than half of normal matter—half of the 15% of the universe's matter that is not dark matter—cannot be accounted for in the glowing stars and gas we see.
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    0•12 days ago

    Astronomers have generally thought that massive black holes at the centers of galaxies expel gas in jets of material only during their formative years, when the central black hole is gobbling up gas and stars and producing lots of radiation. This makes them stand out as what astronomers call active galactic nuclei (AGN), or quasars.

    If, as the new study suggests, the ionized hydrogen halo around galaxies is more diffuse, but also more extensive, than thought, this implies that the central black holes may actually become active at other times in their lives.

    I love how we keep finding more and more about the role that black holes play in our universe.