B Found: The Least Luminous Galaxy Ever Seen

[CygnusX-1]

Lying 280,000 light-years from Earth, the Virgo I galaxy emits only 180 times as much light as the Sun, half as much as the previous faint-galaxy champ. The galaxy's proximity to the Milky Way suggests that our Galaxy has hundreds of other satellite galaxies.

New Scientist has the exclusive story: New Scientist: Super-dim galaxy may be one of hundreds orbiting the Milky Way.

 

[Chronos]

It has been suggested that faint dwarf galaxies could account for the disparity between simulation predictionss and the actual numbers of observed MW satellite galaxies. There are most certainly more faint galaxies exist awaiting discovery, but, fewer than expected because the temperature of dark matter [which is fiendishly difficult to measure] could be warmer than assumed in the models. For discussion, see https://arxiv.org/abs/1506.03789, Structure formation in warm dark matter cosmologies: Top-Bottom Upside-Down.

 

[Drakkith]

the Virgo I galaxy emits only 180 times as much light as the Sun

Wow... That's really low.

 

[CygnusX-1]

Yes. A typical red giant star emits roughly 100 solar luminosities. So, as the New Scientist article states, when just one red giant becomes a white dwarf, such a dim galaxy can lose MOST of its light.

 

[CygnusX-1]

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