Attempts to modify gravity to achieve late time cosmic acceleration
usually run into already stringent solar system constraints on general
relativity (GR). Recently, it was realized that one can evade these
constraints via "screening" -- one constructs theories where the
effective gravity is dependent on ambient gravitational potential,
hence since the solar system is embedded in a deep potential well of
the Milky Way and local Group, GR is restored. Meanwhile at
cosmological scales, gravity can be modified to resemble dark energy.
Such theories include the venerable f(R) gravity theory, and the more
recent trendy models such as the Chameleon and the Symmetron.
I will show that modified gravity will change the stellar structure
equations dramatically in dwarf galaxies not associated with clusters.
Stars in these galaxies are generically hotter and more luminous, and
live much shorter lives as a result. Not only are the galaxies then
brighter, they are also bluer -- allowing us to put new bounds
modified gravity by an order of magnitude or more.
