Modified Gravity Could Soon Be Ruled Out, Says New Research On Dwarf Galaxies
“The fact that these two galaxies exhibit such different gravitational effects tell us that either something is very funny with one of them (something must be out-of-equilibrium), or that dark matter gets heated up by star formation and modified gravity cannot explain this. As always, more data, additional galaxies, and further research will be required to solve this mystery, but at long last, we’re looking at a viable way to prove modified gravity wrong on galaxy scales. Even without directly detecting a particle, dark matter might just achieve a knockout blow over its greatest competing alternative.”
If you have two galaxies in the Universe that look the same, you’d expect them to behave the same. After all, the laws that govern them ought to be identical, and so if their properties are identical, so should their behavior. The Draco and Carina dwarf galaxies are roughly the same mass, the same size, and have the same distribution of starlight. The only discernible difference is that one galaxy has only old stars, while the other has a mix of old and new stars. And yet, when we look at the gravitational effects of the mass on the stars, their behaviors are incredibly different. One seems to indicate a large unseen mass source in the center, and the other doesn’t.
In modified gravity, this makes no sense. But in dark matter theories, simple heating due to star formation could explain it all. Keep your ear to the ground, because this could lead to the death-knell for modified gravity!