General Space Thread

If dark matter is "clumpy," then it's concentrated in irregular chunks distributed roughly across galaxies — much like the luminous matter we see concentrated in stars and nebulae. Some alternative theories, including theories that suggest dark matter doesn't exist at all, wouldn't include any clumps — and would have the effects of dark matter distributed smoothly across galaxies.



So far, Bonaca's discovery is one of a kind, so new that it hasn't yet been published in a peer-reviewed journal (though it was met appreciatively by the crowd of physicists at the prestigious conference).



To pull it off, she relied on data from the Gaia mission, an European Space Agency program to map billions of stars in our galaxy and their movements across the sky. It formed the best existing catalog of the stars that seem to be part of GD-1.



Bonaca buttressed that data with observations from the Multi Mirror Telescope in Arizona, which showed which stars were moving toward Earth, and which were moving away. That helped distinguish between stars that were really moving with GD-1, and those that just sat next to it in Earth's sky. That effort produced the most precise image ever of GD-1, which revealed the second gap, the spur, and a previously unseen region of the stellar stream.



Down the road, Bonaca said, she wants to do more mapping projects to reveal other regions of the sky where something unseen seems to be knocking stars around. The goal, she said, is to eventually map clumps of dark matter all across the Milky Way.