Among the hundreds of billions of galaxies that stretch across the known universe, even the smallest members can reveal secrets about our cosmic history. But even as we discover new galaxies, astronomers suspect that many small "dwarf" galaxies remain hidden from view. Only a fraction of the size of the Milky Way, these galaxies have thus far been too faint for most telescopes to spot. But a new survey has uncovered dozens of these elusive dwarf systems, often found in swarms orbiting much larger galactic hosts.
Because these dwarf galaxies are unusually sensitive to the underlying physics of the universe, finding a rich trove of them is a powerful way to test competing theories of how the universe is built and how dark matter behaves across different scales in the universe. Their weak internal gravity makes them particularly responsive to external influences, especially the gravitational pull of larger neighboring galaxies. In addition to helping us understand how galaxies form, these interactions can help scientists glean vital information about dark matter — a hypothetical, invisible substance that is thought to make up a significant portion of the universe's mass and energy.
