... Observing . ... Acceleron, anyone? Dark energy may arise from the interaction of neutrinos and a hypothetical particle. ... The main ingredient of the universe is "dark energy," a mysterious form of energy that exists between galaxies and forces the universe to expand at an ever-increasing rate. ... Only registered members of Astronomy.com are allowed to comment on this article. ... Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. ...