NASA | STScI | HubbleSite | 2019 Oct 17
Dark matter tugs the most massive spiral galaxies to breakneck speeds
You’ve probably never noticed it, but our solar system is moving along at quite a clip. Stars in the outer reaches of the Milky Way, including our Sun, orbit at an average speed of 130 miles per second. But that’s nothing compared to the most massive spiral galaxies. “Super spirals,” which are larger, brighter, and more massive than the Milky Way, spin even faster than expected for their mass, at speeds up to 350 miles per second.Credit: NASA, ESA, SDSS, P. Ogle and J. DePasquale (STScI)
Their rapid spin is a result of sitting within an extraordinarily massive cloud, or halo, of dark matter – invisible matter detectable only through its gravity. The largest “super spiral” studied here resides in a dark matter halo weighing at least 40 trillion times the mass of our Sun. The existence of super spirals provides more evidence that an alternative theory of gravity known as Modified Newtonian Dynamics, or MOND, is incorrect.
A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass ~ Patrick M. Ogle et al