Three giant stellar streams have been discovered arcing high over the Milky Way. Remnants of cannibalized galaxies and star clusters, the streams are between 13, 000 and 130, 000 light-years distant from Earth and extend over much of the northern sky. Two of the newly discovered streams are almost certainly the remains of ancient star clusters. Known to astronomers as globular clusters, these giant stellar cities contain between tens of thousands and millions of stars. Over billions of years, the relentless gravitational stresses inflicted on them by our galaxy have slowly torn them apart, leaving behind long, thin streams of stars. Once crowded so closely together that they could sometimes actually collide, these stars are now separated by many light-years, trailing one another at half a million miles an hour through the dark reaches of space. |