spaceweather.com -- A fresh comet is swinging through the inner solar system, and it is brightening rapidly as it approaches Earth for a 100 million mile close encounter in mid-June. Comet McNaught (C/2009 R1) has a vivid green head and a long wispy tail that look great through small telescopes. By the end of the month it could be visible to the naked eye perhaps as bright as the stars of the Big Dipper. Because this is the comet's first visit to the inner solar system, predictions of future brightness are necessarily uncertain; amateur astronomers should be alert for the unexpected. Visit spaceweather.com for sky maps, photos and more information.