More than 180 million km from Earth, something is happening to Comet PanSTARRS (C/2015 ER61). On April 4th and 5th, the comet brightened more than 6-fold, from magnitude +8.5 to +6.5, suddenly reaching the verge of naked-eye visibility despite its great distance from our planet. Now amateur astronomers are photographing an incredible tail. Gerald Rhemann sends this picture from his private observatory in Farm Tivoli, Namibia: "The comet's tail is about 2.5 degrees long," says Rhemann. That means it spans more than 8 million km. For comparison, the entire sun is 1.4 million km wide; you could wrap the comet's tail around the sun's equator twice. Another way of putting it: The distance from Earth to the Moon is only 5% of the length of the gaseous lane behind Comet PanSTARRS. The comet's outburst is probably caused by a fresh vein of icy material in the comet's nucleus exposing itself to solar radiation. Furiously vaporizing, the comet's core is spewing jets of dust and gas into space-