Astronomy Picture of the Day

Explanation: Have you ever seen an aurora? Aurorae are occurring again with increasing frequency. With the Sun being unusually dormant over the past three years, the amount of Sun-induced aurorae has also been unusually low. More recently, however, our Sun has become increasingly active and exhibiting a greater abundance of sunspots, flares, and coronal mass ejections. Solar activity like this typically expels charged particles into the Solar System, some of which may trigger Earthly aurorae. As this year unfolded, the above timelapse displays of picturesque aurorae were captured above Tromsø, Norway. Curtains of auroral light, usually green, flow, shimmer and dance as energetic particles fall toward the Earth and ionize air molecules high up in the Earth's atmosphere. With solar maximum still in the future, there may be opportunities to see spectacular aurora personally over the next three years.