Two Comets and a Star Cluster.

Two unusual spots are on the move near the famous Pleiades star cluster. Shifting only a small amount per night, these spots are actually comets in our nearby Solar System that by chance wandered into the field of the light-year s distant stars. On the far left is comet C/2017 O1 ASAS-SN, a multi-kilometer block of evaporating ice sporting a bright coma of surrounding gas dominated by green-glowing carbon. Comet ASAS-SN1 shows a slight tail to its lower right. Near the frame center is comet C/2015 ER61 PanSTARRS , also a giant block of evaporating ice , but sporting a rather long tail to its right. On the upper right is the Pleiades , an open cluster dominated by bright blue stars illuminating nearby reflecting dust . This exposure, taken about two weeks ago, is so deep that the filamentary interstellar dust can be traced across the entire field . The Pleiades is visible to the un aided eye , but it should require binoculars to see the comets .