NASA describes Eta Carinae as having a "volatile temperament," and as a doomed star, why shouldn't it be just a little moody? Here's how it has behaved in the last two centuries: "In 1843, Eta Carinae was one of the brightest stars in the sky. It then slowly faded until, in 1868, it became invisible in the sky. Eta Carinae started to brighten again in the 1990s and was again visible to the naked eye. Around 1998 and 1999, its brightness suddenly and unexpectedly doubled."
The arcs and streaks in galaxy cluster Abell 370 reveal "gravitational lensing," the distortion of light from far-off, background galaxies by the cluster's gravitational field. The lensing effect helps astronomers measure the distribution of dark matter in galaxy clusters.