1.   In one case, a primeval blue galaxy appears in five different places in the sky, its image split by the steep curvature around a foreground galaxy cluster.

2.   More recently, Tyson and others examined the backdrop of blue galaxies through the lens of a cluster of galaxies seen with the Hubble Space Telescope.

3.   The existence of many faint blue galaxies has been known for decades, but the distribution and the nature of these galaxies remain subjects of debate.

4.   They noticed an unusually bright blue galaxy in the background of one of the images.