FILE PHOTO: An artist’s concept shows the two-faced white dwarf star nicknamed Janus. The blue-tinted dead cinder of a star, which was once a star like our sun, is composed primarily of hydrogen on one side and helium on the other (the hydrogen side appears brighter). On the helium side, which appears bubbly, convection has destroyed the thin hydrogen layer on the surface and brought up the helium underneath. K. Miller, Caltech/IPAC/Handout via REUTERS. File Photo