This artist's concept shows the two-faced white dwarf 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). The peculiar double-faced nature of this white dwarf might be due to the interplay of magnetic fields and convection, or a mixing of materials. On the helium side, which appears bubbly, convection has destroyed the thin hydrogen layer on the surface and brought up the helium underneath. Credit: K. Miller, Caltech/IPAC In a first for white dwarfs, the burnt-out cores of dead stars, astronomers have discovered that at least one member of this cosmic family is two faced. One side of the white dwarf is composed of hydrogen, while the other is made up of helium.