WASHINGTON—Some people are two-faced, figuratively speaking of course. The ancient Roman god Janus was two-faced, literally—with one looking forward and another backward, representing transitions and duality. But a two-faced star? Yes, indeed.
Scientists have observed a white dwarf star—a hot stellar remnant that is among the densest objects in the cosmos— that they have nicknamed Janus owing to the fact it has the peculiar distinction of being composed of hydrogen on one side and helium on the other.
