Astronomers Confirm a New Class of Binary Stars


ELM white dwarf star


In about 5 billion years, our Sun will expand to become a red giant, lose its hydrogen-rich envelope, and leave behind a white dwarf star, which is the compact remnant core with about half the original mass of our Sun. In rare instances, a star can become an extremely low mass (ELM) white dwarf. Less than one-third the mass of the Sun, these stars present a conundrum: if stellar evolution calculations are correct, all ELM white dwarfs would seem to be more than 13.8 billion years old—older than the age of the universe itself and thus, physically impossible.