Stars like our sun fuse hydrogen in their cores into helium.
太阳一类的恒星在其核心将氢聚变成氦。
2
The finding also challenges theories of planet formation, which hold that stars need more than hydrogen and helium to produce planets.
这个发现同时也是对行星形成理论的一次挑战，该理论认为恒星需要更多的氢和氦才能形成行星。
3
Stars like our sun fuse hydrogen in their cores into helium. White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel.