天王星和海王星可能并非“冰巨星”

Uranus and Neptune may not be ‘ice giants’ after all A growing number of theories propose Uranus and Neptune are rocky worlds HANNAH RICHTER For decades, elementary students learned the same tale of the Solar System: first come rocky terrestrial planets such as Earth, followed by gas giants such as Jupiter and ice giants such as Neptune, with lovable Pluto bringing up the rear. Then 20 years ago, planetary scientists downgraded Pluto to a “dwarf planet.” And now, they say, it’s time to revisit our idea of Neptune and Uranus, too—for the so-called ice giants likely contain very little ice. The term is “a little bit misleading,” says Ravit Helled, a planetary scientist at the University of Zürich. …