英语听力精选进阶版 13226（在线收听）

Lonely planets

Vocabulary

gas giants

large planets which don't have a solid surface

rogue

unconventional, not normal

came into being

were formed, created

cast-outs

objects that have been thrown away

ejected from

thrown out of

gravitational forces

the natural attraction that pulls objects in space together

interplanetary collisions

crashes between planets

Strictly speaking

Being accurate

the remains of

what is left of

orbs

round, ball-shaped objects