Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
solar system – n. our sun and the planets that move around it
journal – n. a magazine that reports on things of special interest to a particular group of people
alien – adj. from somewhere other than the planet Earth
tidal – adj. of or relating to the regular upward and downward movement of the level of the ocean that is caused by the pull of the Sun and the Moon on the Earth
comet – n. an object in outer space that develops a long, bright tail when it passes near the sun
asteroid – n. any one of thousands of small planets that circle around the sun
disrupte(d) – v. to cause (something) to be unable to continue in the normal way
mutual – adj. shared between two or more people or groups
hypothesize(d) – v. to suggest an idea or theory
