habitable – adj. able to be lived in

light-year –n. (unit of measure) the distance light travels in one year

determine – v. discover the facts or truth about something

harbor – v. to be the home or habitat of

maintain – v. make a situation or activity continue

composition – n. the parts that something consists of

possess – v. to have or own something

motivate – v. to cause someone to behave a particular way

detect – v. to discover or notice something