BRAIN DUMP

Is there an upper limit to the size of a star?

Xinyi Zhou

■ Astronomers believe the maximum size a star can grow to is 150 times the mass of our Sun. There are more massive stars, but they have been formed by two or more stars merging together. JS

Is there an animal that doesn’t sleep?

Adrian Manson

■ This depends on your definition of sleep. Bullfrogs appear to have short periods of sleep throughout the day, but when scientists tested their responsiveness, they reacted just as quickly when they were asleep as when they were awake. This suggests they weren’t technically sleeping but just in a state of rest. JS

Who was Charles Darwin, and what did he have to do with the theory of evolution?

Brittney Graham

■ The British naturalist’s theory of evolution explained how life adapts and diversifies over time. Darwin’s revolutionary ideas were born out of a five-year voyage around the