He studied comets, variable stars, galaxies and the evolution of the universe.

Let's get across why it's important to study comets even if you can't see them.

He discovered a number of asteroids, and also studied comets.

For scientists who study comets, that is perhaps the question.

The instrument has been used to study our galaxy, asteroids and comets.

Soviet scientists talk openly of their plans for missions to Mars and to study comets and asteroids.

"There's all kinds of excellent new equipment for studying comets," Hamner said.

Actually I like asteroids, but somebody has to study comets.

So far they have told me to study comets.

They arrive 839 minutes later, and they tell me to stop studying comets immediately.